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Could transfusion of a different blood type cure blood-based cancers?

Could transfusion of a different blood type cure blood-based cancers?


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Different antigen detection triggers an immune system response that could perhaps stimulate mitochondria and such in killing cancer cells - something like chemo without the hair-loss?


No. When a different blood type is introduced in the body, the host immune system recognizes the foreign blood as non-self and attacks it. The transfused blood becomes useless, and the potentially massive immune reaction can cause shock, which itself can be fatal.

More details in the book Blood Groups and Red Cell Antigens, which can be found at the NCBI library.


Blood mystery solved: Two new blood types identified

You probably know your blood type: A, B, AB or O. You may even know if you're Rhesus positive or negative. But how about the Langereis blood type? Or the Junior blood type? Positive or negative? Most people have never even heard of these.

Yet this knowledge could be "a matter of life and death," says University of Vermont biologist Bryan Ballif.

While blood transfusion problems due to Langereis and Junior blood types are rare worldwide, several ethnic populations are at risk, Ballif notes. "More than 50,000 Japanese are thought to be Junior negative and may encounter blood transfusion problems or mother-fetus incompatibility," he writes.

But the molecular basis of these two blood types has remained a mystery -- until now.

In the February issue of Nature Genetics, Ballif and his colleagues report on their discovery of two proteins on red blood cells responsible for these lesser-known blood types.

Ballif identified the two molecules as specialized transport proteins named ABCB6 and ABCG2.

"Only 30 proteins have previously been identified as responsible for a basic blood type," Ballif notes, "but the count now reaches 32."

The last new blood group proteins to be discovered were nearly a decade ago, Ballif says, "so it's pretty remarkable to have two identified this year."

Both of the newly identified proteins are also associated with anticancer drug resistance, so the findings may also have implications for improved treatment of breast and other cancers.

As part of the international effort, Ballif, assistant professor in the biology department, used a mass spectrometer at UVM funded by the Vermont Genetics Network. With this machine, he analyzed proteins purified by his longtime collaborator, Lionel Arnaud at the French National Institute for Blood Transfusion in Paris, France.

Ballif and Arnaud, in turn, relied on antibodies to Langereis and Junior blood antigens developed by Yoshihiko Tani at the Japanese Red Cross Osaka Blood Center and Toru Miyasaki at the Japanese Red Cross Hokkaido Blood Center.

After the protein identification in Vermont, the work returned to France. There Arnaud and his team conducted cellular and genetic tests confirming that these proteins were responsible for the Langereis and Junior blood types. "He was able to test the gene sequence," Ballif says, "and, sure enough, we found mutations in this particular gene for all the people in our sample who have these problems."

Transfusion troubles

Beyond the ABO blood type and the Rhesus (Rh) blood type, the International Blood Transfusion Society recognizes twenty-eight additional blood types with names like Duffy, Kidd, Diego and Lutheran. But Langereis and Junior have not been on this list. Although the antigens for the Junior and Langereis (or Lan) blood types were identified decades ago in pregnant women having difficulties carrying babies with incompatible blood types, the genetic basis of these antigens has been unknown until now.

Therefore, "very few people learn if they are Langereis or Junior positive or negative," Ballif says.

"Transfusion support of individuals with an anti-Lan antibody is highly challenging," the research team wrote in Nature Genetics, "partly because of the scarcity of compatible blood donors but mainly because of the lack of reliable reagents for blood screening." And Junior-negative blood donors are extremely rare too. That may soon change.

With the findings from this new research, health care professionals will now be able to more rapidly and confidently screen for these novel blood group proteins, Ballif wrote in a recent news article. "This will leave them better prepared to have blood ready when blood transfusions or other tissue donations are required," he notes.

"Now that we know these proteins, it will become a routine test," he says.

A better match

This science may be especially important to organ transplant patients. "As we get better and better at transplants, we do everything we can to make a good match," Ballif says. But sometimes a tissue or organ transplant, that looked like a good match, doesn't work -- and the donated tissue is rejected, which can lead to many problems or death.

"We don't always know why there is rejection," Ballif says, "but it may have to do with these proteins."

The rejection of donated tissue or blood is caused by the way the immune system distinguishes self from not-self. "If our own blood cells don't have these proteins, they're not familiar to our immune system," Ballif says, so the new blood doesn't "look like self" to the complex cellular defenses of the immune system. "They'll develop antibodies against it," Ballif says, and try to kill off the perceived invaders. In short, the body starts to attack itself.

"Then you may be out of luck," says Ballif, who notes that in addition to certain Japanese populations, European Gypsies are also at higher risk for not carrying the Langereis and Junior blood type proteins.

"There are people in the United States who have these challenges too," he says, "but it's more rare."

Other proteins

Ballif and his international colleagues are not done with their search. "We're following up on more unknown blood types," he says. "There are probably on the order of 10 to 15 more of these unknown blood type systems -- where we know there is a problem but we don't know what the protein is that is causing the problem."

Although these other blood systems are very rare, "if you're that one individual, and you need a transfusion," Ballif says, "there's nothing more important for you to know."


Researchers Discover Two New Proteins Responsible for Blood Type

Researchers at the University of Vermont have discovered two new proteins, ABCB6 and ABCG2, responsible for a basic blood type. This solves the mystery of the molecular basis of Langereis and Junior blood types and the findings may also have implications for improved treatment of breast and other cancers.

You probably know your blood type: A, B, AB or O. You may even know if you’re Rhesus positive or negative. But how about the Langereis blood type? Or the Junior blood type? Positive or negative? Most people have never even heard of these.

Yet this knowledge could be “a matter of life and death,” says University of Vermont biologist Bryan Ballif.

While blood transfusion problems due to Langereis and Junior blood types are rare worldwide, several ethnic populations are at risk, Ballif notes. “More than 50,000 Japanese are thought to be Junior negative and may encounter blood transfusion problems or mother-fetus incompatibility,” he writes.

But the molecular basis of these two blood types has remained a mystery — until now.

In the February issue of Nature Genetics, Ballif and his colleagues report on their discovery of two proteins on red blood cells responsible for these lesser-known blood types.

Ballif identified the two molecules as specialized transport proteins named ABCB6 and ABCG2.

“Only 30 proteins have previously been identified as responsible for a basic blood type,” Ballif notes, “but the count now reaches 32.”

The last new blood group proteins to be discovered were nearly a decade ago, Ballif says, “so it’s pretty remarkable to have two identified this year.”

Both of the newly identified proteins are also associated with anticancer drug resistance, so the findings may also have implications for improved treatment of breast and other cancers.

Cross-border science

As part of the international effort, Ballif, assistant professor in the biology department, used a mass spectrometer at UVM funded by the Vermont Genetics Network. With this machine, he analyzed proteins purified by his longtime collaborator, Lionel Arnaud at the French National Institute for Blood Transfusion in Paris, France.

Ballif and Arnaud, in turn, relied on antibodies to Langereis and Junior blood antigens developed by Yoshihiko Tani at the Japanese Red Cross Osaka Blood Center and Toru Miyasaki at the Japanese Red Cross Hokkaido Blood Center.

After the protein identification in Vermont, the work returned to France. There Arnaud and his team conducted cellular and genetic tests confirming that these proteins were responsible for the Langereis and Junior blood types. “He was able to test the gene sequence,” Ballif says, “and, sure enough, we found mutations in this particular gene for all the people in our sample who have these problems.”

Transfusion troubles

Beyond the ABO blood type and the Rhesus (Rh) blood type, the International Blood Transfusion Society recognizes twenty-eight additional blood types with names like Duffy, Kidd, Diego and Lutheran. But Langereis and Junior have not been on this list. Although the antigens for the Junior and Langereis (or Lan) blood types were identified decades ago in pregnant women having difficulties carrying babies with incompatible blood types, the genetic basis of these antigens has been unknown until now.

Therefore, “very few people learn if they are Langereis or Junior positive or negative,” Ballif says.

“Transfusion support of individuals with an anti-Lan antibody is highly challenging,” the research team wrote in Nature Genetics, “partly because of the scarcity of compatible blood donors but mainly because of the lack of reliable reagents for blood screening.” And Junior-negative blood donors are extremely rare too. That may soon change.

With the findings from this new research, health care professionals will now be able to more rapidly and confidently screen for these novel blood group proteins, Ballif wrote in a recent news article. “This will leave them better prepared to have blood ready when blood transfusions or other tissue donations are required,” he notes.

“Now that we know these proteins, it will become a routine test,” he says.

A better match

This science may be especially important to organ transplant patients. “As we get better and better at transplants, we do everything we can to make a good match,” Ballif says. But sometimes a tissue or organ transplant, that looked like a good match, doesn’t work — and the donated tissue is rejected, which can lead to many problems or death.

“We don’t always know why there is rejection,” Ballif says, “but it may have to do with these proteins.”

The rejection of donated tissue or blood is caused by the way the immune system distinguishes self from not-self. “If our own blood cells don’t have these proteins, they’re not familiar to our immune system,” Ballif says, so the new blood doesn’t “look like self” to the complex cellular defenses of the immune system. “They’ll develop antibodies against it,” Ballif says, and try to kill off the perceived invaders. In short, the body starts to attack itself.

“Then you may be out of luck,” says Ballif, who notes that in addition to certain Japanese populations, European Gypsies are also at higher risk for not carrying the Langereis and Junior blood type proteins.

“There are people in the United States who have these challenges too,” he says, “but it’s more rare.”

Other proteins

Ballif and his international colleagues are not done with their search. “We’re following up on more unknown blood types,” he says. “There are probably on the order of 10 to 15 more of these unknown blood type systems — where we know there is a problem but we don’t know what the protein is that is causing the problem.”

Although these other blood systems are very rare, “if you’re that one individual, and you need a transfusion,” Ballif says, “there’s nothing more important for you to know.”


Blood Test Could Spot Multiple Cancer Types, Researchers Say

WEDNESDAY, May 29, 2019 (HealthDay News) -- A gene-based blood test can accurately detect breast, colorectal, lung, ovarian, pancreatic, gastric or bile duct cancers in patients, researchers report.

The test uses artificial intelligence to identify and interpret "fragments" of DNA in the blood that indicate the presence of cancer, explained researchers led by Dr. Victor Velculescu. He helps direct the Cancer Biology Program at the Johns Hopkins Kimmel Cancer Center in Baltimore.

In the new study, the test -- called DELFI (DNA evaluation of fragments for early interception) -- accurately detected cancer in 73% of cancer patients overall, and only misclassified four out of 215 patients, meaning it had just a 2% error rate.

"DELFI helps identify the presence of cancer by detecting abnormalities in the size and amount of DNA in different regions of the genome based on how it is packaged," said lead author Jillian Phallen, a postdoctoral fellow at the Kimmel Cancer Center.

Still, this is just a proof-of-concept study, the researchers said, and more research is needed before it reaches routine use.

But such "liquid biopsies" are a holy grail of cancer research, potentially making cancer diagnosis easier and faster, and avoiding the need for invasive tissue biopsies.

Many blood-based biopsies are under development, but DELFI relies on a slightly different strategy than most. According to the Hopkins team, the test examines the way DNA is packaged within the cell nucleus. While healthy cells package their DNA in ordered, predictable ways, cancer cells do not -- instead, DNA appears more disordered and random.

This "means that when cancer cells die they release their DNA in a chaotic manner into the bloodstream," Phallen explained in a Hopkins news release. And it's these disorganized bits of DNA that the new test detects.

In the new trial, involving 208 cancer patients, DELFI accurately spotted one of seven cancers between 57% and 99% of the time in blood samples, the team reported May 29 in the journal Nature.

The study group included 54 breast cancer patients, 27 colorectal cancer patients, 12 lung cancer patients, 28 ovarian cancer patients, 34 pancreatic cancer patients, 27 gastric cancer patients and 26 bile duct cancer patients.

Genomic testing from these patients was compared to results from a comparison group of 215 healthy individuals.

As expected, the DNA fragmentation "profiles" of the healthy individuals were more ordered and much less variable than those of the cancer patients.

Besides simply spotting the presence of a cancer, the new blood test was between 61% and 75% accurate in determining the tissue of origin of the tumor, the study authors reported.

And when data from DELFI was added to another mutation-based analysis of "cell-free" DNA, this analysis accurately spotted tumors in 91% of the cancer patients, the investigators found.

This research remains in its early stage. However, "we're encouraged about the potential of DELFI because it looks at a completely independent set of cell-free DNA characteristics from those that have posed difficulties over the years," Velculescu said. "We look forward to working with our collaborators worldwide to make this test available to patients."

The researchers added that because the blood test is easy to administer and analyze in the lab, it could also prove to be a cost-saver.


Copyright © 2019 HealthDay. All rights reserved.


Toward Blood-based Cancer Detection

Jyoti Madhusoodanan
Jul 7, 2015

ISTOCK.COM/NANO While the detection of solid tumors remains routine procedure in cancer diagnostics, modern technologies such as next-generation sequencing have enabled scientists to track cancer beyond its tissues of origin and in greater detail. Many tumors shed stray cells, vesicles called exosomes, and traces of DNA into blood and other body fluids. Recent research has shown that such debris can serve as markers to monitor disease progression&mdashand even help researchers diagnose cancers before symptoms appear.

Tumor DNA, it turns out, can be detected in routinely drawn blood samples. In a study published last month (June 5) in JAMA Oncology, for example, researchers who examined blood samples from more than 4,000 pregnant women&mdashdrawn for the purpose of identifying chromosomal abnormalities in the fetus&mdashidentified three cases of maternal cancers: an ovarian carcinoma, one follicular lymphoma, and a Hodgkin lymphoma. &ldquoIn the majority of these tumors, even low grade ones, we found.

Such “liquid biopsies” are not unique to blood and plasma samples. In other studies, researchers have correlated the risk of bladder cancer recurrence to methylated DNA levels in urine, detected bowel cancer DNA in stool samples, and identified cancer-linked mutations in the saliva of patients with head and neck carcinomas. Previously, such molecular tests were used to monitor advanced disease and metastasis. Now, with increasingly precise tools, small amounts of cancer cells and DNA can be identified in blood even in the earliest stages of disease.

“Stool and urine might detect colorectal or bladder cancer, but blood has the capacity—at least conceptually—to detect all cancers,” said Bert Vogelstein of the Johns Hopkins School of Medicine in Baltimore, Maryland. “Logistically, however, the challenge has been to detect very small amounts of DNA.”

Common evidence

Last year, in a study of 640 patients published in Science Translational Medicine, researchers reported that circulating tumor DNA could be detected in plasma for approximately 40 percent to 70 percent of several types of cancer, including brain, prostate, and ovarian. In advanced colorectal cancer, for example, circulating tumor DNA could be used to pinpoint mutations in the KRAS gene in 87 percent of cases.

Intact cancer cells can also slip into the bloodstream. Early attempts to trap these circulating tumor cells (CTCs) relied on identifying surface antigens or other markers. But CTCs can wear different molecular masks depending on tumor type, stage of disease, and other factors. Earlier this year, however, Mehmet Toner of Harvard Medical School and his colleagues showed in Nature Methods that microfluidic devices could trap these cells using physical methods “independent of tumor-specific markers” from whole blood. “Intact cells have tremendous value,” Toner told The Scientist. “You can look at DNA, RNA, signaling molecules, phosphorylation patterns, epigenetics—it’s much richer [than a single biomarker]. In the long-term, we could culture these cells to test drug susceptibility, really [moving toward] personalized medicine.”

In addition to DNA and whole cells, recent studies suggest that exosomes shed by tumor cells may also serve as surrogate cancer biomarkers. Last month (June 24), a team led by investigators at the University of Texas MD Anderson Cancer Center in Houston described in Nature a serum test for exosomes—which carry DNA, RNA, and proteins—that could be used to successfully distinguish patients with early- and late-stage pancreatic cancer from those with benign pancreatic disease or healthy subjects.

But the rarity of circulating tumor traces—whether bits of DNA, whole CTCs, or expelled vesicles—has thus far made clinical application a challenge. According to Vogelstein, improving the sensitivity and specificity of such molecular tests will be crucial to establishing their clinical utility. In addition to eliminating false positives—test results that conclude “cancer” where there is none—it’s also essential to understand why some tumors can’t be tracked in the blood and other fluids.

“At present, we don’t know whether the limitations are technical or biological,” said Vogelstein. “We’ve found that between 40 and 70 percent of tumors are detectable. But if the remaining early-stage cancers do not ever secrete a single molecule of circulating tumor DNA, then it doesn’t matter how good our technology is.”

Much of the basic biology is also unclear, Tim Forshew of University College London told The Scientist via e-mail. “We still don’t fully know how circulating tumor DNA gets into the bloodstream and how this differs for different types of cancer. We also don’t fully understand what influences how quickly it is cleared from the blood.”

Nonetheless, the possibility of using a simple blood test to diagnose cancer and guide treatment strategies has inspired a flurry of companies that are now racing to create assays.

Early applications

Commercial interest in circulating tumor markers “is huge,” said Forshew, who leads technical development at Inivata, one of several firms that offer circulating tumor DNA-based diagnostic tests. To Forshew’s mind, one of the most important applications of such technologies will be to study the genetics of cancers that cannot be easily biopsied.

Several other companies—including Epic Sciences, Johnson & Johnson’s Janssen Diagnostics, SRI International, and Guardant—currently offer tests for circulating tumor DNA and cells. However, clinical applications of these tests have so far been limited to monitoring metastasis and, to a lesser extent, treatment response.

Scientists conducting clinical studies are working to correlate tumor DNA in the bloodstream with specific disease parameters, such as risk of recurrence after a surgical procedure to remove a tumor. “This is different than predicting prognosis,” said Vogelstein. “It’s actually detecting the presence of occult disease that hasn’t yet shown up in clinical or radiologic grounds so we can implement therapies which could be curative [if begun early enough].”

Working with Vogelstein, Jeanne Tie of the Walter and Eliza Hall Institute of Medical Research in Melbourne, Australia, and her colleagues are using circulating tumor DNA to assess which patients are most likely to benefit from chemotherapy after surgery for stage II bowel cancer. Typically, a large fraction of patients receive adjuvant chemotherapy after surgery. But only 4 percent to 5 percent of patients appear to benefit from it. For the remainder, either surgery proves sufficient or the cancer resurfaces despite chemotherapy. The team’s preliminary results, presented at last year’s American Society of Clinical Oncology meeting, suggest that risk of recurrence closely correlates with circulating tumor DNA levels. The researchers are now planning a larger randomized trial to assess the utility of circulating tumor DNA to inform the administration of chemotherapy. “By using the blood test to guide chemotherapy we not only could improve survival, but also reduce the number of patients receiving [unnecessary] chemotherapy,” said Tie.

Tumor DNA, CTCs, and tumor-derived exosomes are markers of “higher value” than previously used measures such as prostate specific antigen, which are released even by healthy cells, according to Toner. “These new markers offer an amazing opportunity to manage cancer,” he said. “Previously, we were always a step behind the disease and trying to catch up. With these more specific and sensitive tools, we can finally get a step ahead.”


Blood and bone marrow cancer symptoms

Some common blood and bone marrow cancer symptoms include:

  • Fever, chills
  • Persistent fatigue, weakness
  • Loss of appetite, nausea
  • Unexplained weight loss
  • Night sweats
  • Bone/joint pain
  • Abdominal discomfort
  • Headaches
  • Shortness of breath
  • Frequent infections
  • Itchy skin or skin rash
  • Swollen lymph nodes in the neck, underarms or groin

Blood Disorders Affecting Platelets

Blood disorders that affect the platelets include:

Thrombocytopenia : A low number of platelets in the blood numerous conditions cause thrombocytopenia, but most do not result in abnormal bleeding.

Idiopathic thrombocytopenic purpura: A condition causing a persistently low number of platelets in the blood, due to an unknown cause usually, there are no symptoms, yet abnormal bruising, small red spots on the skin (petechiae), or abnormal bleeding can result.

Heparin-induced thrombocytopenia: A low platelet count caused by a reaction against heparin, a blood thinner given to many hospitalized people to prevent blood clots

Thrombotic thrombocytopenic purpura: A rare blood disorder causing small blood clots to form in blood vessels throughout the body platelets are used up in the process, causing a low platelet count.

Essential thrombocytosis (primary thrombocythemia): The body produces too many platelets, due to an unknown cause the platelets do not work properly, resulting in excessive clotting, bleeding, or both.


Treatment discovered for rare blood cancer

University of British Columbia researchers have discovered a potential new treatment for a rare blood cancer that may also point the way to treating other more common diseases.

Paroxysmal nocturnal hemoglobinemia (PNH) is a rare form of cancer characterized by episodic rupture of red blood cells and the

danger of blood clots forming in the vascular system. The condition results in red blood cells becoming vulnerable to attacks by the body's own complement immune system and can lead to complications such as anemia, kidney disease and fatal thromboses.

In a clinical study published today in PLOS ONE, the UBC team, led by Prof. Patrick McGeer, applied aurin tricarboxylic acid (ATA), a non-toxic drug, to blood samples of five patients with PNH who were undergoing standard treatment with antibodies administered through biweekly infusions.

The researchers found the addition of ATA restored blood cell resistance to complement system attacks, while the antibodies alone did not offer full protection.

"Our study suggests that ATA could offer more complete protection as an oral treatment for PNH while eliminating the need for infusions," says Prof. McGeer, professor emeritus in UBC's Department of Psychiatry. "PNH is a disease that may happen to anyone through a chance mutation, and if nature were to design a perfect fix for this mutation, it would be ATA."

McGeer adds that since many diseases are caused or worsened by an overactive complement immune system, the discovery of ATA's effectiveness in this rare disease could have wide-reaching implications for conditions such as Alzheimer's and Parkinson disease, macular degeneration, ALS, multiple sclerosis and rheumatoid arthritis.

The team is now proceeding with further testing and McGeer hopes the treatment may be available in clinics within a year.

PNH and ATA The Paroxysmal nocturnal hemoglobinemia (PNH) mutation leaves cells deficient in two critical proteins -- called protectin and decay accelerating factor -- that in healthy individuals shield the red blood cells from self-attack by the complement system. Aurin tricarboxylic acid (ATA) works by blocking this self-attack and thus compensating for this deficiency.


Monitoring of PTL degradome, the next frontier

PTLs are specialized cells lacking nucleuses. Despite this fact, PTLs are still able to produce proteins since they hold a remaining subset of mRNA from the megakaryocyte progenitor cell and contain all the necessary translation machinery. PTLs transcriptone has been analyzed 3 – 5 . However due to the limited amount of mRNA, the proteomics method 6 offers a better way to analyze the physiological changes in stored PTLs for transfusion.

The term Proteomics represents the gathering of a variety of in evolution technologies aiming protein identification and quantification on a large scale. Contrary to Genomics (mapping genes) Proteomics is more dynamic. Proteins can suffer modifications after translation and interact with other proteins and the showing of proteins in the active form depend the normal physiology changes or environment conditions or the influence of diseases. Therefore, the study of the proteomes provides more information than the study of the genome.

Some of Proteomics methodologies are gel based, such as the two-dimensional gel electrophoresis (2DE) that is in used since the 70′s and more recent differential in-gel electrophoresis (DIGE). Others methods are gel independent methods, like: Shotgun (method of identifying proteins in complex mixtures using a combination of high performance liquid chromatography) multidimensional protein identification technology (MudPIT) isotope-coded affinity tagging (ICAT) and the isotope tags for relative and absolute quantification (ITRAQ). All of them end in mass spectrometry (MS) analysis for protein identification. Protein degradation is expected to occur in stored PTL short within the 5 days, resulting in fragmented peptides. Therefore in this case, the focus should be on a derived branch of proteomics, the degradomics that measures of rise of peptides. This is especially important when we realize that the soon introduction of NAT tests in our Service may cause 1 day deliver delay of the life saving PLTs. The best combination for optimizing the production would be to implement the blood transfusion safety by NAT test together with the straight monitoring of PTLs degradome by a chosen proteomics methodology.

The need to standardize a precise methodology for PLT degradomics measurement became very clear when a variation of results were observed after 3 different methodologies (DIGE, ITRAQ and ICAT) were applied 7 . By DIGE, 93 were identified 355 by ITRAQ and 139 by ICAT. Less than 16 percent of the 503 proteins, however, were identified by not more than at least two proteomic approaches. Only 5 proteins were identified by all approaches. They authors also noticed that membrane protein changes were not reliably detected by 2D gel/DIGE methods. The complexity of these results shows us more research is necessary to apply proteomics as routine in the blood banks worldwide.


What Type and Cross Match Means

Doctors on TV say it all the time: "Nurse, I need you to type and cross the patient."

You probably know that it has something to do with blood, but what does it really mean? First, you ought to know that "type & cross" is short for type and cross match. It refers to tests that blood typically goes through before a transfusion.

Typing

As we discussed, blood types are based on several different kinds of proteins and antibodies that can be present in any individual's blood. In the terminology, type simply refers to the testing process to determine a patient's blood type.

Cross-Matching

Just because the tests all match up and the patients appear to have compatible blood types doesn't mean a transfusion will always work. Crossmatching is a test where a bit of the patient's blood is introduced to a bit of the donor's blood to see how they get along.

Ideally, the blood samples will hit it off like old friends. If they mix well and settle in for a card game and a beer, all is well. On the other hand, if they start throwing punches, It's time to go back to the drawing board (or at least to the blood bank). If incompatible blood is transfused from one person to another, the reactions can be anything from anaphylactic shock to bleeding disorders.

Just to muddy the bloody waters a bit more, a positive test is not a good thing, but a negative test is. In typical medical fashion, the terminology of a positive or negative test is not referring to the preferred outcome, but to the presence or absence of a reaction. So, a positive test means that the blood did, indeed, have a reaction. Usually, that reaction is for the recipient's blood to attack and kill the donor's blood.

A raging battle in one's bloodstream significantly distracts from the blood's ability to actually perform its work.

A negative test, however, means that the two blood samples are truly keen on each other and will work together like old partners.