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Malcolm Needs

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Everything posted by Malcolm Needs

  1. These are, for want of a better way of putting it, antigens that are expressed on IgG molecules. Gm stands for Gamma marker and Km stands for Kappa marker. An individual will have their own Gm and Km types, and all of their antibody molecules will express these types. However, other individuals will (probably) express different Gm and Km types and, of course, anti-D immunoglobulin is made from a pool of human-derived anti-D. Therefore, if the anti-D in the circulation has multiple Gm and Km types, it is almost certainly derived from anti-D immunoglobulin. On the other hand, if the anti-D has the same type as the patient, it is probably an allo-anti-D. That having been said, however, this has never been proven (as far as I know), and, even if there is a "soup" of Gm and Km types in the circulation, this does NOT disprove the presence of a weak allo-anti-D. This is why I put this forward as a possible way of serological typing, but I also did say that it is not 100% reliable.
  2. Agree entirely David (apart from the fact that antigens and cells cannot be homozygous, heterozygus or hemizygous, only genes can be termed as such). In the UK, of course, we do an enzyme panel in most cases, but I do agree that, in reality, r'r' and r"r" red cells are, in reality, only available to Reference Laboratories, and only then used sparingly (not least because antibodies that are that weak are rarely, if ever, clinically significant, either for HTR's or HDFN). My point, however, was that, from a serological point-of-view, unless you can perform Gm and Km typing of the antibodies, you cannot tell the difference between a passive anti-D and a weak allo-anti-D (and even that is not 100% reliable), you HAVE to rely on the patient's history as to whether or not she has been given prophylactic anti-D immunoglobulin, and whether or not there was any evidence of allo-anti-D in her circulation before she was given any prophylactic anti-D immunoglobulin.
  3. It does bowerj1, except you are doing yourself, and the rest of us down. Peds never did "do" the babies of O moms. Most of them wouldn't have a clue how to "do" the babies of O moms. It is people like you, me and many thousands of scientists within the Blood Bank who "do" the babies of O moms.
  4. Yes David, I realise it is usually 1+ in gel, but so is an allo-anti-D that is just forming. That is the problem.
  5. Sadly, it is not that easy. It is incredibly rare for an anti-D to show dosage, however, there can be noticeable differences in the strength of expression of the D antigen, even between individuals with the same Rh phenotype and, indeed, genotype.
  6. Certainly is. If you ever get to the bottom of it - and sometimes you just can't - let us know please.
  7. The other thing could be that the clones used in the anti-D have changed, and they no longer detect a particular mutant type.
  8. Sounds like either impersonation (had you seen the patient yourself before?) or rare case, as you suggest above.
  9. Tomorrow is Thursday in the UK. I have the enormous pleasure of taking my wife out for her to do some shopping. Therefore, in case I forget in the fever of excitement I will be feeling tomorrow (ugh!), I would like to wish all of my friends who are either in, or are from the United States of America a very Happy Thanksgiving.
  10. I agree with Veejay. The reaction is with the A antigen, not a fictitious antigen named A2, and so the antibody is anti-A, not anti-A2. This A antigen is also expressed on A3, Ax, Am and other group A subgroups, not just on A2 red cells, but, importantly, is also expressed on A1 red cells, as is the A1 antigen. For details, see the attached PowerPoint. What is the difference between A1 and A2.pptx
  11. Well, as a matter of correct nomenclature, I wouldn't put it like that. Homozygous, heterozygous and hemizygous are terms that should be reserved for genes, and red cells do not contain a nucleus, let alone genes. However, in terms of antigen expression, I would say homozygous, heterozygous or hemizygous expression, where possible (there are some antigens that show no "dosage" in terms of expression) than can be non-reactive by ANY serological technology. The Sd(a) antigen, which used to be within the 901 Series of High Prevalence Antigens has just become a blood group system (the SID Blood Group System), but approximately 91% of individuals are serologically Sd(a+), but a further 5% are Sd(a+) when their urine is tested, and only 4% are truly Sd(a-), so this kind of thing must be remembered when you are talking about different technologies and techniques. It's not easy!
  12. First I've heard of this and, on the face of it, I disagree entirely.
  13. I would tend to agree with George Garratty (who wouldn't!?), but, having seen many cases of out of ABO group transfusions of platelets, FFP and cryoprecipitate, and having studied, as much as possible, there have been very few cases where there have been any clinical problems confined to cases involving very small babies given ABO mismatched platelets, FFP and/or cryoprecipitate, but never children of small stature or adults, and, in these cases, there does not seem to have been any problems ABO typing these patients after the transfusions. What may be of interest is, I think, a unique report of a case where a patient, with no atypical alloantibodies, who was given two units of blood, one of which was K+, and one of which contained a high titre anti-K, and these two units reacted in the patient's circulation (see attached scan). Zettner and Bove.docx
  14. I am sorry noelrbrown, but I don't think your definition of a Weak D would pass muster. There are now 170 different Weak D types that are officially recognised, and by no means would all of these react as you suggest. I still maintain that it is virtually impossible to come up with a true positive and negative quality control, even leaving out both Partial D types AND those types that are not yet designated as either Weak or Partial (of which there are very many). Any quality control that does not take this into account is no more than a sop (and by that, I don't mean a Standard Operating Procedure, but a mere gesture) to show that an effort has been made, but that gesture is actually doing nothing but salving a conscience.
  15. The answer to your first question is no. The answer to your second question is that there is no such thing as anti-A2, either natural or immune.
  16. That is very sad. The final decision should depend upon a clinical discussion between the pediatricians, who know about babies, and the pathologists, who know about the value of the test results. No one discipline knows everything about everything.
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