Han Chau

Hi Anna, I used anti-A and anti-B CSL reagent. Is that what you mean?

I had one lady whose blood group is AB pos was transfused with one unit of A pos and ended up with HTR. Pre transfusion samples: Group: AB (without any discrepancies in the forward and reverse group) Ab screen: Neg DAT: Neg Crossmatch (IAT): Neg Post transfusion samples Pt: showed group AB with mixed field reaction with anti-B demonstrated Ab screen: still Neg DAT: Pos (POLY) and a score of 3 for IgG and of 0.5 for C3b/d Crossmatch (IAT): Pos I performed elution and it was pos for A1 cell and Neg for 11 cell panel. An AB patient with an A subgroup and anti-A1 presented, it's usually naturally occurred IgM (if so, we will have discrepancies in reverse grouping with A1 cell which I don't have with this case). So, possibly it's IgG, and I don't know if anti-A1 IgG (which is clinically significant) can be produced just after the initial transfusion with A1 cell or it carries characteristics of allo-Abs in which an initial sensitization is necessary? On the other hand, anti-A1 Ab is usually not clinically significant. Therefore, the HTR may not be due to anti-A1. Hence, there are 2 causes came up to my mind that the HTR was due to anti-A1 Ab (but it must be IgG to be considered) or the patient produce antibodies to a low incidence Ab which the donor's cells carry. Can I have your opinion about this???? Thanks

Dear Mania Thanks for your useful information and the references. I'll read them. Cheers

Is there Leukemia??? I'm confused since I know PNH patient has triad of hemolysis, thrombosis and bone marrow failure (pancytopenia). Can any one help? :confused:

Sorry for being late. My question is 'Why doesn't enzyme destroy Fy3 and Fy5 but Fya and Fyb?' Cheers

Malcolm, in Aboriginal Australian, when both Lewis and Secreted genes are present, some part of the Le-a still remains instead of transforming all to Le-b, and that's why they are Le (a+b+). Does it belong to the 4th condition that you mentioned or another situation?

Is it Colton blood group antigens?

Malcolm, you're completely right (your memory serves you ) when you said that C4b floated off from the ANTIBODY(IES) after complement was activated (mentioned in the book of Issitt and Anstee). You talked about floating off from ANTIBODY, and I talked about floating off from RBC MEMBRANE , hehe Also from the book, I feel like many authors have tried to figure out why Rh blood group Ab doesn't fix complement and the question is still opened. However, the book is from 1999, I'm not sure if there is any new research done after that. However, after reading the book, personally, the explanation of 2 IgG are too far for complement to bind to is still....not satisfying me (although it's clear that RhD antigen widely spread on RBC membrane) since the IgM of Rh blood group system doesn't activate complement either. So, personally there is possibly some thing on the Rh blood group Ag or Ab which prevents the complement from being activated. If it's the problem of the distance, IgM can activate irrespective of that, indeed it's not. However, I'm just wondering since it may be hard to find the final answer. And...about the hypothesis you mentioned (it's Rosenfield's explanation) , the book has one part that mentions about it. However, at the end of the paragraph, the authors said that it's possibly not because Rh antigens have seemed to be 'embedded in or located very closed to RBC membrane', so it's less likely that C4 decays before it reaches the membrane. However, the authors didn't completely deny the hypothesis (I think) since they mentioned it somewhere in another chapter in the book as many mentioned explanations for why Rh Ab doesn't fix complement. If we both are not satisfied with the information from the book, let's do some more search about recent findings about it to ensure that the problem is really pending there .

TRALI caused by anti-HLA in donor's plasma, so anti-HLA is the answer, isn't it? My question is: What may be other cause of TRALI?

Thanks Malcolm for your question since that the thing I've never thought about when studying about Rhesus blood group system :tongue: However, from brainstorm here is my possible explanation: R2R2 (I'm talking about exceptional -D- later) has the largest number of D antigen site on RBC (approx 16,000 to 33,000) compared to other Rhesus phenotypes but it still can't activate complement while Jk with lower number of antigen sites on RBC (approx 14,000) but CAN activate complement due to the distribution and arrangement of antigen. Jk antigens appears as cluster, not randomly appearing as RhD. Therefore, I thought the way the Ags go together on the RBC surface is more important than the number of Ag site (in some aspect) However, with -D-, it has the largest number of antigen site (110,000 - 202,000) but it can't either (as you said). In -D-, there is an increase of D expression which makes 2 IgG very close for anti-IgG to crosslink and cause agglutination but possibly because of its random distribution, it is still too far for C1q to cross link. I think in this case it relates to the distance between 2 IgG and the size of C1q. This is just my thought without references except the given numbers . However, I'll do a search on that after my exam time is finished And for the theory you mentioned, I don't think it's reasonable. From what I was taught, complement bind very strongly to RBC by covalent bond once it's activated (and that's why in CAD, patient's RBC have DAT positive for complement only). The only complement component that can flow off the RBC is C5b, and C5b is formed once complement cascade was already activated (this means the related RBC was already attacked by complement). In Rhesus, complement hasn't been activated, how is C5b formed to flow off the RBC? That's why I thought it's not the answer. However, my knowledge is still limited, and possibly my explanation here is not....correct . I will do a search on that after my exam. At the meantime, if any of you have the answer, please let me know so that I can learn from that. Thanks And once again, thank Malcolm for you question Cheers Han

I agree with you. Two RhD antigens on RBC surface are not close enough to be linked by C1q, so complement can't be activated. Cheers Han

Dear Donna Thanks for your reply. If I really can remind you something with some of my post, it will be my pleasure. I'll do my best to learn and achieve more from this forum, just hope, hehehe Cheers Han

Hi Adiescast and Steven Firstly, thank you for your reply and encouragement. This forum is really helpful, especially to an unexperienced person like me . However, in posting answer, with limited knowledge of a student, I probably won't have a proper or correct one. Hopefully, it is sympathized. Thanks Cheers Han

Hi Jessi and Adiescast (Jessi, hopefully I understand your question correctly now For anti-IgG, the antibody will recognize the Fc (as I mentioned, it is composed of constant domains heavy chains) of IgG rather than Fab. Fab's function is to recognize epitope on antigen (rather than to be recognized by anti-Ig). Moreover, every specific clone of antibodies is determined by the Fab. It means, different clone of Abs will have different Fab 'configuration'. In fact, we don't have specific anti-IgG which is just used to detect a particular clone of IgG. Once it's called anti-IgG, it will detect any IgG irrespective of its clone. This explains why anti-IgG directs against Fc because Fc is similar for every IgG molecule. Moreover, Fab is different while Fc is quite similar between individuals in the population. Therefore, the anti-IgG is produced against the Fc part of IgG. For example, rabbit IgG can be used as anti-human globulin because rabbit IgG recognize human Fc as foreign. Moreover, for this reason, the anti-IgG reagent can be applied for any IgG from every patient and there is no difference between individuals. I don't know if my answer hit the point. Just hope Cheers Han

I'm not quite sure what do you mean by 'use'. However, I'm doing my best. Every immunoglobulin (Ig) has heavy chains and light chains. As Malcolm said, the light chains can be either kappa or lambda. Heavy chains can be gamma, mu, alpha, epsilon or delta which determine whether the Ig will be IgG, IgM, IgE, IgA or IgD respectively. However, I think in blood transfusion, it's more important to mention about Fc (Fragment crystalline) and Fab (Fragment antigen binding) parts of Ig rather than light chains and heavy chains. Fab which consists of variable and constant domains of both light chains and heavy chains. A hypervariable region on Fab is responsible for recognizing antigen (exactly it's epitope on antigen). Fc is composed of just constant domains of heavy chains. Fc is the part which is recognized by phagocytes (by Fc-receptor on the cells). Therefore, the target cell which carry the corresponding antigen will be destroyed by phagocytes. Moreover, on Fc portion of IgG and IgM, there are receptors for complement to bind to. This explains why IgG and IgM can activate complement cascade whist other classes of Ig cannot. Cheers Han

Hi Malcolm Thanks for your reply. I'll do my best Regards Han

Hi I'm a student doing Blood transfusion course in Australia. I found that this forum is very helpful since I can learn a lot from your posts. Regards Han