Rh autoantibodies

[Jesmond 12]

Hi everyone

We had a case of a 30 year old female with AIHA and a Hb of 5g/dl. Her EDTA plasma reacted with all screening cells (CAT-IAT) and Identification cells (CAT- IAT and Enzyme). The reactions were all of the same strength; 3+ in the IAT and 4 + in enzyme. The auto control in IAT was also positive. We repeated the screen using the tube technique and monospecific coombs IgG. The screen was positive with all the cells. The DAT with polyspecific AHG was strong positive. Reswults with monospecific AHG were as follows (anti-IgG strong pos; anti C3d weak Pos). The patient was never transfused, blood group A RhD Positive, K negative, and ccDEe phenotype. We performed an warm allo adsorption using R1R1, R2R2 and rr cells. the following results were obtained on the adsorbed plasma. R2R2 - no antibodies detected; R1R1 - anti-E identified; rr - both anti-D and anti-E identified. I have never encountered auto anti-D and auto anti-E together. I was wondering if anyone has had a similar case or could share some ideas and information:o

Thanks

Jesmond

[Malcolm Needs ★ 4,773]

An interesting case Jesmond.

Auto-antibodies, in such cases, often mimic Rh specificities, but you will find that, if you carry on performing alloadsorptions (until you become bored stiff!!!!!!) that such antibodies as your auto-anti-E and auto-anti-D will be totally adsorbed out with cells that are, respectively, E- and D-. In other words, the apparent auto-anti-E and auto-anti-D can be adsorbed out with antigen negative red cells, showing that the original specificity was a mimicking specificity.

The true specificity is often, but by no means always, something like auto-anti-Rh17 or auto-anti-Rh18.

We had a similar case last week, where the patient was an R2r, with a panagglutinin. Following adsorption, there was an apparent auto-anti-e and an apparent allo-anti-C. However, we continued with the adsorption studies and, eventually, we were able to adsorb out the apparent allo-anti-C with both R2R2 and rr red cells, and the apparent auto-anti-e with the R2R2 red cells, suggesting that the auto-antibody was reacting preferentially with C+ (and e+) red cells.

We decided to "play it safe", however, and issued an antibody record card to the patient quoting the "allo" anti-C, with the advice that C+ units should not be transfused to the patient!

[Jesmond 12]

Hi Malcolm

Thank you for your reply. I only performed 6 allo adsorptions, until the DAT on the adsorbing cells came negative. In this case our consultant too wanted to play safe and we issued 4 units A rr. Malta is a small country and we do not see much of these cases..... I think most of you would say Lucky them..... but I still enjoy working on them.

Once again thanks for your information

regards

Jesmond

[sshel55 14]

How many allo adsorptions do you perform before becoming concerned about diluting an allo-antibody to the point of non-reactivity? 

[Malcolm Needs ★ 4,773]

We would alloadsorb a maximum of 8 cycles, but this is more to do with the fact that, if the auto-antibody has not be fully adsorbed out by then, it is not going to be fully adosrbed out with more cycles, than worrying about diluting out an alloantibody.