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Hi! Should it rather be "ex-vivo" in the question? I got confused...

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There was no recording in these "good old days" unfortunately. I had the chance to spend a few days with Sue some weeks ago (we were lecturing at the same event) and I should say that on the top of what Malcolm wrote which is very true, she is such a wonderful person, as Malcolm is!

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The most likely answer has been given above: newly formed autologous red cells have a lower gravity than transfused cells and will concentrate at the top of the re cell pellet whereas transfused cells will seat at the bottom. I hereby attach a paper describing that phenomenon. I hope Grifols will thank you for giving them the answer :-) 20230301142735376.pdf20230301142735376.pdf

Wanted to say... anti-human IgG of course and not human anti-IgG..... sorry for that. I use the opportunity to add that AHG card should have a slightly green colored gel (based on similar products available in Europe) whereas the neutral-saline should be transparent.

Hi Clarest, I am not familiar with the MTS product line, but to me it says that enzyme treated cells can be used in AHG card (the human anti-IgG is already in the gel card of course) though you may experience some non specific reactions plus a higher detection rate of unclinically significant antibodies (specific but unwanted...). This uses (enzyme + AHG), as mentionned above, should be well understood/assessed/validated/targeted => you will as well enhance the reactivities for other clinically significant antibodies such as anti-Jka which is the purpose. Then, they rather recommend to use these enzyme treated cells in their "neutral-saline" cards (called buffered gel), which does not contain AHG. It is propably a way to prevent you to complain if you get an increase of positive reactions to be further investigated whereas this is mostly due to unclinically significant antibodies. Enzyme reactive antibodies (e.g. anti-Rh) are "expected" (why antibodies do no read IH books...) to agglutinate in neutral-saline cards as ABO agglutinins do, without AHG. Having said that, anti-Jka are better detected in coombs + enzyme ....

@Bet'naSBB yep the patient was K neg.

I do not know if Malcolm's case was published (I did not find it?) but this kind of auto anti-K mimicking an allo antibody is well described in this paper issued back in 1982 Autoanti-K antibody mimicking an alloantibody, Transfusion Jul-Aug 1982;22(4):329-32, E. Viggiano et al. This anti-K was adsorbed onto and eluted from both K pos. and K neg. cells.

This phenomenon is also described with the monoclonal antibody therapy anti-CD47 (Hu5F9-G4) where red cells are so heavily loaded with IgG that it creates steric hindrance. Basically, antibodies bound to the red cells hinder the binding sites of the anti-human globulin leading from very weak to negative DAT. Anti-CD47 can be eluted off the red cells and it gives very strong reaction in IAT. Of note: it is not the same mechanism involved with the anti-CD38 (another monoclonal antibody therapy often called DARA) where here the DAT can be negative too because of down-regulation of CD38 expression onto the red cell membrane.

In this paper from 1985, "The Lui elution technique A simple and efficient method for eluting ABO antibodies c. s. FENG, K. c. KIRKLEY, c. A. EICHER, AND D. s. DE JONGH, TRANSFUSION 1985; 25:433-434.", the authors thank A. Lui. MT(ASCP)SBB, who introduced this technique to them. Therefore, I believe Lui is the name of the MT who invented this elution method.

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There are a very few cases of severe HDFN caused by anti-Kpa (see references below). I believe that in many guidelines (to be confirmed though), antibodies to Kell blood group antigen are handled, by extrapolation, the same way as anti-K due to the very few examples reported in the literature. Costamagna L, Barbarini M, Viarengo GL, Pagani A, Isernia D, Salvaneschi L. A case of hemolytic disease of the newborn due to anti-Kpa. Immunohematology. 1997;13(2):61-2. PMID: 15387785. Tuson M, Hue-Roye K, Koval K, Imlay S, Desai R, Garg G, Kazem E, Stockman D, Hamilton J, Reid ME. Possible suppression of fetal erythropoiesis by the Kell blood group antibody anti-Kp(a). Immunohematology. 2011;27(2):58-60. PMID: 22356520. Smoleniec J, Anderson N, Poole G. Hydrops fetalis caused by a blood group antibody usually undetected in routine screening. Arch Dis Child Fetal Neonatal Ed. 1994 Nov;71(3):F216-7. doi: 10.1136/fn.71.3.f216. PMID: 7820722; PMCID: PMC1061131.

When you say asymptomatic, does it mean she is not anemic? What about the reticulocyte count, bilirubin, LDH, haptoglobin? May be the mother has a compensated hemolytic anemia?

Here is an interesting paper showing that antibodies to red cell/platelet... may be transmitted via breast milk indeed, causing prolonged HDFN. Milk contains mostly IgA but IgM and IgG may be present of course and IgGs can cross the different barriers up to blood circulation (not on the same model - not actively - as the placenta though). The surprizing part here is the mother and baby are group A, A antigen is ubiquitous so the anti-A titer in breast milk should high enough to interfer with reverse group despite the adsorption of anti-A on various tissues. https://pubmed.ncbi.nlm.nih.gov/30720868/

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