What do you think?

[Liz]

By

Mark H. Yazer, Martin L. Olsson, and Monica M. Palcic

"The cis-AB phenotype can raise questions about an apparently paradoxical inheritance of the ABO blood group, such as the birth of an O child from an AB mother. These subtype ABO alleles confer the ability to create both A and B antigens with a single enzyme. A variety of different cis-AB enzymes have been reported and many feature an interchange of amino acids between the normal A enzyme sequence and its B counterpart, rendering the mutant enzyme capable of creating both antigens. The resulting red blood cells do not usually express A or B antigen at the same level that would be expected on common group A 1 or B red blood cells, and the results of investigations into the kinetics of the cis-AB enzyme more clearly predict the extent of antigen expression. By correctly identifying the cis-AB phenotype, the blood bank can be of assistance to a clinician faced with a patient with what appears be a genetically impossible ABO blood group.

So Malcolm, genetically they may have found A1 and this A can create both enzymes so you were able to adsorb and elute anti-B.

What do you think?

You seemed so disappointed.

[Malcolm Needs ☆]

Thanks for that Liz.

I was aware of this, but I am also aware that ABO genotyping is fraught with danger.

There was a case not so long ago when a renal patient was typed as A by genotyping (serological ABO typing was NOT performed). When they transplanted a group A kidney, there was an episode of hyper-rejection. It turned out that, although the patient was genotypically A (I can't remember whether they were AA or AO), they were phenotypically group O, with a strong anti-A+B.

I'll try to dig out the paper. I think Jill Storrey was one of the authors, but I'm not sure (so apologies to Jill if I am wrong).

In our case, the genotype was A (again, I can't remember whether it was AA or AO).

That was a really useful post.

Thanks.

:D:D:D:D

[marilynm]

Is she Oriental? If so, maybe ABsub? Other possibility is group A with missing isoagglutinin.

So, are you going to get ABO genotyping done?

Marilynm

PS On another note, are you going to aabb in Baltimore? I am cochairing a RAP session with John Moulds on tube, gel and solid phase and am encouraging everyone to think about presenting or attending.

[Malcolm Needs ☆]

Is she Oriental? If so, maybe ABsub? Other possibility is group A with missing isoagglutinin.

So, are you going to get ABO genotyping done?

Marilynm

PS On another note, are you going to aabb in Baltimore? I am cochairing a RAP session with John Moulds on tube, gel and solid phase and am encouraging everyone to think about presenting or attending.

Hi Marilyn,

No, this lady was British through and through, but, as you may have read in an earlier post, we have now lost touch with her, not least because she was scared stiff of hospitals, and we didn't want to worry her any further (well, truth be known, we did, but we thought better of it after discussion with our Consultant!!!!!!!!!!).

As to Baltimore, the answer is unfortunately not. I have never been to an AABB Meeting, and would love to goto one, but the only way I can get there (with payment from the NHS Blood and Transplant) is to be the main author of a poster, or by giving a lecture.

I have half an idea about a poster for the following AABB, but, as for lecturing, nobody has ever asked, and I'm not sure that I am expert enough on any particular subject to deserve to be asked in the first place.

THEN, I HAVE TO PERSUADE MY WIFE TO LET ME GO!!!!!!!!!!!!!!!!!

:o:o:o:o:o:o:o

[Eagle Eye]

when is this session?

[jeanne.wall]

It is (9235-TC) Research and Progress (RAP) Session: Family Feud: Differences in Opinions on Tube, Gel, Glass Beads and Solid Phase Application on Sunday, October 10th, 6:00 PM - 7:30 PM

[Eagle Eye]

Thank you.

[cbaldwin]

I am a student and am reviewing this very interesting case because I am trying to understand ABO discrepancies that are cause by subgroups of A and B. After reading this thread and reviewing page 120 of Harmening's Modern Blood Banking, I am wondering how it was determined that this patient had B_el and not B_m .

And, my next question, is it true that usually it is enough to know that an A or B subgroup is causing the discrepancy, and the actual identification of the subgroup is interesting but not necessary?

Besides Harmening's book, what is a good source for information on subgroups? The Antigen Fact Book?

Thank you!

[Malcolm Needs ☆]

I am a student and am reviewing this very interesting case because I am trying to understand ABO discrepancies that are cause by subgroups of A and B. After reading this thread and reviewing page 120 of Harmening's Modern Blood Banking, I am wondering how it was determined that this patient had B_el and not B_m .

And, my next question, is it true that usually it is enough to know that an A or B subgroup is causing the discrepancy, and the actual identification of the subgroup is interesting but not necessary?

Besides Harmening's book, what is a good source for information on subgroups? The Antigen Fact Book?

Thank you!

Hi Catherine,

The reason I came down on the side of ABel, rather than ABm, was because of the fact that we got absolutely zero aggluination with anti-B, but were easily able to elute anti-B from the red cells following adsorption. As the eluate gave such strong reactions, it is likely that the anti-B that had been adsorbed onto the B antigen was quite loosely bound.

That having been said, it is very much a subjective, rather than objective answer on my part.

Personally speaking, I think that you are correct in saying, once you know it is a weak A or B subgroup, does it actually matter what is the exact subgroup. In 1975, Race and Sanger wrote in their book Blood Groups in Man,

"We sometimes wonder whether since 1911, or say 1925 to take in Bernstein, the only contribution of the first magnitude to the {ABO} system are to be found in the biochemical work on the ABH substances and in the work on the 'Bombay' phenotype; and in the recognition on the cis AB phenomenono and perhaps, on a more practical level, the finding of specific agglutinins in extracts of seeds and snails."

This, of course, was before the invention of monoclonal antibodies and molecular techniques.

Somewhere else in their book (and I can't find the exact quote at present) they say that they hope Aend and Afinn are exactly what they say! The end of finding ever weaker subgroups.

Certainly, the specificity and strength of monoclonal antibodies has largely rendered the old classification of weak A and B subgroups, all of which were made using polyspecific reagents, whether direct aggluination of inhibition with saliva, redundant. In addition, it has been shown that the same apparent serological A and B subtype can be as a result of a multitude of molecular mutations, meaning that the prediction of an ABO group from molecular studies is fraught with danger.

I am no longer sure, therefore, that the teaching, and more importantly, the examination on the knowledge of the very weak A and B subgroups should any longer be part of the curriculum for exams, and I do not think that lecturers have yet taken this into consideration (and they should). Because they have not, however, I'm afraid that you will keep having to adsorb and reproduce this knowledge Catherine.

Geoff Daniels' book, Human Blood Groups is absolutely excellent on the subject of ABO subgroups. His third edition is due out next year, but, be warned, he is now working on the final chapter to be written, and he tells me it is enormous, and,..........guess what blood group system it is on. Yep, ABO!!!!

:fear::fear: