Why is Anti-A,B reagent used to test O cells?

Anti-A,B tends to be more avid than does either anti-A or anti-B, or a mixture of the two, even in these days of monoclonal antibodies. Thus, you are more likely to detect A and B subgroups, such as a very weak Ax, and this is important if an anti-A1 is present, so that the reverse group using just A1 and B cells, looks like a group O. This is probably more important on the donor side of things, than on the patient side of things, although Martin Olsson tells me that a weak Ax, transfused to a group O patient, tends to only raise the titre of the recipient's anti-A, rather than cause an acute HTR.

I wouldn't do this as an experiment!!!!!!

Thank you Malcolm, that was fast and I needed the reply before noon !!! (Its 10:30am now). Am I lucky to have a friend like you, and this forum to turn to, or what?

That's a pleasure.

Incidentally, I think the reason that anti-A,B, or, at least, human-derived polyclonal anti-A,B, reacts more avidly with weak ABO subgroups than does either anti-A or anti-B from a similar source, is because it tends to have a higher level of IgG ABO antibody present, and this will, of course, cause agglutination at quite low temperatures. One only has to see the agglutination in the EDTA sample from a baby suffering from ABO HDN that has been kept in a fridge to see this.

We have been practicing this since ages and I never asked why :disbelief...I did look it up because I was ashamed to ask here such a basic question but didn't find anything......

Merci

I wouldn't do this as an experiment!!!!!!

Ah, come on...where's your sense of adventure, Malcolm?

Malcolm,

Can you explane this a little it more. (the higher level of IgG, higher that IgM or higher than other samples?), and the fact of the IgG reactive at lower temp. Also the line about EDTA sampel in the fridge is new for me.

Malcolm,

Can you explane this a little it more. (the higher level of IgG, higher that IgM or higher than other samples?), and the fact of the IgG reactive at lower temp. Also the line about EDTA sampel in the fridge is new for me.

I'll certainly have a go Peter.

You will be aware that most cases of ABO HDN tend to involve group A or group B babies born to group O mothers (although, of course, this is by no means a "universal truth"). In addition, haemovigilence schemes, such as SHOT in the UK, show that the number of ABO acute haemolytic transfusion fatalities tend to involve group A blood being given to group O recipients (although, again, this is by no means a "universal truth").

Back in the days of human-derived ABO grouping reagents, used when I was young (which shows just how far back we are talking!), part of my duties at the Blood Group Reference Laboratory was to titrate the plasma of donors against A and B red cells to see which units would be suitable for reagent use. In almost all cases, the anti-A and anti-B titre (or, to put it another way, the anti-A,B titre) of group O donors were more avid and gave a higher titre than the anti-A from group B donors and the anti-B from group A donors. In addition, many of the samples from group O donors showed the ability to be haemolytic (this was in the days of clotted blood, before we collected the side tubes into EDTA), and this was comparativelt unusual for reagents derived from group A or group B donors.

We are now seeing the same thing in group O renal patients prior to work-up before iABO renal transplants. Here, we are titrating the plasma for IgM ABO antibodies, and for IgG ABO antibodies, following treatment of the plasma with DTT. In almost every case, the IgG titre is higher than the IgM titre, prior to IVIG being given.

From this, it will be seen that the ABO antibodies from group O individuals tend to be more avid and of a higher titre than their group A and group B counterparts.

ABO HDN is caused, by definition, by maternal ABO IgG antibodies (otherwise, the antibody would not pass through the placenta). It will, therefore, react at body temperature, otherwise the baby would not be affected (unless, of course, the sensitisation takes place in the body extremities, such as the fingers - and there is no evidence for this). However, if you place an EDTA sample of blood from a baby suffering from ABO HDN into a fridge at 2 to 6oC for some time, when you take it out again, you will sometimes see frank agglutination of the red cells, and this is not caused by either maternal (or the baby's) anti-I, anti-HI, anti-i or anti-Hi. It is the maternal IgG ABO antibody causing the agglutination. In other words, the ABO IgG antibody has the ability to agglutinate red cells without potentiators, and over a wide thermal range (don't forget that the Donath-Landsteiner anti-P is IgG, but also sensitises in the cold - so this is not unique).

I believe that it is for all these reasons that human-derived polyclonal anti-A,B is often able to detect the Ax sub-type, whilst human-derived polyclonal anti-A is not.

I hope that helps a bit, but if not, come back to me, and I'll give it another go!

:bow::bow::whew::whew:

Thank you for the explanation Malcolm and for the time you took writing it!!

Thanks Malcolm,

Your explanation is realy clear. We also see a lot of patients with an hemolytic anti A or B in patients with a child suffering from HDN (AO or BO).

IgG antibodies reactive at lower temp is also seen with monoclonal antibodies against M, N, and A or B. Some reagents are IgG but because of the high antigen expression they will give stong reactions at RT without additives.

Can the fact that A to O wrong transfusions is the most common form in the SHOT report also be due to the fact that these bloodgroups are the most common? The amout of A units that is send out of the lab is much higer than the amount of B units.

Peter

Thanks Malcolm,

Can the fact that A to O wrong transfusions is the most common form in the SHOT report also be due to the fact that these bloodgroups are the most common? The amout of A units that is send out of the lab is much higer than the amount of B units.

Peter

It is undoubtedly true that more units of group A are given to group O patients in error than group B or AB, but the figures show that there is a higher death rate associated with A to O transfusions than there is with, for example, A to B, where there may be major morbidity, but not the same rate of mortality.

Correct me if I am incorrect, Malcolm, but isn't it true that a Group O individual's Anti-A tends to be stronger than his/her Anti-B?

Donna

No, you are absolutely correct Donna.

This is usually, although, once again, not universally, the case, particularly amongst people of white ethnicity.

It is less true within people of black ethnicity, because of the enhanced B antigen strength often present. Therefore, there tends to be "more sensitisation" from a group B baby to a group O mum, and this is why ABO HDN due to anti-B is more common in the black population than the white.

Edited September 14, 201113 yr by Malcolm Needs
Continued inability to spell.

No, you are absolutely correct Donna.

This is usually, although, once again, not universally, the case, particularly amongst people of white ethnicity.

It is less true within people of black ethnicity, because of the enhanced B antigen strength often present. Therefore, there tends to be "more sensitisation" from a group B baby to a group O mum, and this is why ABO HDN due to anti-B is more common in the black population than the white.

I showed this thread to a student of mine because he just asked me these questions. His follow up question was whether Group O individuals of black ethnicity have a higher titer of Anti-B compared to their Anti-A naturally or is it just due to the extra B sensitization?

I showed this thread to a student of mine because he just asked me these questions. His follow up question was whether Group O individuals of black ethnicity have a higher titer of Anti-B compared to their Anti-A naturally or is it just due to the extra B sensitization?

The simple, but once again, not universal answer is yes.

Thanks, Malcolm. I told him you would reply before we left for the day!

I have heard that the Anti-A,B used to be a different formulation, which was a little stronger as Malcolm stated above. But when we switched manufacturers, we were told that their A,B was just Anti-A and Anti-B mixed together with no dye in it. That's when we dropped it and just started using Anti-A and Anti-B for all unit retypes.

I have heard that the Anti-A,B used to be a different formulation, which was a little stronger as Malcolm stated above. But when we switched manufacturers, we were told that their A,B was just Anti-A and Anti-B mixed together with no dye in it. That's when we dropped it and just started using Anti-A and Anti-B for all unit retypes.

You can check this with the clone names, somethimes they are on the label but they must be in the instruction. Most anti A,B have special clones (directed against A, sometimes with the adition of a anti A or anti B clone.

Two questions: It was speculated that anti-A,B reacts with a determinant common to both N-acetyl-D-galactosamine and D-galactose, the sugars confering A and B specificity, which differ only on the substitutions at the 2nd carbon position. Has this been verified?

I had also heard a while back that monoclonal anti-A,B was just a mix of anti-A and anti-B. But as Peter outlines above, our Immucor anti-A,B is not just a mix but also has a clone producing anti-A,B as well. My question to users is why bother typing patients with the reagent? It's fun, and serologically accurate, to find Ax patients, but they are rare, and we happily mistype them and other subgroups with anti-A1 as group O, give them O blood and, none the wiser, all goes well. We use the reagent to verify group O donor units simply because it's half the price of using both anti-A and anti-B.