What D might this be?

[Mabel Adams]

We have a prenatal patient that types variously at IS with anti-D, either negative to about 1+ depending on the reagent. She reacts at AHG from W+(us with quotient anti-D blend and Gammaclone anti-D blend) to 3+ (ARC with Gammaclone and Biotest). ARC says they used the Alba partial D kit and she reacted with all the reagents about 2+. She has made anti-D, G & probably C. A few years ago she was in another city and that lab said they did RFLP testing on her and proved that she was D positive. She had anti-D & C at that time too. She was transfused once somewhere, we were told, but I don't know whether she got D+ or D- blood. So what sort of partial D is she? Weak D 1 or 2? Some sort of DIII? Do these usually make anti-D?

[Malcolm Needs ☆]

Hi Mabel,

There are VERY rare examples of individuals who are Weak D type 1 and 2 who have made anti-D, but this does not sound like one of these.

Anti-D made by an individual who is Partial DIII is common, but it doesn't sound like one of these either, as the individual's red cells tend to react strongly with all examples of reagent anti-D.

I wonder whether or not the entire RHD gene was probed by the RFLP, or whether they just probed certain exons. It is cheaper and much more common to probe 3 exons within the RHD gene than to probe the full RHD gene, but, if the mutation is not within the three exons, it may be missed.

Without knowing this, it is not possible to say whether or not she has the "wild type" RHD gene (unlikely, unless the anti-D is an auto-antibody - which, in this case, does not seem likely), or whether she has a mutation or mutations present, and therefore, unless we know more, it is not possible to say what kind of D antigen she is expressing.

That is correct, is it not Peter?????????????????

[Rh-fan]

Yes and no

In samples with weak D type 1 an auto anti D is rare, but in a type 2 it is more common. (type 1 is stronger and mostly expressed with C, while type 2 is weaker and expresses an E) Because of the weaker expression of type 2 the pressence of auto anti D is a little bit more common (not normal, but shown more than in type 1).

The weak reaction you mention do fit with an antigen with a weak expression, but tells you nothing about the fact if the antigen is normal or missing epitopes. I Assume that patient expresses the E and no C antigen. The strengthe you mention (weak at IS and 3+) is what we see with type 2 weak D (but still no proof).

Partiela DIII variants have normal a stronger expression of the RhD antigen that is the reason that it is not matching your findings, but there is no monoclonal anti D that is not reactive with DIII variants, we normaly only find these patients if they have made anti D (confirmation is done by the use of a polyclonal anti D (made by an another pateint with an RhDIII)). So it is possible that the ALBA kit is total reactive.

Only 3 exons is deffinatly not enough you have to do more on DNA.

The ALBA kit is recognising the most common (although they are all rare) RhD variant antigens, in the fact that one of the monoclonals is not reactive. The conclusion on the name givving of the variant is not always correct but it is very good in making a difference between a variant and a normal (weak) RhD antigen.

On the serological findings I think you are dealing a weak D type 2 with an auto anti D, auto anti G and maybe allo anti C. My advice give C, D neg blood. (If it is allo or auto anti D, makes no difference (as long as the patient is c positive)).

Peter

[Mabel Adams]

Her auto control is negative and she is pregnant.

[Yanxia]

Thanks for your post,Rh-fan . You say the anti-D is auto, do you mean the weak D type 2 produce anti-D it also have the components against his own epitope?

[Rh-fan]

That is what I suspect, Shilly.

Although the auto controle and the Direct antiglobulin test is negative we sometimes see anti D (and anti G) antibodies in the eluate made of the patient cells (also when they have not been transfused) in these kind of cases.

[Mabel Adams]

So do I understand correctly that this auto antibody would not be strong enough to cause a positive auto-control but would be able to be eluted from the patient's own cells? Is she a candidate for RhIG during this pregnancy then?

[Rh-fan]

Yes, it is the combination of weak antigen expression and a weak antibody.

But that is the case when we have some more proof/info on the genotyping.

The RhIG is not nessecerry because already anti D is present, but when we know we are dealing with a weak D type 2 we do not give RgIG, although they can make an auto anti D. RhIG is used to prevent allo anti D formation.

[Mabel Adams]

Will this auto-anti-D (and G) cause HDFN in the R1r or R1/(whatever mom's weird D+ genes are) baby? Dad is R1R1.

[Malcolm Needs ☆]

Almost certainly not.

Auto-antibodies, even in a case of fairly strong panagglutinins, have rarely, if ever, caused clinically significant HDFN.

Anti-G, if it causes anything, is much more likely to cause HDN than HDF, but usually only results in a positive DAT, with no clinical sequalae for the baby.

It is also rare for an anti-D, under such circumstances, for the anti-D, even if it is an alloanti-D, to cause clinically significant HDFN, unless the titre is reasonably high (over about 32).

[Mabel Adams]

Of course, we may have the additive effect on the baby of the anti-C plus these other antibodies. Do you agree that it is reasonable for them to start following the baby with ultrasound rather than titers since there are so many variables to the antibody picture and we have at least one titer that is 64?

[Malcolm Needs ☆]

But again Mabel, which of the antibodies has a titre of 64? If it is the anti-C or anti-G, then I wouldn't worry too much. The very good chances are that it will cause slight HDN (positive DAT, or may need phototherapy), rather than clinically significant HDN.

That having been said, as MCA Doppler/ultrasound is non-invasive, monitoring the pregnancy by these methods will harm neither Mum nor baby.

[Mabel Adams]

The 64 titer is with r'r' cells, so both anti-C & G. The titer with R2R2 cells is <1. ARC said the titer with R1R1 cells was 8 which is a bit strange since those cells have the C & G antigens as well as the D, but they were blaming steric interference. We got a titer of 4 with r'r cells (we did not have any double-dose C that were D neg). We concluded that it was safest to follow with ultrasound etc. rather than titers, but I am glad there is an option these days besides just amniocentesis. We also decided against giving RhIG. Let me know if you disagree.

[Malcolm Needs ☆]

No, I totally agree with what you done.

I do have one question though, and that is why you would want to titre the anti-C (+G) against red cells expressing a "double dose" of C (and G)? Unless you are suggesting that the anti-C (+anti-G) is an auto (which I KNOW you are not) the baby must be an obligate "single dose" for both antigens, and so an r'r red cell used in the titration would closer reflect the the in vivo "clinical power" of the antibody.

Edited February 14, 2012 by Malcolm Needs
Originally left a bit out.

[Mabel Adams]

I've heard that logic before about doing titers against single-dose cells, but I don't know what sort of cells were used in the original titration studies when they decided that a titer of 16 meant anti-D was a significant risk. Since titers don't always correlate well with the severity of HDFN it seems to me we should use whatever cells were used when what little correlation we have was determined. I assume the original was with double-dose cells because that is what we were taught to use until 10 or 20 years ago when someone brought up the argument about the baby being single-dose (unless of course there is a donor egg) but I might be wrong. Do you know?

[Malcolm Needs ☆]

I'll have a ferret around in my oldest text books and older reprints of papers and get back to you Mabel.

[Malcolm Needs ☆]

My earliest edition of Mollison (the 6th, published in 1979) talks of titrations being badly correlated with severity of HDFN, but does not talk about the red cells expressing the D antigenin a "homozygous" or "heterozygous" state. Actually, given the little we knew about the D antigen, more than 30 years ago, and the fact that it was thought that anti-D did not show "dosage", I am not too surprised about that.

I will keep looking.

[Malcolm Needs ☆]

My first edition of Race and Sanger (Race RR, Sanger R. Blood Groups in Man. 1st edition. Blackwell Scientific Publications, 1950) alludes to the use of red cells expressing "heterozygotic" antigens in titration, but not directly to do with titrations during pregnancy.

I'll keep looking.

[Mabel Adams]

Maybe the article in Transfusion a few (probably quite a few) years back on the critical titer for Fya has a reference to the original D titer work.