cold autoantibodies

[eltonsey]

Hi

Is it possible to finde DAT positive with IgG only

Thanks

[Yanxia]

I don't think IgG is cold antibody.

Maybe there are some IgM is lossed by the test.

[Malcolm Needs ☆]

Yes.

The antibody in Paroxysmal cold haemoglobinurea is an auto-anti-P, and is IgG. Almost always, the DAT is positive for C3d only when the DAT is performed in tubes, because the IgG anti-P can be readily dissociated from the red cells. However, column agglutination technology will detect the presence of an IgG anti-P more readily becaus e there is no washing phase.

Now, although C3d is almost always found on the red cells in cases of PCH, just occasionally, so much complement has been consummed, that it cannot be replaced in the plasma quickly enough for it to be seen on the red cells as C3d (this, I might add, is highly unusual), and so it appears as IgG only in the DAT.

All that having been said, ABO maternal antibodies causing ABO HDN are also, of course, IgG, and these react readily in the cold. Although theses are not auto-antibodies, cold-reacting IgG auto-antibodies do exist, and so your findings, whilst very rare, are not unknown.