Complement Antibody?

[JoyG]

Just a quick question.  We have a Jkb which is not reacting with the plasma from the purple top but it is reacting with the serum in the red top which I would expect due to complement in the red top and not the purple but would it still react with Anti-IgG?  We did not use polyspecific.  Patient had a previous antibody, we ran out of plasma and went to the red top tube and low and behold the Anti-Jkb pops up reacting with IgG antisera.

[Malcolm Needs ☆]

Yes, this is quite normal.

Kidd antibodies, as a whole, tend to be IgG, a mixture of IgG and IgM, or just IgM, but the IgG part of the mixture tends to be IgG1 and/or IgG3 (sub-types of IgG that are "good" at setting off the classical complement pathway), so, if the antibody has become labile in vivo and in vitro using anti-IgG, you have more chance of detecting it with a complement detecting AHG.

However, monospecific anti-IgG is more sensitive for IgG antibodies than is polyspecific AHG, and so, once again, yes!

[Dr. Pepper]

Malcolm, am I missing something here? You give a nice description of the differences in reactivity one can obtain with polyspecific AHG vs. monospecific anti-IgG, but JoyG used the monospecific in both cases. The variable was serum vs. EDTA plasma. I would think that when using monospecific anti-IgG, having active complement or not would be a non-factor.

[galvania]

Silly question - what is in the purple top tubes?

Thanks

anna

[David Saikin]

EDTA specimen - we call them lavendar tops, some are pink also.

[Malcolm Needs ☆]

Sorry Phil, I've had a very bust couple of days. I WILL reply.

[galvania]

Well then that is a bit wierd.  I can quite get how you could get a reaction from serum and not EDTA-plasma if you are working with polyspecific Coombs, but I don't see how it would make a difference on anti-IgG only.  The only thing I can think is - (always presuming that the 2 specimens REALLY come from the same patient) - did you do the identification panel on the EDTA and then the crossmatch with the serum?  Or different types of cell?  And how positive was the positive result - strong, weak or 'there if you're really looking for it'?

Anna

[Malcolm Needs ☆]

Sorry (particularly to Phil) for taking so long to "re-reply", but I have been up to my eye balls over the last few days.

Yes, I agree that my first response did not make a lot of sense!

What I meant was that although the EDTA (purple top) would have negated the complement, if you are using a red top (serum), you have "two bites of the cherry", because the anti-Jkb is likely to be a mixture of IgG and IgM.

In such a situation, you have a case where the IgG bit of the anti-Jkb would be detected by the monospecific anti-IgG, but the IgM AND the IgG (given it was IgG1, IgG3 or a combination of IgG1 and IgG3) would, PERHAPS have led to the situation where the IgG and the IgM (which would also activate complement) would potentiate the agglutination of Jk(b+) red cells by "addition" of the factors.

OF COURSE, ALL THIS IS SPECULATION, AND I COULD BE TALKING COMPLETE NONESENSE!

[galvania]

Um Malcolm the only thing is that usually the anti-IgG in the polyspecific Coombs is the same as the the anti-IgG in the anti-IgG reagents, and unless they specifically say otherwise, both would cross-react with IgM.

And you would have the same amount of IgG and IgM in both EDTA and clotted blood, wouldn't you?  Or have I misunderstood?  I still think that there was a second, as yet undiscovered, factor that is responsible for this difference

[Malcolm Needs ☆]

Yes, I think you are right on both counts Anna.

I shall now go into hibernation for the Winter!!!!!!!!!!!!!!!!!!!!!