Hi

We have a antenatal patient who has developed AntiJkb with titre 64 at 37 weeks. She has been planned for induction at 37 week due to rising titre. We received cord sample where DAT is positive IgG 3+ and also C3d 3+ and control negative. I haven't seen any case in my career with positive DAT on both IgG and C3d on baby sample. Hb and bilirubin Normal. 

What is the reason for DAT to be positive in C3d?  Does it suggest haemolysis?

 

Edited March 2, 20187 yr by gagpinks

I am wondering why the cord cells were tested with anti-C3? I believe it is not a common practice to test the cord with anti-C3 I just saw one too a few months ago, mine is a peripheral draw on a new born rather than cord, anti-IgG and -C3 pos.  I looked it up on Issitt's textbook. His references indicates that HDN due to complement activaton is an argument that has been challenged, as "C3 coating can be found on normail cord samples". I think if Hb and bili are normal C3 coating probably is not significant??  

 

Edited March 2, 20187 yr by dothandar

Both my friend and colleague Grant Webb and I have seen this with Kidd antibodies, but have not formally published this (see a couple of slides from one of my lectures), but none resulted in clinically significant HDFN (otherwise, of course, we would have published).

In my own case, dothandar, the reason we tested with anti-C3d was because we only had cassettes that contained an anti-C3d (see the photographs), and we only saw the positive DAT by anti-C3d by pure accident!

Reports of a Kidd antibody, causing a.pptx

Hi dothandar and Malcolm

These are the card we use in our lab as part of DAT protocol.  

Malcolm , I guess this finding is not clinically significant then. Is there any particular reason for DAT to be positive in C3d or cause is unknown?

Beautiful pictures. Thank you for sharing the cases. I have been on this site for almost a decade and never stopped learning from you guys! I wish we have these gel cards here in the States. There were sometimes we suspected problem due to IgA in DAT negative patients and those cards will be great to investigate such cases. 

I tend to attempt to "reinvent the wheel" due to my lack of historical knowledge and experience. I wonder if the infants cells from moms with Kidd blood group antibodies screened with anti-C3 in the past to see how many of them have turned up positive. It will be an interesting data to see if that has not already been done. 

Edited March 2, 20187 yr by dothandar

33 minutes ago, gagpinks said:

Malcolm , I guess this finding is not clinically significant then. Is there any particular reason for DAT to be positive in C3d or cause is unknown?

Cause unknown, I'm afraid.

My question would be - I wonder where  the complement is coming from?  Is this maternal complement  crossing the placenta that is being activated by the maternal anti- Kidd antibodies attaching to the baby's Kidd antigens?  Or is this the baby activating its own complement as a reaction to the antigen-antibody reaction?

and is the baby's Hgb and bili still normal?  Why isn't this baby haemolysing?

 

Baby is on phototherapy. 

51 minutes ago, gagpinks said:

Baby is on phototherapy. 

An awful ot of babies have phototherapy without having HDFN though.