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Anti-CD47 therapy interference with serology, but why DAT negative?

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In my lab we have investigated a number of patients who are on CD47 therapy.  They are always strongly pan-reactive by gel IAT, enzyme IAT and LISS tube IAT, but auto negative and DAT negative.  If they do have antibody bound to their red cells, why are they DAT negative?

 

Is it a similar mechanism as anti-CD38 therapy? Where DARA induces loss on CD38 on red cell surface, and so protects red cells from haemolysis?

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http://nybloodcenter.org/media/filer_public/2017/10/04/2017aabbpostervelliquetteserological_observationsfinalcp246.pdf

Apparently, weakly pos to negative DATs are common. Because the antibody covers cd47, the body sees the lack of cd47 and targets the cell for destruction. 

Edited by MaryPDX
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Just out of curiosity.. in your experience, how successful have you been able to remove the CD47 interference?  I've read numerous adsorptions using enzyme treated cells have shown to do the trick.  Also, the Immucor anti-IgG clone that doesn't detect IgG4, but we haven't seen these type patients yet and are anticipating seeing them soon.

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On ‎12‎/‎3‎/‎2017 at 1:40 PM, MaryPDX said:

 

http://nybloodcenter.org/media/filer_public/2017/10/04/2017aabbpostervelliquetteserological_observationsfinalcp246.pdf

Apparently, weakly pos to negative DATs are common. Because the antibody covers cd47, the body sees the lack of cd47 and targets the cell for destruction. 

Thank you so much for this - very useful.  (And for once.......we have the right reagent!!! - Go Immucor!)

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I am not familiar with the Immucor AHG that does not detect IgG4.  When using Immucor's AHG for testing patients after Dara treatment do you still see pan-agglutination?  We are currently sending patients treated with Daratumumab  to ARC reference lab for DDT treatment and transfusing K- blood if no antibodies are identified.  After a molecular phenotype has been done we consider transfusing phenotypically similar blood without an antibody workup which requires a signed deviation form per patient.  Both options are time consuming and expensive.

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1 hour ago, Patty said:

I am not familiar with the Immucor AHG that does not detect IgG4.  When using Immucor's AHG for testing patients after Dara treatment do you still see pan-agglutination?  We are currently sending patients treated with Daratumumab  to ARC reference lab for DDT treatment and transfusing K- blood if no antibodies are identified.  After a molecular phenotype has been done we consider transfusing phenotypically similar blood without an antibody workup which requires a signed deviation form per patient.  Both options are time consuming and expensive.

Patty, you may be getting your markers mixed up. Daratumumab reacts with CD38 (not CD47). It is an IgG1 antibody and reacts nicely with Immucor's reagent.

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On ‎12‎/‎4‎/‎2017 at 5:12 AM, BBNC17 said:

Just out of curiosity.. in your experience, how successful have you been able to remove the CD47 interference?  I've read numerous adsorptions using enzyme treated cells have shown to do the trick.  Also, the Immucor anti-IgG clone that doesn't detect IgG4, but we haven't seen these type patients yet and are anticipating seeing them soon.

Our facility hasn't started CD47 yet, but anticipate that may happen in 2018.  I've been dredging through the internet to find anything, which is how I found the NY blood center pdf.  Besides the use of Immucors Gamma-clone IgG antisera (for antibody screens), I haven't seen anything mentioned on how to avoid it. 

I was thinking along the line of using Platelets (which have cd47 on them) to remove the antibody, but have seen nothing regarding if anyone has tried this.  The search continues....

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