We have a patient who has the known antibodies: anti-Fya,-C,-K,-Jkb. The patient now has a cold agglutinin and a warm auto antibody. The patient's race is black and phenotypes as Fya and Fyb negative. A 2 X @37C allogeneic adsorption was performed using R1R1 Fya+(cell A), R2R2 Fya-(cell , and rr Fya+(cell C). Given the patient's race, we wouldn't expect them to have an anti-Fyb. However, when the adsorbed sera from cell A and C was tested with Fyb positive cells it reacted 1+. If this were anti-Fy3, we should have expected it to be adsorbed out with the cell A and C and in turn have no reactivity with the Fyb positive cell (as a side note, the Fyb positive cell was negative for all the antigens to the previous known antibodies). All other common alloantibodies have been ruled out. Any ideas what could be causing the reactivity with the Fyb positive cells??????????????? An autoadsorption was also performed supporting the results of the allogeneic adsorption. Thanks!!