Brief report: Why did two patients who type for HLA-B13 have antibodies that react with all Bw4 antigens except HLA-B13?

Two transplant candidates sensitized during pregnancy by a B*44:02 mismatch showed antibodies that reacted with an epitope defined by the 145R+82LR eplet pair shared by all Bw4 antigens in single allele Luminex panels except B13. Both eplets are on one or more alleles of the antibody producer and according to HLAMatchmaker, they are considered intralocus and interlocus matches which should not induce antibodies. The recently developed nonself-self paradigm for HLA epitope immunogenicity has offered a ready explanation why the pair of self-145R and self-82LR eplets on B*44:02 induced specific antibodies. This finding is consistent with the concept that alloantibody responses originate from B-cells with self-HLA immunoglobulin receptors.