A PRA specificity of B40, B44, B45 and B49 is most likely due to which antibody?

The specificity of panel reactive antibody (PRA) for the alleles B40, B44, B45, and B49 indicates a cross-reactive recognition pattern among these specificities, which is commonly associated with certain CREG (cross-reactive group) antibodies. The CREG antibodies are known to react with several HLA-B antigens that share defining epitopes.

The presence of B40, B44, B45, and B49 specifically points to the B12 CREG antibody. This CREG is well-documented for its ability to cross-react with various HLA-B types, thus indicating that this particular antibody has the capacity to bind to all four cited B antigens. Recognition of these HLA types by a single antibody is a key characteristic that helps in understanding the breadth of reactivity in immunological responses, especially in cases involving transplantation where matching for these specificities is crucial.

In the context of the other options, B7 and B8 CREG antibodies have distinct specificities that do not encompass the entire range of B antigens mentioned, while the possibility of having multiple specific antibodies would not yield the defined specificity observed here. The specificity for multiple antigens is more efficiently explained by the existence of a singular CREG antibody