Recognition of a polymorphic monocyte antigen in HLA.

The serological recognition of 'new' gene products of the HLA system can be accomplished by selecting sera with strong leucocyte antibodies and testing these against a panel of cells obtained from donors which are compatible for the known HLA antigens with the antibody producer. This approach, which we termed the HLA-CAP approach (compatible with antibody producer), was essential in the recognition of what is now called the HLA-DR locus and of non HLA-linked T-cell subgroups. Using the same technique, we have defined here several sera recognizing a structure on monocytes similar to one of the alleles of the HLA-linked PL3 or secondary B-cell (SB) system, so far only recognized by cellular techniques.