Description of a Qa-2 like alloantigen (Qa-m2)

Several new aspects of the chemistry, genetics and cellular distribution of the murine Qa-2 alloantigen were apparent in an analysis of this antigen using monoclonal antibodies recognizing a Qa-2-like antigen called Qa-m2. Immunoprecipitation and sodium dodecyl sulfate polyacrylamide gel electrophoresis analysis identified the Qa-m2 alloantigen as a two-chain structure composed of a 39 000 dalton heavy chain and a 12000 light chain which is probably β₂-microglobulin; the heavy chain was readily distinguished from that of H-2. In addition, the expression of Qa-m2 alloantigens on the cell surface was found to be controlled by the H-2D gene with H-2D^b strains carrying approximately 8-10 times greater amounts of Qa-m2 than strains carrying the H-2D^d or H-2D^q alleles. Finally, the Qa-m2 antigen, found predominantly on peripheral T cells, was present on only 10% of thymus cells. However, subpopulations of B cells (approximately 25% of all B cells) and bone marrow cells (15-20%) were also reactive. The monoclonal anti-Qa-m2 antibodies differed in their reactions from that reported for the conventional anti-Qa-2 sera, which must, therefore, be complex. The monoclonal antibodies may be useful reagents for functional analysis of T and B cell subpopulations.