Use of a monoclonal antibody specifically non-reactive with T cells to delineate lymphocyte subpopulations.

Rat monoclonal antibody M1/69.16 reacts with a heat stable antigen of mouse commonly expressed in the majority of cell types in blood, spleen, bone marrow and thymus, including cells of erythroid, myeloid and lymphoid series. However, subpopulations of cells in lymphoid tissues can be identified which are non-reactive with this antibody using the fluorescence-activated cell sorter. All surface Ig positive cells seem to react with M1/69.16 while more than 96% of Ig negative cells in spleen and lymph nodes are M1/69.16 negative. Most cells (80%-90%) in the M1/69.16 negative populations in spleen lymph nodes and bone marrow express Thy-l. Thus, peripheral T cells are specifically non-reactive with this antibody. In contrast, approximately 95% of thymocytes react with M1/69.16, leaving a minor population which is negative. The negative population (5%) is enriched in cells expressing high amounts of H-2 antigen and those bearing H9/25 antigen which is specific for lymphocyte subsets, indicating that M1/69.16 negative thymocytes represent a specific subpopulation, possibly "mature' thymocytes.