The distribution of the Qa-2 alloantigen on functional T lymphocytes.

The expression of Qa-2 on functional lymphocytes was investigated in vitro and in vivo by using a monoclonal anti-Qa-2 antibody. In vitro treatment of T cells with antibody and complement demonstrated that T cells mediating help or delayed-type hypersensitivity for anti-SRBC responses were Qa-2+. In addition, cytotoxic T cells and either their precursors or cells involved in their generation were Qa-2+, as were anti-HGG suppressor T cells. Panning techniques were also used to show that secondary suppressor T cells were Qa-2+ and that there may be heterogeneity in suppressor T cells defined by Qa-2 expression. In vivo treatment of mice with anti-Qa-2 resulted in decrease in immune responsiveness seen by i) prolongation of skin grafts with either H-2D or I-A differences, ii) suppression of delayed-type hypersensitivity, and iii) inhibition of T cell-mediated suppression. Finally, IgG, but not IgM, anti-body-forming cells were Qa-2+.