Activation of human CD8⁺ suppressor T cells by an antigen-specific CD4⁺ T-cell line in vitro

We generated an antigen (streptococcal cell wall antigen)-specific T-cell line from peripheral blood mononuclear cells of a healthy donor with an intermediate response to streptococcal cell wall antigen. Proliferation of the T-cell line was completely blocked by a monoclonal antibody to HLA-DR. This line activated autologous CD8⁺ T cells in an antigen-specific manner in the presence of autologous monocytes. This activation was mediated by a factor derived from this line and was blocked by a monoclonal antibody against HLA class I molecules. The resultant CD8⁺ T blasts showed antigen-nonspecific suppression but no cytolytic activity. This antigen-specific generation of the CD8⁺ T-cell line in vitro by the antigen-specific CD4⁺ T-cell line is expected to contribute to analyses of functions of CD8⁺ T-cell subsets, particularly in the down-regulating system, at both cellular and molecular levels.