Soluble CD4 suppress the antigen driven proliferative response of certain T cell clones specific for mycobacteria and for peptides by mycobacterial heat shock proteins

We have investigated the effect of soluble recombinant CD4 (sCD4) on the antigen specific (BCG, peptides of mycobacterial 65 kDa hsp) response of T cell lines or T cell clones. The majority of the antigen specific clones could be suppressed in their antigen driven response by the addition of sCD4, while others, including the parental polyclonal T cell line, were not. The suppression of the specific T cell response was reversed by the addition of anti-CD3, did not affect the proliferative response to IL-2, and was independent of the amount of antigen. A decreased capacity to produce IFN-γ in response to the antigen by the addition of sCD4 was seen only with those clones that were also inhibited in their specific proliferative response. This model may be used to delineate further the interaction between T cells and the antigen presenting cell, and the finding may limit the possible in vivo use of sCD4 in the therapy of human immunodeficiency virus (HIV) infections.