A monoclonal antibody blocking human T cell function

The possible functional role of T cell surface antigens defined by monoclonal antibodies was investigated. Five monoclonal anti-T cell reagents as well as an anti-Ia and anti-beta 2-microglobulin antibody were examined for their effect on T cell function. It was shown that an antibody termed anti-T3, reactive with all peripheral T cells, blocked T cell proliferative responses to soluble and cell surface antigens. This inhibition was seen when T lymphocytes were treated with as few as 10(4) anti-T3 molecules per cell. Although anti-T3 could block the generation of cytotoxic T cells in mixed lymphocyte culture, once generated, anti-T3 had no effect on cytotoxicity. In addition, anti-T3 abrogated the ability of T cells to provide help to B cells in a pokeweed mitogen-driven immunoglobulin system. More importantly, these functional effects were not seen with the other monoclonal antibodies. Both the appearance of this antigen in intrathymic ontogeny and its critical role in T cell function suggests that the T3 molecule is related to an important antigen recognition receptor or cell-cell interactions molecule.