Characterization of a T-cell determinant defined by a monoclonal antibody (TH5.2) which is involved in the interleukin-2-producing and proliferative capabilities of T cells.
Utilizing an OKT-4-positive human T-cell lymphoma cell line as immunogen, we have produced a monoclonal antibody (MAb), designated TH5.2, which is capable of augmenting the interleukin-2 (IL-2) production and proliferation of antigen-activated T cells. TH5.2 MAb by itself is not mitogenic for T cells; the enhanced IL-2 production and proliferation requires costimulation with either antigen or mitogen. TH.2 MAb recognizes all peripheral blood T cells at varying intensities, but does not react with monocytes. Using dual-color fluorescence analysis, it was determined that TH5.2 MAb reacts at a higher intensity on Leu-3a-positive T cells compared to Leu-2a-positive cells. Sorting T cells on the basis of fluorescent intensity with TH5.2 MAb demonstrated that the T cells reacting at high TH5.2 intensity were able to respond to mitogen at a higher rate (5-10X), as well as produce higher concentrations of IL-2 in response to mitogen as compared to the low IL-2 intensity cells. Cytotoxically treating peripheral blood mononuclear cells (PBMC) with TH5.2 MAb plus complement, which resulted in an approximate 8% decrease in the total population, significantly reduced the ability of the cells to proliferate to both mitogen and antigen. Addition of recombinant IL-2 to the cultures was able to restore the proliferative capability of the cells. In further analyzing the ability of TH5.2 MAb to augment the proliferative capability of PBMC to antigen and mitogen stimulation in vitro, it was determined that TH5.2 MAb was capable of acting synergistically with antigen or mitogen in increasing the Il-2-producing capability of T cells. Taken together the data suggest that the TH5.2 determinants is involved in the proliferative capability of T cells and is functioning at the level of IL-2 synthesis and/or secretion.