Human macrophage-lymphocyte interaction in proliferation to soluble antigen: II. Characterization of lymphocyte binding to antigen-pulsed macrophage monolayers

Human peripheral blood T lymphocytes from individuals immune to tetanus toxoid (TT) or mumps soluble antigen can be depleted of cells capable of proliferating in response to these antigens by specific adsorption to antigen-pulsed macrophage (Mφ) monolayers. Specific adsorption is manifest by depletion of proliferative activity (measured by tritiated thymidine incorporation) in the fraction of T lymphocytes nonadherent to Mφ monolayers pulsed with the appropriate antigen. The occurrence of T lymphocyte-Mφ binding is supported by experiments which failed to detect cell-free factors or cells capable of inhibiting lymphocyte proliferation in the nonadherent lymphoid population. A quantitative analysis of the immunoadsorption assay suggests that proliferative activity representing at least 90% of that displayed by reciprocal control lymphocytes can be depleted on Mφ monolayers. Experiments employing varying numbers of adsorbing Mφ relative to T lymphocytes have established practical limits which predict the efficiency of adsorption. Kinetic studies indicate that specific adsorption occurs within 1 hr, with maximal levels or binding evident by 4–6 hr; binding remains stable for at least 16 hr. Specific adsorption is temperature dependent, occurring maximally at 37 °C, but not at all at 4 °C. T lymphocyte-Mφ interaction is complex and includes more than a recognition of pulsed antigen alone. This conclusion is supported by the finding that antigen-pulsed Mφ fail to absorb MLC-nonidentical allogeneic lymphocytes and that a heterologous antiserum directed against human Ia-like molecules (p23,30) inhibits specific T cell-Mφ binding.