title: Activation of resting T lymphocytes by anti-CD3 (T3) antibodies in the absence of monocytes.
abstract: The antigen receptor molecules on human T lymphocytes are noncovalently associated on the cell surface with the CD3 (T3) molecular complex. Perturbation of this complex with anti-CD3 monoclonal antibodies induces T cell activation. Previous studies have demonstrated that this process requires the participation of monocytes. In the present report, we demonstrate that purified, resting (G0 phase) T cells incubated with monoclonal anti-CD3 antibodies proliferate in response to purified interleukin 2 (IL 2), in a lymphokine dose-dependent fashion. Anti-CD3 antibody or IL 2 alone did not trigger cell division. The effect was specific for anti-CD3 antibodies because monoclonal antibodies reactive with other surface molecules (OKT4, OKT8, L368) were inactive. Furthermore, the same phenomenon was observed when anti-CD3 antibody Leu-4 (IgG1) was incubated with cells of individuals whose monocytes cannot process antibodies of the IgG1 subclass (Leu-4 nonresponders). In addition, both F(ab')2 and Fab fragments of anti-CD3 antibody OKT3 were also capable of rendering T cells receptive to the IL 2 growth signal. These data indicate that neither monocytes nor CD3 receptor cross-linking are required absolutely for resting T cell activation, provided that IL 2 is supplied exogenously. T lymphocytes treated with anti-CD3 antibodies proliferated in response to both purified mitogen-induced and recombinant IL 2. Antibodies to the IL 2 receptor (anti-Tac) inhibited the proliferation. Thus, the most likely mechanism for anti-CD3 antibody-mediated triggering is induction of IL 2 receptors.
mesh_terms: D000911:Antibodies, Monoclonal; D000945:Antigens, Differentiation, T-Lymphocyte; D000954:Antigens, Surface / Q000276:immunology*; D002478:Cells, Cultured; D006801:Humans; D007140:Immunoglobulin Fab Fragments / Q000276:immunology; D007376:Interleukin-2 / Q000276:immunology*; D008213:Lymphocyte Activation; D046911:Macromolecular Substances; D009000:Monocytes / Q000276:immunology; D011971:Receptors, Immunologic / Q000276:immunology; D015375:Receptors, Interleukin-2; D013601:T-Lymphocytes / Q000276:immunology*; D013997:Time Factors
chemical_list: D000911:Antibodies, Monoclonal; D000945:Antigens, Differentiation, T-Lymphocyte; D000954:Antigens, Surface; D007140:Immunoglobulin Fab Fragments; D007376:Interleukin-2; D046911:Macromolecular Substances; D011971:Receptors, Immunologic; D015375:Receptors, Interleukin-2