title: Involvement of the CD4 molecule in a post-activation event on T cell proliferation.
abstract: A monoclonal antibody (mAb) directed to a human leukocyte 55-kDa cell surface molecule with identical cellular distribution and biochemical properties to the CD4 was able to inhibit T cell proliferation induced either in a mixed lymphocyte culture or by activation with mAb anti-CD3, anti-CD2 or phytohemagglutinin. The inhibitory effect of anti-CD4 was observed in the absence of monocytes and was directly exerted on T4+ cells. This effect on cellular proliferation appears to be due to an inhibition of a postactivation event since the rise of cytoplasmic Ca2+ after activation with anti-CD3 mAb is not affected by the presence of anti-CD4 and the proliferation that occurs after an activation pulse of 3 h with ionophore and phorbol myristate acetate can be inhibited when the anti-CD4 is added after the pulse period. Kinetic studies demonstrated that the inhibition of cellular proliferation by anti-CD4 mAb was observed even if the antibody was added as late as 18-24 h after the initiation of the culture. The effect of this blocking anti-CD4 mAb on the interleukin (IL) 2/IL 2 receptor signalling pathways was also examined. The presence of anti-CD4 slightly affected the production of IL2. In fact, addition of exogenous recombinant IL2 at the initiation of the cultures did not restore the proliferative response. However, anti-CD4 had a strong inhibitory effect on the expression of IL2 receptors as analyzed by direct immunofluorescence cytometry. Taken together, these results indicate that the binding of the anti-CD4 mAb to T cells interferes with a late metabolic step being capable of abolishing the proliferative activity of fully activated cells.
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal; D000945:Antigens, Differentiation, T-Lymphocyte; D000954:Antigens, Surface / Q000276:immunology*; D002118:Calcium / Q000378:metabolism; D002460:Cell Line; D004261:DNA Replication; D006801:Humans; D007376:Interleukin-2 / Q000096:biosynthesis; D008213:Lymphocyte Activation; D051379:Mice; D011971:Receptors, Immunologic / Q000096:biosynthesis; D015375:Receptors, Interleukin-2; D013154:Spleen / Q000276:immunology; D013601:T-Lymphocytes / Q000276:immunology* / Q000378:metabolism
chemical_list: D000911:Antibodies, Monoclonal; D000945:Antigens, Differentiation, T-Lymphocyte; D000954:Antigens, Surface; D007376:Interleukin-2; D011971:Receptors, Immunologic; D015375:Receptors, Interleukin-2; D002118:Calcium