Evidence implicating L3T4 in class II MHC antigen reactivity; monoclonal antibody GK1.5 (anti-L3T4a) blocks class II MHC antigen-specific proliferation, release of lymphokines, and binding by cloned murine helper T lymphocyte lines.
Monoclonal antibody GK1.5 recognizes a determinant, designated L3T4a, on the murine T cell surface molecule L3T4. The expression of L3T4a by functional murine T cell clones appears to correlate primarily with class II MHC antigen reactivity rather than with functional phenotype. In previous studies, antigen-specific cytolysis by a cloned class II MHC antigen(I-Ak)-reactive CTL line was found to be blocked entirely by monoclonal antibody (mAb) GK1.5, at a step before the lethal hit. In the present studies, we demonstrate that mAb GK1.5 profoundly blocks antigen-specific proliferation and release of lymphokines by cloned murine class II MHC antigen-reactive helper T lymphocyte (HTL) lines. Analysis of cloned T cell hybridomas, however, suggests that there exists clonal heterogeneity in the degree of inhibition of class II MHC antigen-specific function by mAb GK 1.5. Finally, we present evidence that mAb GK1.5 blocks class II MHC antigen-specific function by blocking class II MHC antigen-specific binding. The data presented here lend considerable support to the concept both that L3T4 and the human Leu-3/T4 molecules are similar and that L3T4 plays a role in class II MHC antigen-reactivity by murine T cells.
D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology* / Q000502:physiology; D000937:Antigen-Antibody Reactions; D001665:Binding Sites; D001666:Binding Sites, Antibody; D001667:Binding, Competitive; D002999:Clone Cells / Q000276:immunology / Q000378:metabolism; D000939:Epitopes / Q000276:immunology; D005260:Female; D006183:H-2 Antigens / Q000276:immunology*; D007376:Interleukin-2 / Q000096:biosynthesis; D008213:Lymphocyte Activation; D008222:Lymphokines / Q000096:biosynthesis*; D051379:Mice; D008810:Mice, Inbred C57BL; D008808:Mice, Inbred CBA; D010047:Ovalbumin / Q000276:immunology; D006377:T-Lymphocytes, Helper-Inducer / Q000276:immunology / Q000378:metabolism*
D000911:Antibodies, Monoclonal; D000939:Epitopes; D006183:H-2 Antigens; D007376:Interleukin-2; D008222:Lymphokines; D010047:Ovalbumin