Patterns of costimulation of T cell clones by cross-linking CD3, CD4/CD8, and class I MHC molecules.
The ability of mAb to class I MHC molecules, CD3, or CD4/CD8 to stimulate human T cell clones alone or in combination was examined. Cross-linking each of these surface Ag with appropriate mAb and goat anti-mouse Ig (GaMIg) resulted in a unique pattern of increase in intracellular free calcium ([Ca2+]i) and different degrees of functional activation. Cross-linking class I MHC molecules provided the most effective stimulus of IL-2 production and proliferation. Cross-linking more than one surface Ag induced a compound calcium signal with characteristics of each individual response. Cross-linking CD3 + HLA-A,B,C caused a rapid and prolonged increase in [Ca2+]i and synergistically increased IL-2 production and proliferation of all clones. Cross-linking CD3 + CD4/CD8 also generated a compound calcium signal and increased IL-2 production and DNA synthesis. Purposeful inclusion of CD3 was not required for costimulation as cross-linking HLA-A,B,C + CD4/CD8 also increased [Ca2+]i, IL-2 production, and proliferation. Cross-linking three surface Ag, CD3 + HLA-A,B,C + CD4/CD8, resulted in the greatest initial and sustained [Ca2+]i, IL-2 production, and DNA synthesis. Although there was a tendency for the various stimuli to increase both [Ca2+]i and functional responsiveness, neither the magnitude nor duration of the increased [Ca2+]i correlated with the amount of IL-2 produced or the ultimate proliferative response. To determine whether costimulation required that the various surface molecules were cross-linked together, experiments were carried out using isotype specific secondary antibodies. Augmentation of [Ca2+]i and costimulation of functional responses were noted when class I MHC molecules were cross-linked and CD3 was bound, but not cross-linked. Similarly, costimulation through CD3 and CD4/CD8 was observed when CD4/CD8 was cross-linked and the CD3 complex was engaged by an anti-CD3 mAb which was not further cross-linked. In contrast, costimulation by class I MHC molecules and CD4/CD8 was only observed when these molecules were cross-linked together. These data demonstrate that cross-linking class I MHC determinants or CD4/CD8 provides a direct signal to T cell clones that can be enhanced when CD3 is independently engaged. The results also indicate that T cell clones can be stimulated without engaging CD3 by the combination of signals delivered via class I MHC molecules and CD4/CD8, but only when these determinants were cross-linked together. These studies have demonstrated that these cell surface molecules differ in their capacity to deliver activation signals to T cell clones and also exhibit unique patterns of positive cooperativity in signaling potential.
Wacholtz
M C
MC
Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas 75235.
Patel
S S
SS
Lipsky
P E
PE
D000276:Adjuvants, Immunologic / Q000502:physiology; D000818:Animals; D000911:Antibodies, Monoclonal / Q000502:physiology; D000945:Antigens, Differentiation, T-Lymphocyte / Q000276:immunology / Q000378:metabolism*; D017252:CD3 Complex; D002118:Calcium / Q000378:metabolism; D002999:Clone Cells / Q000276:immunology / Q000378:metabolism; D003432:Cross-Linking Reagents; D000939:Epitopes / Q000276:immunology; D015234:HLA-A Antigens / Q000276:immunology / Q000378:metabolism; D015235:HLA-B Antigens / Q000276:immunology / Q000378:metabolism; D015236:HLA-C Antigens / Q000276:immunology / Q000378:metabolism; D015395:Histocompatibility Antigens Class I / Q000276:immunology / Q000378:metabolism*; D006801:Humans; D007376:Interleukin-2 / Q000096:biosynthesis; D008213:Lymphocyte Activation; D051379:Mice; D011948:Receptors, Antigen, T-Cell / Q000276:immunology / Q000378:metabolism*; D015398:Signal Transduction; D013601:T-Lymphocytes / Q000276:immunology / Q000378:metabolism*
D000276:Adjuvants, Immunologic; D000911:Antibodies, Monoclonal; D000945:Antigens, Differentiation, T-Lymphocyte; D017252:CD3 Complex; D003432:Cross-Linking Reagents; D000939:Epitopes; D015234:HLA-A Antigens; D015235:HLA-B Antigens; D015236:HLA-C Antigens; D015395:Histocompatibility Antigens Class I; D007376:Interleukin-2; D011948:Receptors, Antigen, T-Cell; D002118:Calcium