Involvement of major histocompatibility complex class I antigens in T cell activation.
During the last few years ample evidence has been collected indicating a regulatory role for major histocompatibility complex class I antigens (Ag) in T cell activation. However, due to differential effects (stimulatory and inhibitory) of anti-class I antibodies (Ab) observed under different conditions, no coherent scheme of the mechanism of action of these Ag has emerged. Here, we present evidence that the mode of action of anti-class I Ab depends upon the presence or absence of monocytes/macrophages (M phi) in the culture. The Ab inhibit Ag presentation by binding to M phi. Coating of tetanus toxin -pulsed M phi with anti-class I Ab is sufficient to suppress T cell activation. On the contrary, these Ab enhance lectin- as well as phorbol ester-induced T cell activation in the absence of M phi. Cross-linking of class I Ag on T cell surface mobilizes cytoplasmic Ca2+, and also enhances the CD3-induced Ca2+ flux inside the cells indicating a functional relationship between CD3 and class I Ag. Though surface modulation and immunoprecipitation experiments do not indicate any physical association between these two types of molecules on the T cell surface, capping studies show that cross-linking of class I Ag induces an association of these Ag with CD3. Binding of anti-CD3 Ab enhances the strength of association between CD3 and class I Ag, and the former co-caps completely with the latter. Based on these observations we propose that during antigen presentation M phi (or Ag-presenting cells) and T cells, besides interacting via peptide--class II Ag/CD3--T cell receptor complex formation, also interact through class I Ag. The latter interaction may stabilize the contact formation between T cells and Ag-presenting cell and support T cell activation.
Dasgupta
J D
JD
Department of Pathology, Harvard Medical School, Dana-Farber Cancer Institute, Boston, MA 02115.
Egea
E
E
Relias
V
V
Iglesias
A
A
Gladstone
P
P
Yunis
E J
EJ
D000911:Antibodies, Monoclonal; D000938:Antigen-Presenting Cells / Q000276:immunology; D000945:Antigens, Differentiation, T-Lymphocyte / Q000502:physiology; D017252:CD3 Complex; D002118:Calcium / Q000378:metabolism; D003432:Cross-Linking Reagents; D015395:Histocompatibility Antigens Class I / Q000276:immunology*; D006801:Humans; D008213:Lymphocyte Activation / Q000276:immunology; D011233:Precipitin Tests; D011948:Receptors, Antigen, T-Cell / Q000502:physiology; D013601:T-Lymphocytes / Q000276:immunology*
D000911:Antibodies, Monoclonal; D000945:Antigens, Differentiation, T-Lymphocyte; D017252:CD3 Complex; D003432:Cross-Linking Reagents; D015395:Histocompatibility Antigens Class I; D011948:Receptors, Antigen, T-Cell; D002118:Calcium