Collaboration of TCR-, CD4- and CD28-mediated signalling in antigen-specific MHC class II-restricted T-cells.
A previously developed experimental system was applied to obtain qualitative and quantitative data on the contribution of TCR-, CD4- and CD28-mediated signalling in the activation of an antigen specific T-cell hybridoma. All the three signal transducing receptors were stimulated by their natural ligands, and intermediate and late responses of an I-Ed restricted, CD4 +, influenza HA specific murine T-hybridoma (IP-12-7) were monitored by measuring the concentration of intracellular calcium [Ca2+]i and secreted IL-2. This type of analysis of T-cell activation revealed: (i) calcium mobilization induced by peptide loaded APC requires rapid conjugate formation; (ii) a direct correlation between the magnitude of the intermediate and the late responses was observed as a consequence of differential TCR ligation modulated by peptide dose or by the presence CD4; (iii) considering the APC/peptide and T/APC ratios, the concentration dependence of the intermediate and late responses was similar in both assays but a substantial difference in the sensitivity of the two methods was observed; (iv) CD4 mediated signalling has a co-stimulatory effect predominantly at suboptimal in vitro conditions; and (v) sustained increase of [Ca2+]i as well as the production of high concentrations of IL-2 is highly dependent on the CD28-B7 interaction. These results demonstrate that distinct peptide doses and the presence or absence of CD4 result in quantitative changes in T-cell responses, while the degree of CD28 mediated signalling has a qualitative affect on the outcome of T-cell activation, revealed by complete or partial inhibition of IL-2 secretion as a result of limited CD28-B7 interaction as well as by alteration in the duration and time kinetics of the calcium response.
Gogolák
P
P
Department of Immunology, L. Eotvos University, God, Hungary.
Réthy
B
B
Horváth
A
A
Tóth
G K
GK
Cervenák
L
L
László
G
G
Rajnavölgyi
E
E
D000818:Animals; D000938:Antigen-Presenting Cells / Q000276:immunology; D018106:CD28 Antigens / Q000276:immunology*; D015704:CD4 Antigens / Q000276:immunology*; D002118:Calcium / Q000276:immunology; D004305:Dose-Response Relationship, Drug; D000949:Histocompatibility Antigens Class II / Q000276:immunology*; D006801:Humans; D008213:Lymphocyte Activation / Q000276:immunology; D051379:Mice; D008807:Mice, Inbred BALB C; D010455:Peptides / Q000276:immunology; D011948:Receptors, Antigen, T-Cell / Q000276:immunology*; D015398:Signal Transduction / Q000276:immunology*; D013601:T-Lymphocytes / Q000276:immunology*; D014407:Tumor Cells, Cultured
D018106:CD28 Antigens; D015704:CD4 Antigens; D000949:Histocompatibility Antigens Class II; D010455:Peptides; D011948:Receptors, Antigen, T-Cell; D002118:Calcium