Modulation of cell cycle progression by CTLA4-CD80/CD86 interactions on CD4+ T cells depends on strength of the CD3 signal: critical role for IL-2.
Cytotoxic T-lymphocyte antigen 4 (CTLA4) is a well-studied T cell costimulatory receptor that is known to inhibit T cell activation. In this study, the relationship between strength of the first signal and costimulatory interactions on primary mouse CD4(+) T cells was investigated. CTLA4-CD80/CD86 interactions differentially modulate T cell cycling based on the mode of CD3 signal: Activation with plate-bound (pb) anti-CD3 generates a strong signal compared with a weak signal with soluble (sol) anti-CD3, resulting in approximately sevenfold higher amounts of interleukin (IL)-2 and an increase in cell cycling. Activation of T cells with sol anti-CD3 (weak signal) together with CTLA4-CD80/CD86 blockade lowers IL-2 production and cell cycling, demonstrating an enhancing role for these interactions. Conversely, blockade of CTLA4-CD80/CD86 interactions on T cells activated with pb anti-CD3 (strong signal) increases proliferation, which is consistent with CTLA4 as a negative regulator. Also, coculture of T cells with Chinese hamster ovary cells expressing CD80 or CD86 demonstrates that the strength of the primary signal plays an important role. It is important that modulation of IL-2 amounts leads to distinct alterations in the functional effects of CTLA4-CD80/CD86 interactions. On increasing IL-2 amounts, activation of T cells stimulated with sol anti-CD3 (weak signal) and CTLA4-CD80/CD86 blockade is greater compared with control. Concurrently, neutralization of IL-2 greatly reduces activation of T cells stimulated with pb anti-CD3 (strong signal) and CTLA4-CD80/CD86 blockade compared with control. These results underscore the importance of strength of first signal, CTLA4-CD80/CD86 interactions, and IL-2 amounts in modulating primary CD4(+) T cell responses.
Mukherjee
Sambuddho
S
Department of Biochemistry, Indian Institute of Science, Bangalore, India 560012.
Ahmed
Asma
A
Malu
Shruti
S
Nandi
Dipankar
D
D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology; D015703:Antigens, CD / Q000276:immunology*; D000943:Antigens, Differentiation / Q000276:immunology*; D018122:B7-1 Antigen / Q000276:immunology*; D051940:B7-2 Antigen / Q000276:immunology*; D017252:CD3 Complex / Q000276:immunology*; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology*; D060908:CTLA-4 Antigen; D002453:Cell Cycle / Q000276:immunology; D007376:Interleukin-2 / Q000276:immunology*; D051379:Mice; D008810:Mice, Inbred C57BL; D015398:Signal Transduction / Q000276:immunology
D000911:Antibodies, Monoclonal; D015703:Antigens, CD; D000943:Antigens, Differentiation; D018122:B7-1 Antigen; D051940:B7-2 Antigen; D017252:CD3 Complex; D060908:CTLA-4 Antigen; C556707:Ctla4 protein, mouse; D007376:Interleukin-2