CD28 affects the earliest signaling events generated by TCR engagement.
The efficiency and magnitude of T cell responses are influenced by ligation of the co-stimulatory receptor CD28 by B7 molecules expressed on antigen-presenting cells (APC). In contrast to most previous studies in which agonistic anti-TCR/CD3 and anti-CD28 antibodies were employed, here we have investigated the contribution of CD28 to T cell activation under physiological conditions of antigen presentation. Jurkat T cells and primary T cells from TCR-transgenic mice stimulated with superantigen and antigen, respectively, presented by B7-expressing APC were utilized. In both systems we show that inhibiting CD28/B7 interaction resulted in impaired TCR-induced tyrosine phosphorylation of the signal-transducing zeta chain and ZAP-70. Consistent with a blockade of TCR-proximal signaling events, Jurkat cells stimulated in the absence of CD28 ligation were found to have strongly diminished tyrosine phosphorylation of cellular substrates and downstream signaling pathways such as Ca2+/calcineurin, ERK/MAPK and JNK. Our results provide evidence for a role of CD28 in enhancing TCR signaling capacity during the earliest stages of T cell:APC interaction.
Department of Immunology, Institut Pasteur, Paris, France.
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D000818:Animals; D018122:B7-1 Antigen / Q000502:physiology; D018106:CD28 Antigens / Q000502:physiology*; D004268:DNA-Binding Proteins / Q000502:physiology; D016762:Genes, fos; D006801:Humans; D007376:Interleukin-2 / Q000096:biosynthesis; D048031:JNK Mitogen-Activated Protein Kinases; D019169:Jurkat Cells; D048670:MAP Kinase Kinase 4; D051379:Mice; D020929:Mitogen-Activated Protein Kinase Kinases; D020928:Mitogen-Activated Protein Kinases / Q000502:physiology; D050778:NFATC Transcription Factors; D009419:Nerve Tissue Proteins / Q000502:physiology; D009687:Nuclear Proteins; D011494:Protein Kinases / Q000502:physiology; D011948:Receptors, Antigen, T-Cell / Q000502:physiology*; D018808:Transcription Factor AP-1 / Q000502:physiology; D014157:Transcription Factors / Q000502:physiology
D018122:B7-1 Antigen; D018106:CD28 Antigens; D004268:DNA-Binding Proteins; D007376:Interleukin-2; D050778:NFATC Transcription Factors; D009419:Nerve Tissue Proteins; D009687:Nuclear Proteins; D011948:Receptors, Antigen, T-Cell; D018808:Transcription Factor AP-1; D014157:Transcription Factors; D011494:Protein Kinases; D048031:JNK Mitogen-Activated Protein Kinases; D020928:Mitogen-Activated Protein Kinases; D048670:MAP Kinase Kinase 4; D020929:Mitogen-Activated Protein Kinase Kinases