PT  - JOURNAL ARTICLE
AU  - Kearney, E R
AU  - Walunas, T L
AU  - Karr, R W
AU  - Morton, P A
AU  - Loh, D Y
AU  - Bluestone, J A
AU  - Jenkins, M K
TI  - Antigen-dependent clonal expansion of a trace population of antigen-specific CD4+ T cells in vivo is dependent on CD28 costimulation and inhibited by CTLA-4.
DP  - 1995 Aug 01
TA  - The Journal of Immunology
PG  - 1032--1036
VI  - 155
IP  - 3
4099  - http://www.jimmunol.org/content/155/3/1032.short
4100  - http://www.jimmunol.org/content/155/3/1032.full
SO  - J. Immunol.1995 Aug 01; 155
AB  - The importance of CD28 costimulation to a primary T cell response in vivo was assessed in an adoptive transfer system where a small population of peptide-specific CD4+ TCR transgenic T cells can be physically tracked. Ag-dependent clonal expansion of the transgenic T cells in draining lymph nodes was blocked by cyclosporin A and required a CD28 signal that was completely inhibited by CTLA-4-Ig or a combination of anti-B7-1 and anti-B7-2 mAbs, but not by either Ab alone. In vivo treatment with the combination of anti-B7-1 and anti-B7-2 mAbs also blocked conversion of the Ag-specific T cells to the activated phenotype. In contrast, anti-CTLA-4 Fab greatly enhanced the in vivo clonal expansion of the Ag-specific T cells. These results suggest that Ag-driven proliferation and phenotype conversion of naive CD4+ T cells is dependent on CD28-derived signals and is inhibited by CTLA-4.