Monocytes provide a novel costimulatory signal to T cells that is not mediated by the CD28/B7 interaction

Julia G. Johnson, Marc Jenkins

Research output: Contribution to journalArticlepeer-review

45 Scopus citations


Resting CD4+ T cells must receive nonspecific costimulatory signals from APC to produce maximal amounts of IL-2 in response to TCR signaling. The T cell-specific surface molecule CD28 is one protein that transduces a costimulatory signal following interaction with its ligand B7. We report here the identification of another contact-mediated costimulatory signal provided by the human histiocytic line U937 and by purified monocytes. Although this monocyte-derived costimulus is not transduced by the CD28/B7 interaction, it synergizes with the CD28 signal to elicit maximal IL-2 production from freshly isolated T cells. IL-2 production by previously activated CD8+ T cells depends on the monocyte-derived costimulatory signal, although memory CD4+ T cells respond well to either the monocyte-derived costimulus or B7- derived costimulation. In contrast, IL-2 secretion by naive T cells appears to require the synergistic interaction between both costimulatory pathways. These results suggest that the array of costimulatory ligands expressed by various APC affects the magnitude of the T cell response and also which T cell subsets are stimulated.

Original languageEnglish (US)
Pages (from-to)429-437
Number of pages9
JournalJournal of Immunology
Issue number2
StatePublished - Jan 15 1994


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