Strong induction of tyrosine phosphorylation, intracellular calcium, nuclear transcription factors and interferonγ, but weak induction of IL-2 in naı̈ve T cells stimulated by bacterial superantigen

The outcome of T cell receptor (TCR) engagement is controlled by the differential recruitment of a variety of pathways, depending on the nature of the TCR ligand. Studies on superantigens (SAGs) were among the first describing such differential signaling; however, reported results are inconsistent. We took a quantitative approach to reinvestigate this question. Using naı̈ve T cells from TCR transgenic mice, we found that compared to the antigenic peptide from pigeon cytochrome c, the SAG staphylococcal enterotoxin A very efficiently (100–2000-fold more sensitive on a weight basis) induced tyrosine kinase activity, intracellular calcium increase, and interferon (IFN)γ production. Up-regulation of CD25 and CD69 and proliferation were less efficiently induced (20–30-fold more sensitive), and interleukin (IL)-2 production was induced least efficiently (only 2-fold more sensitive). This differential activation profile that varies with the activation event analyzed is discussed with respect to the propensity for SAG to induce anergy.