title: Staphylococcus enterotoxin A modulates interleukin 15-induced signaling and mitogenesis in human T cells.
abstract: T cells expressing the appropriate T-cell receptor Vbeta chain proliferate in response to Staphylococcus enterotoxin A (SEA) pulsed antigen-presenting cells (APC), whereas other T cells do not (SEA "non-responders"). Activated human T cells express MHC class II molecules that are high affinity receptors for SEA. Here we show that, in the absence of APC, SEA induces a profound inhibition of IL-15-driven proliferation in MHC class II+, human SEA-"responder" T-cell lines. In contrast, proliferation induced by phorbol esther (PMA) was enhanced by SEA. The inhibitory effect on cytokine-mediated mitogenesis correlates with an inhibition of IL-2Rbeta expression and ligand-induced tyrosine phosphorylation of IL-2R. Cyclosporin A (CyA), an inhibitor of the protein phosphatase (PP2B) calcineurin, strongly inhibits the SEA-induced modulations of cytokine receptor expression. Moreover, CyA inhibits both the anti-mitogenic effect of SEA on cytokine-induced proliferation and the pro-mitogenic effect of PMA. In contrast, inhibitors of PP1, PP2A, protein kinase C (PKC), phosphatidyl-inositol-3-kinase (PI-3K) and mammalian target of rapamycin (mTOR) are unable to inhibit the effects of SEA. In a SEA "non-responder" T-cell clone obtained from the affected skin of a patient with psoriasis vulgaris, SEA does not inhibit IL-2Rbeta expression and IL-15-driven proliferation. On the contrary, SEA enhances IL-15- and IL-2-induced proliferation via a CyA-sensitive pathway in this T-cell clone. In conclusion, the present data show that (i) SEA selectively inhibits IL-15- (but not PMA-) mediated proliferation in SEA "responder" T cells, (ii) SEA enhances cytokine-driven growth in psoriasis T cells with a "non-responder" phenotype, and (iii) crosstalk between SEA receptors and the IL-15R (and IL-2R) pathway is mediated via a PP2B-dependent and PP1/PP2A-, PKC-, PI-3 kinase- and mTOR-independent pathway in human T-cell lines.
authors.affiliation: Institute of Medical Microbiology and Immunology, University of Copenhagen, Denmark. J.Gerwien@sb.immi.ku.dk
authors.forename: J
authors.initials: J
authors.lastname: Gerwien
authors.forename: K
authors.initials: K
authors.lastname: Kaltoft
authors.forename: M
authors.initials: M
authors.lastname: Nielsen
authors.forename: M B
authors.initials: MB
authors.lastname: Nielsen
authors.forename: A
authors.initials: A
authors.lastname: Svejgaard
authors.forename: C
authors.initials: C
authors.lastname: Geisler
authors.forename: C
authors.initials: C
authors.lastname: Röpke
authors.forename: N
authors.initials: N
authors.lastname: Odum
mesh_terms: D002455:Cell Division / Q000187:drug effects; D002460:Cell Line; D016572:Cyclosporine / Q000494:pharmacology; D004768:Enterotoxins / Q000494:pharmacology*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006801:Humans; D019409:Interleukin-15 / Q000494:pharmacology*; D007376:Interleukin-2 / Q000494:pharmacology; D008213:Lymphocyte Activation / Q000187:drug effects; D000081082:Phosphoinositide-3 Kinase Inhibitors; D010766:Phosphorylation; D011493:Protein Kinase C / Q000037:antagonists & inhibitors; D053647:Receptors, Interleukin-15; D015375:Receptors, Interleukin-2 / Q000378:metabolism; D015398:Signal Transduction; D013601:T-Lymphocytes / Q000166:cytology / Q000187:drug effects* / Q000276:immunology*
chemical_list: D004768:Enterotoxins; D004791:Enzyme Inhibitors; C508024:IL15RA protein, human; D019409:Interleukin-15; D007376:Interleukin-2; D000081082:Phosphoinositide-3 Kinase Inhibitors; D053647:Receptors, Interleukin-15; D015375:Receptors, Interleukin-2; C026066:enterotoxin A, Staphylococcal; D016572:Cyclosporine; D011493:Protein Kinase C