CO-STIMULATION-INDUCED RELEASE OF PRO-INFLAMMATORY CYTOKINE INTERLEUKIN-8 BY ALLERGEN-SPECIFIC T-CELLS

Chemokines, which include interleukin (IL)-8, are a family of pro-infl ammatory molecules with potent chemoattractant activity on neutrophils , as well as other cell types. IL-8 can be recovered from many inflamm atory sites. To test the hypothesis that Th2-type allergen-specific T cells, known to be the main cell type governing the allergic inflammat ion, are a source of IL-8 and to investigate whether IL-8 release is i nfluenced by the nature of the in vitro mitogenic or co-mitogenic stim ulation, cypress-specific T-cell clones (TCC) were generated from five allergic subjects during in vitro seasonal exposure to the allergen. Purified cypress extract was produced directly from freshly collected pollen and used for in vitro stimulation of PBMC bulk cultures. After 5 days priming and a further 7 day period of IL-2-driven cell expansio n, monoclonal antibodies to CD3, CD2 and CD28 were adopted for in vitr o restimulation of allergen-specific cell lines or, subsequently, seco ndary established TCC. The induction of apoptosis was detected by prop idium iodide (PI) cytofluorimetric assay. Basal and co-stimulation-ind uced IL-8 production was measured by an ELISA method. Both cypress-spe cific T-cell lines and TCC secreted appreciable amounts of IL-8. By cr oss-linking T-cell lines or Th2 CD4(+) TCC with CD3, CD2 or CD28 MoAbs , the authors observed a great stimulation-induced IL-8 secretion, pre ferentially after CD2 or combined CD2/CD28 stimulation. In addition, C D4(+) clones released large amounts of IL-8 into culture supernatants after CD2 stimulation while undergoing programmed cell death (30-40% h ypodiploid DNA profile of PI-stained cells). In contrast, CD3 crosslin king was unable to determine the release of IL-8 or the induction of a poptosis. Taken together, these results suggest that incomplete TcR en gagement by allergen may lead to the secretion of pro-inflammatory cyt okines with a contemporary induction of apoptosis in a significant num ber of target cells. This phenomenon may represent an additional way f or local recruitment of neutrophils and basophils.