An annexin 1 (ANXA1)-derived peptide inhibits prototype antigen-driven human T cell Th1 and Th2 responses in vitro

Background Annexin-1 (ANXA1 lipocortin 1) is a pleiotrophic protein produce d by many cell types including peripheral blood leucocytes. Although it has been shown to inhibit 'macroscopic' inflammatory processes in animal model s, its direct effects on antigen-activated human T cells have not been stud ied. Objective To test the hypothesis that ANXA1-derived peptides inhibit antige n-driven prototype Th1 and Th2-type human T cell responses of clinical rele vance and lectin-driven responses in vitro. Methods Peripheral blood mononuclear cells (PBMC) were isolated from 14 ato pic subjects sensitized to house dust mite allergen (Dermatophagoides ptero nyssinus, Der p) and purified protein derivative (PPD) of Mycobacterium tub erculosis. PBMC (1 x 10(6)/mL) were cultured with phytohaemagglutinin (PHA; 5 mug/mL; 4 days), Der p (25 mug/mL; 6 days), PPD (10 mug/mL, 6 days) or m edium control. Two ANXA1-derived peptides, Ac2-26 and AF-2 (5-500 muM), wer e assessed for possible inhibition of PHA-and antigen-induced T cell prolif eration (measured by H-3-thymidine uptake), while Ac2-26 was assessed for i nhibition of Der p-induced interleukin (IL)-5 release and PPD-induced inter feron-gamma (IFN-gamma) release (measured by ELISA). Comparison was made wi th dexamethasone as an established inhibitory control. Endogenous productio n by PBMC of cell surface-associated and intracellular ANXA1 in response to PHA, Der p and PPD in the presence and absence of dexamethasone was measur ed by specific ELISA. Results Both PHA- and antigen-induced T cellular proliferation were inhibit ed by dexamethasone. Although neither ANXA1-derived peptide significantly a ltered PHA-induced proliferation, both effected concentration-dependent red uctions in antigen-induced proliferation, Ac2-26 being the more potent. Pep tides of identical amino acid composition to Ac2-26 and AF-2, but of random sequence, were ineffective at equivalent concentrations. In addition. Ac2- 26 and dexamethasone inhibited Der p-induced IL-5 release and PPD-induced I FN-gamma release in a concentration-dependent fashion. Endogenous ANXA1 was detectable in PBMC, but at concentrations approximately 10(4)-fold lower, in molar terms, than the effective concentrations of the exogenously added, ANXA1-derived inhibitory peptides. Endogenous production was not significa ntly altered by any of the T cell stimuli employed in this study, in the pr esence or absence of dexamethasone. Conclusion In prototype Th1 and Th2-type human T cell responses, ANXA1-deri ved peptides can inhibit antigen-driven cellular proliferation and cytokine production.