Activated neutrophils can recruit Th17 and Th1 cells via chemokine release. (A) IL-17A⁺–enriched cells were evaluated by flow cytometry for intracellular IL-17A, IFN-γ, and IL-4 expression (to determine the percentages of positive cells). (B) Chemotaxis of IL-17A⁺–enriched cells toward supernatants (supnts) from IFN-γ–, LPS-, and IFN-γ plus LPS–conditioned neutrophils (n = 4). (C) IL-17A⁺-enriched cells, migrated in response to supernatants from resting (■) and IFN-γ plus LPS (γL)–activated (□) neutrophils (n = 4), were assessed for cytokine production by flow cytometry, on polyclonal stimulation. Bars represent the percentage of cells producing the indicated cytokine (mean ± SEM). (D) Real-time RT-PCR gene expression analysis performed with IL-17A⁺–enriched cells that have migrated toward supernatants from resting and γL-activated neutrophils. Results are expressed as mean normalized expression (MNE) units ± SE. One representative of 3 independent experiments with similar results is shown. (E-F) Chemotaxis of Th17, Th1, and (where indicated) Th2 clones toward: supernatants from γL-conditioned neutrophils (n ≥ 4; E); γL-conditioned supernatants, preincubated as indicated with αCCL2, αCCL20, and αCXCL10 neutralizing Abs (n = 4; F). *P < .05. ND indicates not done.