Neutrophils rapidly produce Th2 cytokines in response to larval but not adult helminth antigen.

Host protective immunity to Haemonchus contortus (Hc) infection in parasite-resistant St. Croix (STC) sheep is initiated early and characterized by an influx of innate cells and robust interleukin-4 (IL-4) production, resulting in T-helper type 2 immune (Th2) responses. The purpose of these studies was to elucidate the source of early IL-4 production. Neutrophils were isolated from whole blood, and populations >98% purity were cultured with larval or adult antigen to access cytokine production. Interleukin-4 and IL-13 were measured in sample supernatant using an ovine-specific enzyme-linked immunosorbent assay (ELISA). Neutrophils exposed to HcLA peaked in IL-4 production at 30 minutes (STC, 3153.65 pg/mL and SUF, 4665.22 pg/mL). A similar trend was observed in IL-13 production by 6 hours (STC, 391.02 pg/mL and SUF, 419.6 pg/mL). Adult antigen stimulation resulted in low cytokine production when compared to HcLA stimulation (STC IL-4, 6.04 pg/mL and SUF, 8.05 pg/mL, respectively; STC IL-13, 10 pg/mL and 12.5 pg/mL; P < .001), and no breed differences were observed. Mixed immune cell assays revealed an ability of neutrophils to induce IL-4 production in peripheral blood mononuclear cell (PBMC). Taken together, these data implicate neutrophils as a potential effector cell responsible for Th2 initiation.