Local and systemic cytokine responses during larval penetration in cattle experimentally infested with Hypoderma lineatum (Diptera: Oestridae)

Local and systemic cytokine responses were studied in 3 groups of cattle, with 4 animals each, experimentally infested with Hypoderma lineatum (De Villers) first instars (L1). The first group was undergoing a primary infestation (G-1), the second group was undergoing a secondary infestation (G-2) and the third group was infested for their third consecutive year (G-3). Cattle were infested with 25 L1 deposited on the skin. Blood and skin samples were taken at 0, 6, 12, 48, 96 and 144 h post-infestation (h.p.i.). Interleukin 10 (IL-10), IL-4 and interferon gamma (IFN-γ) production was studied by immunohistochemistry and sandwich ELISAs. IL-4⁺ cells showed a significant increase at 6 h.p.i. in both reinfested groups (G-2 and G-3) when compared with G-1. In all groups the number of IL-4⁺ cells decreased significantly at 48 h.p.i. IL-10⁺ cells increased in G-1 at 6 and 48 h.p.i., whereas in both reinfested groups increased at 12 h.p.i. with a peak at 48 h.p.i. IFN-γ⁺ cells showed a significant increment at 6 h.p.i. in all groups, followed by a rapid descent at 12 (G-1 and G-2) and 48 h.p.i. (G-3). Penetration of the skin by H. lineatum did not have any significant effect on IFN-γ serum concentrations and, except for IL-10 there were no correlation between local production and serum concentrations of cytokines. The increase of both Th1 (IFN-γ) and Th2-type cytokines (IL-4 and IL-10) indicates that bovine T-cell response during the first phases of the infestation by H. lineatum is apparently a Th0 response.