Antigen-specific antibody isotypes, lymphocyte subsets and cytokine profiles in cattle naturally infested by Hypoderma sp. (Diptera: Oestridae)

Antigen-specific antibody responses, T cell subsets and cytokine profiles were studied in 7 heifers naturally infested by Hypoderma sp. in Northwestern Spain. Immunoglobulin G (IgG) levels increased significantly at the end of the endogenous life cycle of the parasite (Mr). Similarly, IgG1 subclass increased considerably when first instars (L1) started their migration towards the back (Nv-Ja), whereas IgG2 increased earlier, coinciding with the arrival of L1 to the resting sites (Jn-Jl). Both subclasses decreased significantly when L3 began to leave the host. IgM levels and CD4 and CD8 profiles hardly oscillated throughout the life cycle of the parasite into the host. The CD4/CD8 ratio showed helper T cell predominance. Serum interferon-γ (IFN-γ) concentrations decreased from October to the end of the study. Interleukin 4 (IL-4) concentrations decreased in January and increased in February and May. There were a significant positive relationship between IL-4 and IgG2 subclass and a negative correlation between IFN-γ, IgG and IgG1 and also between IgM and CD2 and CD8 counts. These results suggest that in the early phases of natural primoinfestations by Hypoderma there is a slight predominance of a Th1 response, characterized by high IgG2 and IFN-γ levels, which is followed by a Th2 response with a clear predominance of IgG1 and IL-4.