Immunocytochemical changes in the duodenum following Trichostrongylus colubriformis infection in sheep

Abstract

Monoclonal antibodies to ovine immune cell surface markers were used in an immunocytochemical study to determine the effect of lactation on mucosal cell populations. Lactating, barren and parasite-naive animals were challenged with 20,000 infective L₃ Trichostrongylus colubriformis, larvae and using a panel of five monoclonal antibodies, cell populations containing the following markers were quantified: CD4⁺, CD8⁺, T19 (τδ), CD5⁺ and mast cells. A significant difference (p < 0.1) was detected in the numbers of CD4⁺ and mast cell populations among the various treatment groups. Lactating sheep exhibited higher numbers of CD4⁺ T cells than the barren animals whereas in the later group, mast cells were markedly more abundant than in the naive animals. Though not significant, a difference in CD5⁺ and T19⁺ T cells was seen between the lactating sheep and the barren and naive animals. In contrast, no difference was detected in the CD8⁺ population regardless of the physiological status of the animal. The changes recorded in the mast cell population suggested that lactating animals displayed an impairment of the immune-mediated expulsion of parasitic worms which may be a reflection of altered lymphocyte subset populations.