Submitted to: American Association of Veterinary Parasitologists Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: June 19, 1998
Publication Date: N/A
Ostertagiasis is one of the most important parasitic diseases of cattle in temperate areas of the world. The prevalence of the parasite is very high because immunity to reinfection arises very slowly and it is not completely protective. In vitro studies carried out with bovine lymphocytes from uninfected animals have demonstrated the inhibitory effect of O. ostertagi extracts on the growth of stimulated T cells. This effect was most evident when L4 soluble extracts were used, is weaker with adult extracts of the parasite, and was completely absent when using L3 extracts. A dose dependent inhibition of T cell growth was observed when adding L4 extracts to Con A stimulated cultures. Flow cytometric analysis of cell surface markers showed that IL-2 Receptor expression was significantly depressed when L4 extract was present in the culture when compared with control stimulated cultures. Other surface markers showed no changes, except for a slight decrease in CD3+ lymphocytes in cultures containing the L4 extract. Induction of cytokine messenger RNA was also studied using a competitive RT-PCR technique. Levels of IL-2, IFN-g, IL-4 and IL-13 expression were consistently lower in Con A stimulated cells exposed to the L4 extract. In contrast, expression of downregulating cytokines such as TGF-b was slightly increased in cells exposed to the L4 extract, and this extract itself showed binding activity in a ELISA specific for human TGF-b.