| Popis: |
The main objective of this study was to identify immunological traits, which are associated with resistance and susceptibility, and particularly the relative significance of IgE antibodies in the response to GI nematodes in sheep. 100 Grey Suffolk Crosses that were grazing no pasture infected with T. circumcincta were ranked in order of their cumulative resistance to nematode infection as determined by their individual faecal egg counts from material taken from the middle, the end and the overall grazing season. The 10 lambs that had the lowest egg count rankings termed “responders” and 10 lambs that had the highest egg count rankings termed “non-responders” were selected for each of the three time periods. Serum samples collected from these lambs during the grazing season were tested on ELISA, using the specific T. circumcincta L3 antigen to detect concentrations of both IgE and IgA antibodies. Results showed that the responder lambs selected from the middle and overall grazing season showed significantly higher serum IgE antibody titres (p=0.04, p=0.03, respectively) than the non-responders towards the end of the season. A two-year study was then carried out to examine if any other relationships exist between responsiveness against GI nematodes in lambs and other immunological traits. 98 Scottish Blackface lambs that were grazing on pastures naturally infected with T. circumcincta were ranked in order of their responsiveness to nematode infection as described previously and 10 responders and 10 non-responders for each time period were selected. The study was followed for two grazing seasons. Results showed that in the first grazing season the most important markers of responsiveness to nematodes appeared to be the eosinophils and the numbers of IgE bearing cells. The second grazing season showed that the main marker of responsiveness seemed primarily in the IgE bearing cells, but no correlation was determined for circulating IgE antibody. |
