Phenotypic characterization of Eimeria tenella -specific chicken T-cells responding to in vitro parasite antigen re-stimulation.

Coccidiosis, caused by protozoan parasites of genus , is a disease with large impact on poultry production worldwide. It is well known that immunity is dependent on Th1-type responses. assessment of -specific T-cell activity would therefore be a valuable research tool but has so far proven difficult to establish. The present study aimed to evaluate induced blast transformation and CD25 expression in defined chicken T-cell populations as a measure of immunity. Three infection experiments were performed and PBMC and/or spleen cells were collected between 6 and 16 days after infection of chickens. Cells were stimulated with antigens and T-cell activation was assessed by immunofluorescence labelling and flow cytometry. The results consistently showed statistically significant specific activation of TCRα/β+T cells within a 'window' from 8 to 14 days after infection for both spleen cells and PBMC. Responding T-cells were identified as CD4+CD8-, CD4+CD8αα+ and CD4-CD8αβ+ where the CD4+CD8αα+ cells generally showed the highest responses. All three of these TCRα/βT-cell subsets showed significant induced blast transformation and/or CD25 expression albeit not always in concert on the same days after infection indicating complex kinetics of T-cell responses. In general, responses were higher for spleen cells compared to PBMC for all responding T-cell populations. This methodology shows promise to study -specific T-cells, e.g. to evaluate vaccine responses. Results indicated that a Th1-type response was induced and suggested a role for CD4+CD8αα+ cells in immunity.