Characterization of bovine lymphocytes stimulated in vitro by Dictyocaulus viviparus homogenate

SUMMARY Adult Dictyocaulus viviparus homogenate induced proliferation of lymphocytes from naïve cattle. We characterized the responding cells by carboxyfluorescein diacetate succinimidyl ester (CFSE) loading, for detection of proliferation, and antibody labelling for cell surface molecules. Lymphocytes expressing CD4, CD8 and γ/δ TCR, rather than Ig expressing cells, proliferated after in vitro stimulation with D. viviparus homogenate. Of γ/δ TCR expressing cells, both CD8, WC1·1 and WC1·2 co‐expressing cells proliferated. Moreover, γ/δ T cells expressing MHC class II proliferated to a higher extent than those negative for MHC class II. Of CD4 and CD8 expressing lymphocytes, both those co‐expressing CD45R and CD45R0 proliferated. Among CD4 expressing lymphocytes, those that were CD45R0 positive had a larger proportion of proliferated cells than did CD45R positive cells. Compared to stimulation with Con A, the proportion of dividing cells after D. viviparus stimulation was smaller although the cells had divided more times. Furthermore, we also compared in vitro responses of peripheral blood mononuclear cells collected before and after two subsequent infections with D. viviparus , but no clear acquired responses could be detected. Overall, this suggests that most T lymphocytes are stimulated by the D. viviparus homogenate rather than any particular lymphocyte subpopulation.