Functional activity of draining lymph node cells of cattle following immunisation with Theileria annulata infected cell lines

Immunisation of cattle with in-vitro propagated Theileria annulata infected cell lines induces a protective immune response in the draining lymph node (DLN) whereas this is the site of immune failure in case of sporozoite infection. The activation state of DLN cells were undertaken to know how the response develops. Immunised animals showed a biphasic immune response. Ist response against immunising cell line, when the DLN cells harvested 4 days after immunisation showed a reduced response to Con A, slight proliferation to IL-2 and a strong proliferation to T. annulata (H) 769. DLN cells harvested 9 days after immunisation showed peak proliferation against the immunising cell line with an increased response to IL-2. 2^nd response against the parasite, when DLN cells harvested 16 days after immunisation showed a decrease in proliferative responses to the immunising cell line with an increase in proliferative responses to T. annulata (auto.) cell line. Cell cycle analysis showed large number of cells into the S-phase of the cell cycle within 4 days after immunisation. About 75% more cells entered into the S-phase by day 9 after immunisation as compared to cells of the naive calf with 50% more in G₂/M as compared to day 4.50% more cells were observed in the S-phase of cell cycle on day 16 after immunisation as compared to cells of naive calf. A maximum of 13% occurred in the G₂/M phase. These studies further confirmed that the immune responses developed in the DLN after immunisation.