Responses in the draining lymph node of cattle following immunisation with Theileria annulata infected cell lines.

Pathogenesis of tropical theileriosis is still unclear. However, it is known that the draining lymph nodes (DLN) are the site for aberrant T cell activation in the diseased animals whereas it is the site for initiation of immune response in case of vaccinated animals. The DLN responded to the Theileria annulata infected cell lines with the development of germinal centre by day 9 with light and dark zones. These germinal centres became reactive by day 12 with light and dark zones surrounded by a mantle zone generating serum antischizont antibody titer of 1:2560. By day 16, DLN generated a proper immune response with hyperplasia of reactive GC and serum antischizont antibody titer of 1:10240. This antibody peak was maintained until the 4th month after immunisation, antibody titers later declined by 6th month to 1:640 and 1:160 in calves whose DLN were removed on day 16 and 12 respectively.