MODULATION OF THE PHENOTYPE AND FUNCTION OF BOVINE AFFERENT LYMPH CELLS DURING INFECTION WITH TRYPANOSOMA-CONGOLENSE

Alterations in the phenotype and function of cells isolated from bovin e afferent lymph were studied following tsetse-transmitted Trypanosoma congolense infection. Little alteration was observed in the output of the CD2+ T cells in the lymph, and within this population the CD4: CD 8 ratio remained relatively constant. By contrast, a marked decrease w as observed in the output of gammadelta T cells over the first 7 days following infection. The number of B cells increased between 2 and 6 d ays post-infection, and thereafter returned to pre-infection values. L ittle change was observed within the afferent lymph veiled cell popula tion. Examination of activation markers on the lymphocyte fraction of afferent lymph revealed a decrease in the number of cells expressing t he Interleukin-2 receptor alpha-chain from Day 5 post-infection. At th is time the expression of ACT 1, another early activation marker, was seen to increase. Afferent lymph cells collected pre-infection and on the first 4 days post-infection proliferated in response to stimulatio n with Concanavalin A in vitro. This response to mitogenic stimulation was completely abrogated from day five post-infection. However, these cells were not capable of suppressing the capacity of normal peripher al blood mononuclear cells to respond to mitogenic stimulus in co-cult ure assays. These studies suggest that although a degree of lymphocyte activation occurs in the afferent lymph following tsetse-transmitted infection with T. congolense, this may be sub-optimal owing to the imm unosuppression which appears to operate at the level of the skin and t he lymph nodes.