IMMUNIZATION OF CATTLE BY INFECTION WITH COWDRIA-RUMINANTIUM ELICITS T-LYMPHOCYTES THAT RECOGNIZE AUTOLOGOUS, INFECTED ENDOTHELIAL-CELLS AND MONOCYTES

Peripheral blood mononuclear cells (PBMC) from immune cattle prolifera te in the presence of autologous Cowdria ruminantium-infected endothel ial cells and monocytes, Endothelial cells required treatment with T-c ell growth factors to induce class II major histocompatibility complex expression prior to infection and use as stimulators. Proliferative r esponses to both infected autologous endothelial cells and monocytes w ere characterized by expansion of a mixture of CD4(+), CD8(+), and gam ma delta T cells. However, gamma delta T cells dominated following sev eral restimulations. Reverse transcription-PCR analysis of cytokine ex pression by C. ruminantium-specific T-cell lines and immune PBMC revea led weak interleukin-2 (IL-2), IL-4, kind gamma interferon (IFN-gamma) transcripts at 3 to 24 h after stimulation. Strong expression of IFN- gamma, tumor necrosis factor alpha (TNF-alpha), TNF-beta, and IL-2 rec eptor alpha-chain mRNA was detected in T-cell lines 48 h after antigen stimulation. Supernatants from these T-cell cultures contained IFN-ga mma protein. Our findings suggest that in immune cattle a C, ruminanti um-specific T-cell response is induced and that infected endothelial c ells and monocytes may present C. ruminantium antigens to specific T l ymphocytes in vivo during infection and thereby play a role in inducti on of protective immune responses to the pathogen.