Submitted to: Research Workers in Animal Diseases Conference Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: 10/7/1999
Publication Date: N/A
Technical Abstract: Vaccines inducing protective immunity to a spirochetal-induced colitis of pigs predominately stimulate expansion of CD8+ T cells in vivo and in antigen-stimulated lymphocyte cultures. However, CD8+ T cells are rarely considered necessary for protection against extracellular bacterial pathogens. In the present study, pigs recovering from colitis resulting from experimental infection with Brachyspira (Serpulina) hyodysenteriae ha increased percentages of CD4-CD8+ (alpha alpha-expressing) T cells as compared to non-infected pigs. CD8+ (alpha alpha-expressing) cells were the predominant subset of lymphocytes that proliferated in antigen-stimulat ltures of peripheral blood mononuclear cells from B. hyodysenteriae- vaccinated pigs. Antigen-specific CD8+ (alpha alpha-expressing cells consisted of CD4-, CD4+, and gamma delta TCR+ cells. CD4-CD8+ (alpha beta-expressing) cells from vaccinated or infected pigs did not proliferate eupon in vitro antigen stimulation. Of the proliferating CD8 alpha alpha cells, the majority of the CD4+CD8+ cells were lymphoblasts, whereas approximately 50% of the CD4-CD8+ cells were small (potentially memory) cells. Addition of monoclonal antibodies (mAb) specific for either porcine MHC class I or II antigens inhibited B. hyodysenteriae-specific proliferative responses, whereas addition of mAb to porcine MHC II antigens, but not porcine MHC I antigens, inhibited the CD8 alpha alpha response. Depletion of CD4+ cells by cell sorting diminished but did not inhibit the antigen-specific CD8 alpha alpha proliferative response. These results demonstrate that CD8 alpha alpha T cells are essential for protective immunity to a spirochetal-induced colitis of pigs.