Differences in lymphocyte subpopulations from peripheral blood and lymphoid organs in natural caprine tuberculosis infection

Although the cell-mediated immune response is known to be a critical factor in host defence against intracellullar mycobacterial infection, the differ ent components of the T-cell response are unclear, particularly in caprine infection. In this study we examine the differences in the lymphocyte popul ation of peripheral blood, spleen and mediastinal and superficial lymph nod es in 11 naturally infected goats showing positive reactions in the compara tive tuberculine intradermal test. According to the different types of lesi on showing, the goats were classified into proliferative or exudative tuber culosis. The results obtained by fflow cytometry analysis indicated that th e main differences in peripheral blood were in the CD4 T-cell population, w hich decreased markedly in goats with exudative tuberculosis, while the CD8 and B cells increased in number. The gamma/delta T cells did not show sign ificant differences in either type of tuberculosis, while interleukin-2 rec eptor cells decreased slightly in the exudative tuberculosis. The CD4 : CD8 ratio was higher than 1 in goats with proliferative tuberculosis and lower than 1 in goats with exudative tuberculosis. In general, the lymphoid orga ns of the goats with exudative tuberculosis showed a significant increase i n the number of CD8 T cells (CD4: CD8 ratio of less than 1) whereas no sign ificant differences were observed in the CD4 T population between either ty pe of tuberculosis.