IMMUNOLOGICAL FUNCTION IN HORSES AFTER NONSPECIFIC IMMUNOSTIMULANT ADMINISTRATION

Inactivated Propionibacterium acnes is a biologic response modifier fo r treatment of non-specific respiratory disease in horses. The objecti ves of this investigation were to determine alterations in phagocytic activity, phenotypic expression of lymphocyte subpopulations and lymph okine-activated killing cell response in healthy young horses. Samples were collected on day 0, 7 and 14 of the investigation. Blood samples were obtained via jugular venipuncture and pulmonary leukocytes were recovered via bronchoalveolar lavage (BAL). Commercially available P. acnes (Eqstim(R)) was administered intravenously on days 7, 9 and 11 o f the investigation. Fever was observed on days 8 and 10, indicating i mmune reaction. Total peripheral blood white cell count was increased (P<0.05) on day 14 after P. acnes administration compared to values on days 0 and 7. Total BAL fluid cell count decreased (P<0.01) on day 14 compared to values on days 0 and 7, which was characterized by a decr ease in total lymphocyte (P<0.01) and macrophage (P<0.01) counts. The proportion of lymphocytes in BAL fluid decreased (P<0.005) on day 14 c ompared to values on days 0 and 7, and the proportion of macrophages i ncreased (P<0.005) on day 14 compared to values on days 0 and 7. P. ac nes administration increased the total (P<0.05) and proportional (P<0. 05) counts of CD4+ T lymphocytes in peripheral blood. Bronchoalveolar lavage fluid proportion of CD4+ (P<0.05), CD5+ (P<0.001) and MHC II (P <0.05) lymphocytes increased on day 14 after P. acnes administration c ompared to values on days 0 and 7. Nonopsonized phagocytic activity in peripheral blood increased (P<0.0005) on day 14 after P. acnes admini stration compared to values on days 0 and 7. Lymphokine-activated kill ing cell activity in peripheral blood and BAL fluid leukocytes was enh anced (P<0.005) on day 14 after P. acnes administration compared to Va lues on days 0 and 7. Serum IgG and IgM concentrations were within lab oratory reference values and were not altered by administration of P. acnes. This investigation demonstrated immunostimulant and immunomodul atory properties of P. acnes, characterized by increased CD4+ T lympho cyte expression and LAK activity in peripheral blood and BAL fluid, in creased nonopsonized phagocytosis in peripheral blood leukocytes and d ecreased pulmonary cellularity. (C) 1998 Elsevier Science B.V. All rig hts reserved.