Effect of ivermectin on the cellular and humoral immune responses of rabbits

The objective of this paper is to determine the effect of ivermectin administration on cell mediated (CMI) and humoral immunity (HI) of rabbits. CMI against dinitrochlorobenzene (DNCB) and sheep red blood cells (SRBC) in rabbits was determined by delayed-type hypersensitivity and macrophage engulfment assay (MEA), respectively; whereas, HI to Pasteurella multocida B2 vaccine and SRBC was determined by indirect haemagglutination assay (IHA) and Jerne hemolytic plaque formation assay (JHPFA), respectively. The rabbits were divided into four major groups (A through D) each subdivided into four sub-groups (1 through 4). Rabbits of group A served as vehicle control while those of groups B, C and D were treated with ivermectin at the dose rates of 200 mu g/kg, 400 mu g/kg and 600 mu g/kg b.w., respectively. Cellular immunity was determined in sub-groups 1 and 2 through DNCB and MEA, respectively while HI was determined in sub-groups 3 and 4 through IHA and JHPFA, respectively. The skin sensitivity to DNCB at 24 and 48 h and macrophage engulfment of SRBC were highest (P > 0.05) in rabbits administered with 600 mu g/kg b.w. The highest geometric mean titers (14.00 +/- 0.31) and number of plaque forming units (1860 +/- 0.75) were found in rabbits that received ivermectin at a dose of 600 mu g/kg b.w. followed, in order by the groups that received 400 mu g/kg, 200 mu g/kg b.w. and controls. Leukocyte counts were significantly higher in ivermectin-treated groups (C and D) than group A (vehicle control) and B (ivermectin at the rate of 200 mu g/kg). A graded dose immune response suggested an immunopotentiating effect of ivermectin at higher doses. (C) 2007 Elsevier Inc. All rights reserved.