RESUMO
The effect of Lambda-cyhalothrin on the immune response was studied in rabbits exposed to the insecticide via food at concentrations of 1373.23, 686.76 or 343.38 ppm [equivalent to 1/10[th], 1/20[th] and 1/40[th] oral LD50, respectively] for 8 weeks. The humoral immune response was measured by determination of the antibody titre against sheep red blood cells [SRBC], a T - cell dependent antigen. Moreover, the cell-mediated immune response was evaluated by the delayed - type hypersensitivity reaction to tuberculin. The chemical treatment resulted in a dose - dependent suppression of both humoral and cellmediated immune responses as evidenced by decreased serum hemolysin titres and inhibition of the delayed-type hypersensitivity reaction to tubercluin, respectively. In addition, leucopenia, lymphopenia, depletion of lymphoid cells in the white pulps of spleen, mesentric lymph nodes and Peyer's patches and severe atrophy of thymus cortex were recorded. The serum total protein, albumin, globulin [specially gamma globulin], albumin/globulin [A/G] ratio and the organ to body weight ratios for spleen and thymus were significantly decreased with increasing the insecticide dosage. Moreover, different pathological alterations in liver, and brain were also observed. In conclusion, Lambdacyhalothrin exposure suppressed both humoral and cell-meditated immune responses in rabbits at the tested concentrations in a dose - dependent manner