Lymphocyte populations and their relationship to cell-mediated immune responses in aflatoxin-treated guinea pigs
Effects of aflatoxin on cell-mediated immunity were investigated in guinea pigs. Dose dependent reductions in skin test responses were observed in guinea pigs which received at least 0.040 mg/kg/day aflatoxin B(,1) equivalents (B(,1) eq) for 3 weeks. Reduced weight gains were apparent at the 0.020 mg/kg/day B(,1) eq level. Serum bile acids were elevated at low levels of aflatoxin ingestion, in guinea pigs which displayed normal skin test responsiveness and weight gain;Passive transfer of delayed type hypersensitivity (DTH) was used to evaluate T lymphocytes or macrophages from aflatoxin-treated guinea pigs. The skin test responses of both nontreated guinea pigs receiving peritoneal exudate cells (PEC) from aflatoxin-treated guinea pigs and aflatoxin-treated guinea pigs receiving PEC from nontreated guinea pigs were numerically lower, but not significantly different (P < 0.05), than that of controls. Variability in susceptibility to aflatoxin was noted among individuals within groups;A bacterial binding assay currently used to identify human lymphocytes was adapted for use in guinea pigs. Three lymphocyte markers were identified: Salmonella schottmulleri and Yersinia enterocolitica, which appear to label all or some guinea pig T lymphocytes in peripheral blood; and Brucella melitensis, identified as a marker for guinea pig B lymphocytes in peripheral blood. Lymphocytes from spleen, thymus, and lymph node had different binding capacities than lymphocytes in peripheral blood, reflecting perhaps maturational differences among lymphocytes from different sources;Lymphocytes from nontreated and aflatoxin-treated guinea pigs were counted using immunofluorescence and bacterial markers. No changes occurred in absolute number of B or T lymphocytes identified by immunofluorescence. The number of S schottmulleri-positive lymphocytes closely approximated the numbr of T lymphocytes identified by immunofluorescence, except at the highest dose of aflatoxin used. At this level (0.060 mg/kg/day B(,1) eq) some T lymphocytes identified by immunofluorescence were refractory to binding of S schottmulleri;Aflatoxin impaired skin test responsiveness and passive transfer of DTH without causing quantitative changes in T or B lymphocyte populations in peripheral blood.