JOURNAL zyxwvutsrqp OF APPLIED TOXICOLOGY, VOL. zyxwvu 10(4), 245-250 (1990) Effects of Aflatoxin on Lymphoid Cells of Weanling Rat Raisuddin, K. P. Singh, S. I. A. Zaidi, A. K. Saxena and P. K. Ray? Preventive Toxicology Division. Industrial Toxicology Research Centre, PO Box 80, M. G. Marg, Lucknow zyxw 226 001. India Key words: aflatoxin B, zyxwvutsrqpo : lymphoid cells; macrophages; cytotoxicity. Aflatoxin (AF), the hepatocarcinogenic food contaminant produced by the Aspergillus flaws group of fungi, is known to interact with various vital processes, including the immune function. Effects of long-term treatment of three dose levels of aflatoxin B, (AFB,) on lymphoid cells of weanling rats were studied. AFB, treatment caused a reduction in body weight gain, significantly (P<O.Ol) at the 700 pg level. There was also a significant decrease in the weight of spleen and thymus in AFB,-treated animals in comparison to control. Similarly, AFB, depleted cell populations of thymus and bone marrow and WBC and RBC counts. There was a marked reduction in the population and phagocytic capacity of macrophages due to AFB, administration at dose levels of 350 and 700 pg kg-’ body weight. Macromolecular synthesis of DNA, RNA and protein in macrophages was affected, as there was significant inhibition in the incorporation of [’HI-thymidine, [’HI-uridine and [’HI- leucine. The hampered functioning of macrophages may be due to the cytotoxic action of AFB,. INTRODUCTION It has been demonstrated that several environmental chemicals, drugs and food additives adversely affect the immune system.’-5 The immunosuppression resulting from the exposure to a drug, chemical or food additive makes the host more susceptible to the challenges of bacteria, viruses, parasites, tumour cells and toxins.+’ It has also been demonstrated that immune competent cells and/or immune response per se can alter the metabolism and pharmacokinetics of foreign agents, resulting in hampered vascular clearance and tissue distribution and hence their catabolism.“’.” Aflatoxin (AF), a ubiquitously distributed food contaminant produced by the Aspergillus zyxwvutsrq fravus group of fungi, is described as a potent hepatocarcinogenic compound. More than two dozen types of aflatoxins have been known. differing in physico-chemical properties and toxicities. Besides the carcinogenic effects, AF is known to possess diverse biological activities, interacting with several vital processes. The immunosuppressive action of aflatoxin has also been described, particularly in and pigs.2’,’’ There are only a few reports on the effects of aflatoxin on the rodent immune system .27.24 Most of the studies demonstrate that birds and pigs are two highly suscep- tible species to aflatoxin immunotoxicity. It has been observed that a host pre-exposed to the aflatoxin becomes more susceptible to the challenges of various pathogenic organisms.’5 It can be presumed that aflatoxin, being a cytotoxic compound, may affect various lymphoid cells, including macrophages. Macrophages play an important role in host resistance to foreign agents and immune t Author to whom all correspondence should be addressed. responsiveness.’,’y-”’ In addition, macrophages happen to be initiators of various immunological response^.^^-^^ Furthermore, macrophages are of a cell type that may play a major role in tumour resistance and growth.’9 It appears that there is a paucity of data on the effects of AF on macrophages zyx in vivo, particularly in a host with a developing immune system. Aflatoxin, being too diverse in its biological reactivity in an event of exposure, may adversely affect the immune system of a host of low body weight. In view of this, it was felt pertinent to undertake the investigations on the effect of aflatoxin Bl (AFB,), the most potent and prevalent of all aflatoxins, on lymphoid cells and macrophage function, both quantitatively and qualitatively. Wean- ling rats were selected for this study, to find out the effects of aflatoxin exposure on the developing immune system. EXPERIMENTAL Chemicals Aflatoxin Bl, heparin and silicone oil were purchased from Sigma Chemical Co., St. Louis, MO; Hank’s balanced salt solution, RPMI-1640 medium and phos- phate-buffered saline (pH 7.2) were from Himedia, Bombay. Anti-sheep haemolysin was from Span Diag- nostics Pvt. Ltd., Surat and [‘HI-thymidine, [”I- uridine and [3HH]-leucine were procured from Bhabha Atomic Research Centre (BARC), Bombay. The rest of the chemicals used in the present study were purchased either from Sigma or from the local market. Animals Weanling male Wistar rats weighing 35 zy 2 2 g were obtained from ITRC Gheru Campus animal house 0260-437x/90/040245-06$05 .OO 0 1990 by John Wiley & Sons, Ltd.