en Biological Sciences Biological Sciences Original Research: Basic Science in Medicine Original Research: Basic Science in Medicine The effect of ascorbic acid on blood histamine level and delayed-type hypersensitivity was studied in thirty male guinea pigs. Animals were sensitized to B.C.G., trichophytin and mallein during the first four weeks. The diet was ad libitum during this period. After this "sensitization period" animals w er e tested intradermally with tuberculin, trichophytin and mallein. The number and diameter of positive delayed type hypersensitivity responses (antigenic and cumulative scores) were evaluated as an effector state of cell mediated immunity. Animals were fed low, adequate or high ascorbate diets (0.5, 2.0 or 50 mg ascorbate x 100g body wt-1xd-1) for the next four weeks. Antigenic and cumulative scores were evaluated after this period once again. Mean liver ascorbate paralleled dietary intake and the values obtained w er e significantly different in the three groups. Blood histamine was significantly depressed in the high ascorbate group compared to the adequate and low ascorbate groups, and liver ascorbate was inversely correlated to blood histamine levels (r= -0.97, p<0.001). Although mean antigenic and cumulative scores in the low ascorbate group were lower than those of adequate and high ascorbate groups, the differences were not significant. It was concluded that ascorbate may enhance immune function through detoxifying histamine, an immunodepressor compound. However, the immunostimulatory effect of ascorbate on cell mediated immunity was not confirmed in this study. In chronic ascorbate deficiency, there may be a predisposition to infectious diseases due to depressed immune function, at least because of disturbances in metabolism of other nutrients influencing immune responsiveness, especially iron and folate. Ascorbic acid, Histamine, Delayed-type hypersensitivity, Guinea pigs. 351 354 http://mjiri.iums.ac.ir/browse.php?a_code=A-10-298-290&slc_lang=en&sid=1 M JALALI 20031947532846004279 20031947532846004279 Yes From the Department of Nutrition and Biochemistry, School of Public Health & Institute of Health Research, Tehran University of Medical Sciences, P.o.Box 14155-6446, Tehran TR NEYESTANI 20031947532846004280 20031947532846004280 No the Department of Biochemistry & Nutrition, Faculty of Medicine, Hamadan University of Medical Sciences, Hamadan, Islamic Republic of Iran SA KESHAVARZ 20031947532846004281 20031947532846004281 No From the Department of Nutrition and Biochemistry, School of Public Health & Institute of Health Research, Tehran University of Medical Sciences, P.o.Box 14155-6446, Tehran F SIASSI 20031947532846004282 20031947532846004282 No From the Department of Nutrition and Biochemistry, School of Public Health & Institute of Health Research, Tehran University of Medical Sciences, P.o.Box 14155-6446, Tehran