Dietary Amino Acids and Immune Response in Rats

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Abstract
Young growing rats and protein-deficient adult rats were fed isonitrogenous diets varying in amino acid composition. Diets contained nitrogen from soy alpha-protein, wheat gluten, corn or a mixture of corn and acid-hydrolyzed casein, with or without supplements of the limiting amino acids. Antibodies to sheep erythrocytes were measured between 4 and 21 days after immunization. When added to diets containing corn or corn with acid-hydrolyzed casein, tryptophan increased hemolysin titers of adults and 19S (IgM) agglutinin titers in young rats 6 days after injection of antigen. The 7S (IgG) antibody on days 7 to 21 was elevated in young rats fed the corn-casein mixture if tryptophan was also fed. Addition of methionine to soy protein improved weight gains, but antibody synthesis was depressed in late primary response; the possible relationship of this depression to tryptophan status is discussed. Lysine exerted no significant effect on antibody titers. Weight, total number of cells and RNA of the spleen paralleled body weight.