This investigation will investigate the influence of maternal diets during gestation and during lactation on the capacity of the offspring to resist infectious disease later in life. Specifically, diets marginal in lipotropes (choline and methionine) and diets marginal in protein will be fed to mother rats during gestation; at birth some will be switched from control to deprived regimens and vice versa. Some from each group of animals will be examined for development of the thymolymphatic system and both humoral and cell mediated immunity will be evaluated. Challenge with Salmonella typhimurium when 100 days of age will correlate clinical response with in vivo and in vitro techniques for immunocompetence.