Protien-calorie malnutrition has been associated with a variety of immunologic abnormalities and maternal malnutrition has been shown to adversely affect fetal organ growth. The proposed investigations explore the hypotheses that maternal malnutrition affects the immune status of the infant and that maternal secretory immunity is affected by malnutrition. Maternal nutritional status will be evauated by history, anthropometry, including skin-fold compressibility, and biochemically, including urea nitrogen/creatinine ratios. Infant immune status will be assessed by measuring E-rosette formation, lymphocyte response to PHA, serum and salivary immunoglobulins, complement, antibody response and skin testing. Maternal secretory immunity will be assessed by measuring milk levels of complement, immunoglobulins, and lysozyme, and salivary and milk antibody response to antigenic stimulation with oral Streptococcus mutans, and intestinal Salmonella enteritidis. The protective effects of maternal milk antibody activity will be observed in infants exposed to an environmental pathogen (Salmonella enteritidis) prior to breast feeding.