The effects of malnutrition on secretory and cellular immune processes.

About 15 million children under 5 years of age die each year due to suppressed immunity and the resulting increased infection. In severely malnourished children and animals some immune systems such as T-cell function, secretory IgA and complement are significantly suppressed. Other systems, such as the serum IgG or IgA, are normal or even elevated. Some of these changes are apparently caused by nutritional stress while others may be due to stimulation by increased incidence of infection and antigen load. On the other hand, marginal malnutrition stimulates increased phagocytosis and T-cell function with increased immunity to cancer but decreased resistance to certain microbial agents. The mechanisms of immune suppression by malnutrition, persistence of these effects after renutrition, and the effect of maternal malnutrition on newborn immunity are critically reviewed. Possible non-nutritional means of rapid immunological restoration of malnourished children are described.