Cell-mediated immunity in nutritional imbalance.

Marked perturbations of cell-mediated immunity are observed in nutritional imbalance, both undernutrition and overnutrition. Individuals with protein-energy malnutrition show consistent impairment of cutaneous delayed hypersensitivity and a reduced number of circulating T lymphocytes. Variable changes in lymphocyte stimulation response in vitro to mitogens and antigens are seen. There is a relative increase in the number of "null" cells and high levels of leukocyte terminal deoxynucleotidyl transferase activity. These findings suggest impaired differentiation of T cell precursors, which may be the direct result of reduced thymic hormone activity. Alterations in the production of lymphokines are not consistent. Infants with intrauterine growth retardation show a marked and long-lasting deficit in cell-mediated immunity. Specific nutrient deficiencies vary in their ability to influence cell-mediated immunity and the mechanisms underlying the immunologic abnormalities. Among others, zinc and pyridoxine deficiencies are associated with marked immunodepression. Obesity also is associated with alterations in cell-mediated immune responses. This has been observed in man, in genetically obese mice, and in states of excess intake of lipids, vitamins, minerals, and a trace elements. Nutritional modulation of cellular immunity is an important determinant of morbidity in several systemic disorders.