Thymus-dependent lymphocytes and delayed hypersensitivity in low birth weight infants.

The proportion of thymus-dependent (T) lymphocytes in the blood and the ability to mount cutaneous delayed hypersensitivity to a battery of antigens were evaluated in 50 low birth weight (LBW) infants when they were 3 months to 5 years old. There was a significant reduction in the number of T lymphocytes. Delayed hypersensitivity was impaired. The abnormalities were more pronounced in those with persistent growth retardation. It is suggested that continued postnatal depression of cell-mediated immunity in LBW infants may contribute to increased frequency of infections and immunopathological diseases.