Developmental aspects of cell-mediated immunity and findings in low birth weight infants

Abstract

The development and maturation of immunity is a series of timed steps beginning with the epithelial outgrowth of the thymus from the third branchial pouch. Lymphoid cells, probably of extrathymic origin, populate the anlagen around the 6th week gestation. This is followed by the ability to respond to allogenic cells and later on to mitogens. The acquisition of surface markers occurs around the 10–11th week gestation. In the newborn, the absolute number of T cells is comparable to that in older children. However, the ability to mount delayed hypersensitivity reactions is impaired. The synthesis of some lymphokines is normal whereas that of others is reduced. Fetal growth retardation due to variety of causes can result in severe deficits in cell-mediated immunity of the newborn. This impairment may persist for several months to years, despite adequate nutrient intake in postnatal life. Infection, maternal ingestion of drugs and many other factors can affect the normal development of the immune system.