Reduced expression of the interleukin-2-receptor gamma chain on cord blood lymphocytes: relationship to functional immaturity of the neonatal immune response.

Mutation of the interleukin-2 (IL-2) receptor gamma chain, which also serves as a component of the receptor complexes for IL-4, 7, 9 and 15, results in severe immune deficiency. We hypothesized that the immunological immaturity of healthy neonates might be associated with low levels of expression of this receptor molecule. Using monoclonal antibody and a highly sensitive immunofluorescence method, we showed that IL-2 receptor gamma chain is expressed at significantly lower levels on cord blood cells compared with adult cells. IL-2-dependent T-cell activation in vitro was reduced in cord blood cells compared with adult cells, but B-cell responses to IL-4 were not obviously impaired. The lower level of expression of the gamma chain and some other cytokine receptor chains may contribute to the immunological immaturity of the newborn, by selectively depressing particular immunological mechanisms.