Evaluation of the age-dependent development of lymphocyte surface receptors in children.

Components and functions of the immune system change during postnatal development, not only in the first years of life, but well through adolescence and even into adult life. These age-dependent changes within the immune system greatly complicate any attempt to assess pathological alterations of immunologic variables in children. The need for studies on possible substance-induced changes, including risk assessment of environmental chemicals, has increased the necessity to establish reference ranges for certain immunologic variables against which an abnormal developmental status can be evaluated. In the present study age-related changes of surface receptors on peripheral white blood cells were studied in 82 children, aged between 2 months and 17 years. The blood samples were triple labeled with monoclonal antibodies followed by a whole blood lysis technique and were subsequently analyzed by flow cytometry. Complex statistical analyses were performed in order to determine probability ranges for some immunological variables. In this paper we describe the age-dependent development of components involved in major maturational processes, including the appearance and varying expression of adhesion receptors (CD11a, CD18, CD28, CD29, CD44, CD49d and CD54) on CD4+ "helper" cells and CD8+ "suppressor and cytotoxic" cells. A clear-cut increase of high epitope density expression of the integrins on both CD4+ and CD8+ cells was noted. These results suggest that the components of immune T cells for performing adhesion by interacting with other cells and many matrix components are largely acquired during postnatal development. Maximal levels of adhesion receptor expression are reached at different ages depending on the specific T cell subpopulation.