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 ado lescence and even into adult life. These age-dependent changes within the immune system greatly complicate any attempt to assess pathologica l alterations of immunologic variables in children. The need for studi es on possible substance-induced changes, including risk assessment of environmental chemicals, has increased the necessity to establish ref erence ranges for certain immunologic variables against which an abnor mal developmental status can be evaluated. In the present study age-re lated changes of surface receptors on peripheral white blood cells wer e studied in 82 children, aged between 2 months and 17 years. The bloo d samples were triple labeled with monoclonal antibodies followed by a whole blood lysis technique and were subsequently analyzed by flow cy tometry. Complex statistical analyses were performed in order to deter mine probability ranges for some immunological variables. In this pape r we describe the age-dependent development of components involved in major maturational processes, including the appearance and varying exp ression of adhesion receptors (CD11a, CD18, CD28, CD29, CD44, CD49d an d CD54) on CD4(+) ''helper'' cells and CD8(+) ''suppressor and cytotox ic'' cells. A clearcut 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 largel y acquired during postnatal development. Maximal levels of adhesion re ceptor expression are reached at different ages depending on the speci fic T cell subpopulation.