Development of T Cells with Memory Phenotype in Infancy

Abstract

Studies in mice give a reasonably clear view of the genes in he germline which are rearranged to give the αβ heterodimer of the T cell receptor for antigen. The role of the thymus in modulating the germline repertoire through positive and negative selection has been demonstrated in transgenic mice¹ and in the context of the mixed lymphocyte stimulatory (MIs) antigens, which result in the deletion of entire families T cells using certain β chain families for their V regions². Comparable T cell selection events are likely to occur during the production of thymus cells in human infants. It is T cell maturation in he thymus which provides the fetus and newborn with a clonally diverse population of naive T cells which is available for a response to an environmental antigen. T cell responses to antigen are characterized by proliferation (synonymous with clonal expansion) and the production of memory T cells. The recognition that human T cells express different isoforms of the T200 common leukocyte antigen (CD45) depending on their prior proliferative responses has made the process by which the naive T cell pool is educated by antigen open to examination³.