Postnatal changes of CD45 expression in peripheral blood T and B cells.

One known postnatal change of CD45 expression is the decline of the CD45RAhigh CD45ROlow T subsets and the reciprocal increase of the CD45RAlow CD45ROhigh T subsets in the peripheral blood. Using a panel of monoclonal antibodies reactive with either protein or carbohydrate epitopes on the variable regions of CD45, we were able to detect more postnatal changes of CD45 expression. These changes are largely caused by modulation of the CD45 glycosylation, including: (1) lesser sialylation of the CD45RA region on T cells, and (2) differential sialylation of the CD45RB region leading to the distinction of CD45RBhigh and CD45RBlow T and B subsets. In addition, the existence of the CD45RAdim CD45ROdim labelled as transitional T cells is only found during the postnatal life. These changes may reflect the maturation of the immune system.