Deficient quantitative expression of CD45 isoforms on CD4+ and CD8+ T cell subpopulations and subsets of CD45RA^lowCD45RO^low T cells in newborn blood

Deficiencies in the quantitative expression of CD45RA and CD45RO on CD4+ and CD8+ T cells and in a population of CD45RA^lowCD45RO^low T cells in blood from term newborn infants were found by flow cytometry. The relative frequencies of CD45RO on CD4+ T cells from adults and newborn infants were 72 and 58%, respectively. However, in newborn infants greater than 70% of T cells expressing CD45RO also expressed CD45RA. In addition, the quantitative expression of CD45RA and CD45RO on newborn T cells was significantly less than that found on adult blood T cells.