We examined the developmental profile of TCR-γ/δ+ cells with respect to CD45RO expression. Although total TCR-γ/δ+ cells were negligible in the neonatal blood and increased with advancing age, most blood TCR-γ/δ+ cells markedly expressed CD45RO without a distinction of age, probably reflecting a different CD45RO expression of two subsets defined by BB3 and δTCS1 mAbs. The vast majority of BB3+ cells expressed CD45RO, whereas expression of CD45RO was virtually absent in the δTCS1+ population. Functional studies revealed that, while both TCR-γ/δ+ cell subsets showed CD3-mediated activation, only BB3+ (or TiγA+) cells, but not δTCS1+ cells, appeared to proliferate in response to PPD in PPD-reactive individuals. The results suggested that the CD45RO+ (BB3+ or TiγA+) subset among blood TCR-γ/δ+ cells may be mainly involved in the memory or primed component of the immune system responding to some foreign antigens.
Differential expression of CD45RO (UCHL1) and its functional relevance in two subpopulations of circulating TCR-γ/δ+ lymphocytes
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