CD45RA expression of gamma delta and alpha beta T cells emigrating from the fetal and postnatal thymus

We have compared the expression of CD45RA on alpha beta and gamma delta T cells emigrating from the fetal and postnatal thymus. The fetal and postnatal thymus export both CD45RA+ and CD45RA- T cells. The number of gamma delta +CD45RA+ T cells was remarkably constant regardless of stage of ontogeny or T cell maturity. Around 5-8% of gamma delta thymic emigrants, thymocytes and peripheral blood lymphocytes expressed CD45RA in both fetal and postnatal animals. In contrast to gamma delta T cells, up to one quarter of both fetal and postnatal alpha beta emigrants expressed CD45RA. Post-thymic maturation of CD45RA expression of alpha beta emigrants, which occurred both before and after birth, appeared to be antigen independent.