Fig. 1.

Kinetics of expression of CD45RA and CD45RO antigens on newborn and adult T cells during prolonged phytohaemagglutinin (PHA) and anti-CD2 MoAb activation. Adult (•, n = 7) and newborn (□, n = 6) CD4⁺CD45RA⁺ T cells (1 × 10⁶ cells/ml) were co-cultured with PHA plus 2% accessory cells (a,b,c) or anti-CD2 MoAbs plus 4% accessory cells (d,e,f), and cultures were propagated in IL-2. On specified days, cell aliquots were removed, washed thoroughly, and double-stained with FITC-labelled anti-CD45RA MoAbs and PE-labelled anti-CD45RO MoAbs (Dakopatts, High Wycombe, UK). Flow cytometric analysis was performed on a Becton Dickinson FACScan. Data are presented as the average percentage (+ 1 s.d.) of cells which were CD45RA⁺RO⁻ (a,d), CD45RA⁺RO⁺ (b,e), or CD45RA⁻RO⁺ (c,f) at a given time point. *P < 0.05 compared with adult values.