Kinetics of alkaline phosphatase active cells in the thymus of growing rabbits.

The kinetics of alkaline phosphatase active cells is followed up by quantitation in the thymus of newborn rabbits, of 1, 2, 3, 4, and 6 months old, as well as in adult ones. The proportion of these cells appears to be the lowest in newborn rabbits (2 per cent), increases up to 8 per cent in the 2-month-old and up to 15.3 per cent in the 3-month old rabbits. This maximal proportion rapidly decreases one month later, reaching values round about 1 per cent of all thymus cells in adult rabbits. This kinetics seems to reflect the process of functional maturation of the rabbit lymphoid system, the alkaline phosphatase active cells representing the thymocytes which differentiate in T cells or a subpopulation of them only.