Response to phytohaemagglutinin of lymphocytes from mice treated with anti-lymphocyte globulin.

Thymus, spleen, lymph node and peripheral blood lymphocytes taken from mice treated with anti-lymphocyte globulin (ALG) showed a greatly diminished response to PHA . Recovery of circulating lymphocyte levels preceded recovery of responsiveness to PHA. The latter could be prevented by reinjection of ALG or by thymectomy. Grafts were rejected within a period equal to the normal rejection time after PHA responsiveness had recovered to a value of approximately 20 per cent of the normal. Thus the effect of ALG on thymus dependent lymphocytes in mice can be monitored by assessing the PHA sensitivity of peripheral white blood cells.