Alkaline ribonuclease activity in lymphoid organs of mice after injection of tumor cells

Mice were inoculated with viable syngeneic sarcoma or with normal muscle cells, and the changes in alkaline ribonuclease activity (pH 8) in host thymus, lymph nodes, and muscle were measured. Changes in thymus weight were also measured. Ribonuclease activity was six times higher in thymus on day 2, and five times higher on day 3 after inoculation of tumor cells. In mesenteric lymph nodes, the increase in ribonuclease was about three times higher on days 3 and 5 than the control values; on day 9, the activity was less than half the control level; and during the rest of the experimental period enzyme activity was normal. In mice injected with tumor cells, thymus weight decreased between days 2 and 9, and returned to normal on day 15. Mice inoculated with normal muscle cells show no changes in ribonuclease activity and in thymus weight.