Estimation of PFC and serum haemolysin response to SRBC in 'nude' mice.

The time course of the primary haemolysin response of thymusless `nude' mice to sheep red blood cells differs from that of intact animals in one main respect. After the initial peak, which is reached 4–6 days from injection of the cells, haemolysin level falls to zero at about Day 10; and there is a concurrent decline of the counts of plaque-forming cells. The prolonged phase of slow decline of haemolysin level, reflecting the production of 7S antibodies and typical of the response of normal animals, is absent. It is concluded that production of 7S haemolysins is thymus-dependent, whilst that of 19S haemolysins is thymus-independent.