Neonatal thymectomy and the decrease in antigen-sensitivity of the primary response and immunological "memory" systems

Neonatal thymectomy of Swiss mice induced a 100-fold increase in antigen-dose needed to elicit a primary haemolysin response to sheep erythrocytes and a ten-fold increase in antigen-dose needed to elicit immunological `priming', when the mice were tested for antigen-sensitivity at 6 weeks of age. Using different antigen systems, other laboratories have reported that thymectomized mice exhibited a normal primary response and a ten-fold reduction in the level of antibody reached in the secondary response. It is suggested that the varying effect of thymectomy on the primary response is attributable to variations in the time of development of the capacity to give a primary antibody response against the different antigens.