[Repeated immune response in gnotobiotic rats].

Repeated immune response to diphtheria toxoid was investigated in monocontaminated rats. It was shown that repeated immunization of these animals led to a sufficiently intensive immune response by the secondary type, but it ended much earlier than in the usual animals (by the 12th day). A supposition is put forward that earlier termination of the secondary response in gnotobionts is caused by the absence in their lymph nodes of an additional differentiation of cell-precursors at the late periods of secondary immune response.