THE ONTOGENY OF CLASS-REGULATION OF CD4(-LYMPHOCYTE POPULATIONS() T)

The differential dass-regulation of CD4(+) T lymphocyte populations is believed to play a major role in determining the qualitative behaviou r of the immune system, and in the fate of immune responses in particu lar. In this article we propose a model for the dynamics of the T(h)1 and T(h)2 subpopulations. We put forward the concept of an 'antigenic niche' which allows us to postulate that the key feature underlying th e regulation of T-h differentiation pathways is the population dynamic s of the lymphocytes themselves. Using this model we are able to accou nt for a number of established experimental observations which were hi therto apparently unrelated and poorly understood. This suggests that our simplified model might be capturing some essential features of the immune system.