Homeostatic proliferation of mature T cells

Under normal circumstances, the secondary lymphoid tissues contain a predictable number of T cells with a diverse T cell receptor (TCR) repertoire. Such a T cell pool must be of sufficient size to confer maximum protection of the host from infectious pathogens and cancer, but small enough not to overburden the host. The T cell pool is maintained by a combination of de novo T cell production by the thymus and by the long-term survival and gradual turnover of mature T cells in the periphery. The latter process, termed homeostatic proliferation, has been intensely investigated over the past 20 years, and a few techniques have been developed to facilitate these studies. In this chapter, we describe the experimental procedures that allow conspicuous visualization of homeostatic proliferation, which have been instrumental in facilitating recent advances in the study of T cell homeostasis.