Modeling the lifespan of human T lymphocyte subsets

T lymphocytes may be classified as naive or memory cells, depending on whether they possess immunological memory. The central tenet of this work is that memory lymphocytes revert to naive lymphocytes in vivo. This phenomenon is modeled by a mechanism qualitatively similar to Demoivre's law of human mortality. Additionally, both lymphocyte subsets undergo decay. Model parameters and their standard errors are estimated by maximizing a likelihood function constructed by Kalman filtering of the experimental data on the assumption that it is contaminated by measurement noise of constant relative error.