Challenging the assumption of exponential decay. A review on the life expectancy of T-cells.

Abstract

Mathematical models are a common tool used to describe and understand the kinetics of immune cells. However, these models often make certain assumptions in order to describe a simplified view of reality. In this review we take a closer look at the assumption of exponential cell loss. Exponential cell loss assumes that the loss rate of a cell is defined by a single, fixed, parameter. However, this results in a random, fixed, chance for a cell to die irrespective of its life history. In this review we aim to challenge this assumption, and give an overview of how T-cell loss rates have been observed to dynamically change throughout a cell’s lifespan. Additionally, we will discuss several model implementations that avoid the assumption of exponential cell loss, and show how these models use mechanisms of individual cell based adaptation or population based selection to give a better description of T-cell kinetics.