A mathematical study of CD8+ T cell responses calibrated with human data

TL;DR

This study employs mathematical modeling and Bayesian inference to analyze human CD8+ T cell responses, revealing that increased clonotypes reduce differentiation divisions, supporting the decreasing potential hypothesis over the increasing potential scenario.

Contribution

It introduces a deterministic mathematical model calibrated with human data to elucidate CD8+ T cell dynamics across compartments, supporting the decreasing potential differentiation hypothesis.

Findings

Decreasing potential hypothesis better fits vaccine data.

More clonotypes lead to fewer divisions for differentiation.

Model integrates lymph node, blood, and skin compartments.

Abstract

Complete understanding of the mechanisms regulating the proliferation and differentiation that takes place during human immune CD8+ T cell responses is still lacking. Human clinical data is usually limited to blood cell counts, yet the initiation of these responses occurs in the draining lymph nodes; antigen-specific effector and memory CD8+ T cells generated in the lymph nodes migrate to those tissues where they are required. We use approximate Bayesian computation with deterministic mathematical models of CD8+ T cell populations (naive, central memory, effector memory and effector) and yellow fever virus vaccine data to infer the dynamics of these CD8+ T cell populations in three spatial compartments: draining lymph nodes, circulation and skin. We have made use of the literature to obtain rates of division and death for human CD8+ T cell population subsets and thymic export rates. Under the decreasing potential hypothesis for differentiation during an immune response, we find that, as the number of T cell clonotypes driven to an immune response increases, there is a reduction in the number of divisions required to differentiate from a naive to an effector CD8+ T cell, supporting the "division of labour" hypothesis observed in murine studies. We have also considered the reverse differentiation scenario, the increasing potential hypothesis. The decreasing potential model is better supported by the yellow fever virus vaccine data.