Life and death as a T lymphocyte: from immune protection to HIV pathogenesis

Abstract

Detailed analysis of T cell dynamics in humans is challenging and mouse models can be important tools for characterizing T cell dynamic processes. In a paper just published in Journal of Biology, Marques et al. suggest that a mouse model with its activated CD4(+) T cells are deleted has relevance for HIV infection.

Figure 1

Schematic diagram of T cell dynamics in normal mice. The width of the arrows denotes the rate of death and division or of transit from one pool to another. Naïve T cells are T cells that have matured and left the thymus where they are generated, but have not yet encountered antigen. RTEs, recent thymic emigrants; Ag, antigen.

Figure 2

The major subsets of CD4⁺ T cells that differentiate from naïve circulating cells. Naïve T cells differentiate into at least four functional subsets following stimulation by antigen presented by dendritic cells, which are specialized for driving the activation of T cells and are thought to help direct their differentiation by differential secretion of cytokines determining the different subsets. Three subsets - T_H1, T_H2 and T_H17-activate other immune cells with distinct roles in immunity, including B cells, which secrete antibody, natural killer (NK) cells, which are important in defense against viruses, and inflammatory cells, such as neutrophils and macrophages (which also have non-inflammatory functions). The fourth subset shown here comprises regulatory T cells (Tregs), which suppress the activation of the other subsets, partly by acting on dendritic cells. Modified from Figure 5-22 in DeFranco AL, Locksley RM, Robertson M: Immunity: The Immune Response in Infectious and Inflammatory Disease. London: New Science Press; 2007.

Figure 3

Schematic diagram of dynamic changes in T cell compartments described in OX40-DTA mice [1]. The width of the arrows denotes the rate of death and division or of transit from one pool to another. RTEs, recent thymic emigrants.