# CD8+ T cells against extracellular pathogens: more than just a cytotoxic cell

## TL;DR

This review explores how CD8+ T cells influence immune responses and outcomes in infections caused by extracellular pathogens.

## Contribution

The paper highlights the regulatory and cytokine-mediated roles of CD8+ T cells in extracellular infections, beyond their traditional cytotoxic function.

## Key findings

- CD8+ T cells modulate immune responses by secreting cytokines like IFNγ during extracellular infections.
- CD8+ T cells can eliminate antigen-presenting cells to restrict immunopathology.
- IFNγ from CD8+ T cells may collaborate with IL-17 to combat extracellular pathogens.

## Abstract

The role of CD8+ T cells, as cytotoxic cells, being critical against intracellular pathogens is well known. Through the killing of infected (target) cells, CD8+ T cells impair intracellular pathogens' replication. However, extracellular pathogens are not directly targeted by CD8+ T cells, since these pathogens do not express MHC‐I‐peptides, responsible for the activation of the cytotoxic activity of CD8+ T cells. In this sense, how CD8+ T cells affect the course of extracellular infections is discussed in this review, underscoring the important regulatory functions of CD8+ T cells, killing phagocytes and other cells that are able to cross‐present extracellular antigens. In addition, the role of CD8+ T cells in the modulation of immune responses through the secretion of cytokines, such as gamma interferon (IFNγ), is also discussed in the context of extracellular infections.

CD8+ T cells can induce immunopathology or disease tolerance and resistance in infections caused by extracellular pathogens. The secretion of IFNγ by CD8+ T cells can collaborate with IL‐17 for the elimination of extracellular pathogens. In addition, CD8+ T cells can restrict immunopathology through the elimination of APCs.