# Cytotoxic CD4+ T cells: origin, biological functions, diseases and therapeutic targets

## TL;DR

This review explores cytotoxic CD4+ T cells, their unique functions in immune responses, roles in various diseases, and potential as therapeutic targets.

## Contribution

The paper provides a comprehensive synthesis of recent findings on cytotoxic CD4+ T cells, emphasizing their roles in disease and therapeutic potential.

## Key findings

- Cytotoxic CD4+ T cells exhibit cytotoxicity similar to CD8+ T cells, showing functional plasticity.
- These cells contribute to disease progression in cancer, infections, autoimmunity, and cardiovascular conditions.
- The paper summarizes therapeutic strategies targeting cytotoxic CD4+ T cells and clinical trial data.

## Abstract

Cytotoxic CD4+ T lymphocytes are a unique subset of CD4+ T cells characterized by their cytokine secretion and cytolytic activity. Unlike traditional CD4+ helper T cells, cytotoxic CD4+ T lymphocytes exhibit similar cytotoxicity to that of CD8+ T cells, revealing unexpected plasticity in CD4+ T-cell functions. This flexibility suggests that CD4+ T cells can transform and acquire effector functions beyond their conventional functions, emphasizing their importance in various immune responses. Despite the identification of cytotoxic CD4+ T lymphocytes decades ago, recent advancements have broadened our understanding of their phenotypic diversity, transcriptional regulation, differentiation pathways, and functional roles. Cytotoxic CD4+ T lymphocytes play pivotal roles across a broad spectrum of diseases, including cancer, infectious diseases, autoimmune disorders, and cardiovascular diseases. They typically mediate strong inflammatory responses and kill target cells through cytotoxicity, playing a crucial role in maintaining immune homeostasis. In this review, we synthesize current findings on cytotoxic CD4+ T lymphocytes, emphasizing their origin, biomarkers, regulatory molecules, and biological functions. Additionally, we focus on their pathological roles in the progression of various diseases and examine how cytotoxic CD4+ T lymphocytes contribute to disease development and progression. We also provide a comprehensive summary of therapeutic strategies targeting cytotoxic CD4+ T cells and review the associated clinical trial data, aiming to propose new strategies for disease management through the targeting of cytotoxic CD4+ T lymphocytes.