# Circulating Tumor Reactive KIR+CD8+ T cells Suppress Anti-Tumor Immunity in Patients with Melanoma

## TL;DR

A specific type of CD8+ T cell in melanoma patients suppresses anti-tumor immunity and is linked to worse survival.

## Contribution

Discovery of tumor antigen-specific KIR+CD8+ T cells with regulatory function that suppress anti-tumor immunity.

## Key findings

- Tumor antigen-specific KIR+CD8+ T cells are detectable in both tumor and blood of melanoma patients.
- Higher levels of these KIR+CD8+ T cells correlate with worse overall survival in patients.
- These cells resemble regulatory T cells and suppress anti-tumor immunity.

## Abstract

Effective anti-tumor immunity is largely driven by cytotoxic CD8+ T cells that can specifically recognize tumor antigens. However, the factors which ultimately dictate successful tumor rejection remain poorly understood. Here we identify a subpopulation of CD8+ T cells which are tumor antigen-specific in patients with melanoma but resemble KIR+CD8+ T cells with a regulatory function (Tregs). These tumor antigen-specific KIR+CD8+ T cells are detectable in both the tumor and the blood, and higher levels of this population are associated with worse overall survival. Our findings therefore suggest that KIR+CD8+ Tregs are tumor antigen-specific but uniquely suppress anti-tumor immunity in patients with melanoma.