However, recent studies suggest that a specific gene expression profile, including elevated expression of programmed cell death protein 1 (PD-1), T-cell immunoreceptor with Ig and ITIM domains (TIGIT), and CXCL13, correlates better with the presence of reactive TCR clones and may serve as a more precise tool for isolating cells with potential anti-tumor activity. The gene discussed is PDCD1; the disease is neoplasm.