Ding Q, et al. – Researchers want to detect if T cell Ig and mucin domain-containing molecule (TIM)–4 identifies IFN–{gamma}–expressing proinflammatory B effector 1 cells that promote tumor and allograft rejection. They notice that TIM–4+ B cells are enriched for IFN–γ–producing proinflammatory Be1 cells. It enhances immune responsiveness and can be specifically targeted with anti–TIM–4.