Macrophage
Large immune cells that engulf and digest debris, microbes and dead cells and coordinate inflammation. Tumours recruit and retrain them, so in many cancers macrophages end up helping the tumour rather than fighting it.
Macrophages can be pro-inflammatory and tumour-killing or tissue-repairing and immunosuppressive, and tumours push them towards the latter; tumour-associated macrophages can make up half the cells in some tumours, where they promote blood-vessel growth, suppress T cells, help cancer cells invade, and take up ADC payloads that contribute to side effects. Cancer cells display CD47, a 'don't eat me' signal, to stop macrophages engulfing them, and CD47 blockers are in trials. Efforts to reprogramme macrophages (CSF1R inhibitors, CD40 agonists, CAR-macrophages) have been harder to translate than T-cell approaches.