Activated innate lymphoid cell populations accumulate in human tumour tissues.

BACKGROUND: Innate lymphoid cells (ILC) are part of a heterogeneous family of haematopoietic effector cells which lack re-arranged antigen-specific receptors. They promote host defense and contribute to tissue and metabolic homeostasis, wound healing and immune surveillance. Their role in human cancer immunity is less defined, and therefore we aimed to identify the frequency and phenotype of distinct ILC groups in various types of cancer. METHODS: Tissue samples and peripheral blood were collected from patients undergoing surgical resection of gastrointestinal and breast tumours. Single cell suspension of tumour tissue was immediately obtained following surgery using tumour dissociation. RESULTS: We observed significantly higher frequencies of ILC2 (p value: 0.04) in malignant breast cancer tissue and significantly higher frequencies of group 1 ILC (p value: 0.001) in malignant gastrointestinal tumours. Tumour infiltrating ILC were found to show an activated phenotype with higher expression of MHC-II, KLRG1, early activation marker CD69 and CD44. CONCLUSIONS: Activated innate lymphoid cells infiltrate tumours dependent on tumour type and location.