CCL27 and neoplasm: Although we did not observe differences in the expression of CTLA-4 and PD-1 on ILC populations in malignant and benign breast tumour tissue (Fig. 2a, and Additional file 1: Figure S2 and Additional file 1: Figure S3), the level of PD-1 was significantly upregulated in tumour associated ILC2 (p value: 0.04) and NK cells (p value: 0.02) compared to circulating ILC in peripheral blood (Fig. 2a).