PDCD1 and digestive system neoplasm: Interestingly, we observed higher expression of PD-1 on ILC2 (p value: 0.03) and ILC3 (p value: 0.04) populations in GI tumours compared to para lesional tissue, while CTLA-4 was not significantly altered (Fig. 2b and Additional file 1: Figure S4 and Additional file 1: Figure.