Cell surface sialic acids have been long perceived as a potential marker of “self‐associated molecular pattern (SAMP)” recognized by intrinsic inhibitory receptors in immune systems.[49] In tumor microenvironment, cancer cells take advantage of this molecular pattern by engaging Siglecs on a variety of immune cells, constituting “glyco‐immune checkpoints”.[15] However, this type of Siglec‐based glyco‐immune checkpoint receptor differs from more classical checkpoint receptors, such as PD‐1 and CTLA‐4, in lack of a defined counter receptor. The gene discussed is CTLA4; the disease is cancer.