HAVCR2 and neoplasm: Besides, the restricted success of immunotherapy in treating most solid tumors stems from the tumor microenvironment's suppressive components, such as M2 macrophages, T regulatory cells, myeloid-derived suppressor cells (MDSCs), and inhibitory receptors including programmed cell death protein 1 (PD-1), cytotoxic T lymphocyte-associated protein-4 (CTLA-4), and T cell immunoglobulin mucin-receptor 3 (TIM-3), which all dampen systemic immune responses [[6], [7], [8], [9], [10], [11]].