CD8A and neoplasm: Lactate, along with the adenosine buildup coordinated by hypoxia via the CD39/CD73 pathway, has a direct effect of inhibiting the cytotoxic activity and proliferation of CD8+ T cells and natural killer (NK) cells and promoting the growth and polarisation of immunosuppressive cell types such as regulatory T cells (Tregs) and M2-polarised tumour-associated macrophages [229,234].