CD8A and neoplasm: have shown that lowering the environmental pH to values of 6.0–6.5 induced an anergic state in human and mouse tumour-specific CD8+ T cells, characterized by impaired cytotoxic activity, inhibition of cytokine production, reduced expression of the alpha chain of the IL-2R (CD25), and a diminished activation of extracellular signal-regulated kinase (ERK) and STAT5 upon T cell activation [13].