CD8A and neoplasm: The parameter distributions suggest that deactivation of TILs primarily occurs through a negative feedback mechanism (log ratio a4/a5 = −3.2 ± 1.4), although very few CD8+ T cells that enter the tumor microenvironment become deactivated (P((a4 + a5)/(kp3a + kd5a + a4 + a5) > 0.5) < 0.1).