CD4 and neoplasm: In addition, RT can upregulate the level of immune checkpoint molecules, including PD-L1 on tumor cells [10], TIM3 on CD4+ [43], CD8+ T cells, and Tregs [44], as well as T cell immunoreceptor with Ig and ITIM domains (TIGIT) on CD8+ T cells, natural killer (NK) cells, Tregs, and T follicular helper cells [45], which effectively dampens antitumor activity.