CD4 and follicular lymphoma: Varying levels of PD-1 expression on follicular lymphoma cells reflect on the Tfh phenotype of intratumoral CD4+PD-1high T cells with no TIM3 expression that supports B cell growth, while CD4+PD-1low T cells elicit an exhausted phenotype, express TIM3 with reduced cytokine secretion and cellular signaling, and significantly correlate with a reduced overall survival in follicular lymphoma patients (193).