ICOS and colorectal carcinoma: Following activation, follicular T cells upregulate activation markers, such as the co-inhibitory receptor programmed cell death 1 (PD1), inducible T-cell co-stimulator (ICOS), and CD38, express signature transcription factors, such as B cell lymphoma 6 (BCL-6) and increased IL-21 and IL-10 production, which can support their role as immune mediators in CRC [23].