PD-1hiCXCR5−CD4+ TFH Cells Play Defense in Cancer and Offense in Arthritis

T follicular helper (TFH) cells are characteristically defined by their CXCR5 positivity and homing to B cell follicles in secondary lymphoid organs (SLO). An expanded subpopulation of functionally comparable and phenotypically similar PD-1hiCXCR5−CD4+ T cells were recently identified in breast cancer (BC) and rheumatoid arthritis (RA) to have beneficial or detrimental roles, respectively, but are they inflammatory tissue effector TFH cells?SCOPUS: sh.j