CXCR5 and secondary progressive multiple sclerosis: Since preliminary experiments (data not shown) indicated some circulating CD4+CXCR5+FOXP3+ cells in lumbar punctures, i.e., the CSF of living SPMS patients, it is possible that such TFR cells lose FOXP3 expression—becoming ex-TFRs—and their suppressive capacity when homing to eLFs.