CXCL13 and rheumatoid arthritis: The presence of a B cell-helper T cell population in RA synovium with a CXCR5− Bcl6low but CCR2+ Blimp1+ phenotype illustrates that IL-21, CXCL13, and B cell help can be provided by T cell populations that differ substantially in phenotype from Tfh cells (Figure 1).