CXCL13

CXCL13, or BLC (B-lymphocyte chemoattractant, mouse equivalent of human B cell-attracting chemokine-1), is a 12 kDa an ELR-CXC chemokine. CXCL13 is the ligand for CXCR5. As such, CXCL13 is a chemoattractant for primary B-cells and T follicular helper cells (TFH). It is thought that the increased CXCL13 provides selection signals to both germinal center B cells and TFH cells (see TFH cells in the TFH section). Concomitant with decreased CCR7 expression that is greatly reduced in TFH cells, there is loss of responsiveness to the chemokines CCL19 and CCL21. This further helps enhance the migration of TFH cells toward the CXCL13-rich areas increasing the probability of antigen-specific contact between the specific TH cells and the antigen primed B cells. This allows for TFH cells homing to regions rich in CXCL13 such as follicular regions and remove the promotion the extrafollicular placement due to CCL19 and CCL21-rich areas in the lymphoid tissue. CXCL13 may also be a good diagnostic biomarker for prostate cancer and its advancement, but futher studies are need to further prove/disprove this correlation.