CXCR5 shares 40% amino acid homology with CXCR1, so when CXCL13 activates CXCR5, this signaling axis can lead to intracellular calcium ion influx and induce the activation of several intracellular signaling cascades, such as PI3K/AKT, MAPK/ERK, and Rac pathways, playing a role in immune disorders as well as tumor progression.384, 386. The gene discussed is CXCR5; the disease is immune system disorder.