CXCL12 and renal cell carcinoma: Recent studies have shown that infiltration of CD8+ T cells with high CXCL13 expression in RCC results in an immunosuppressive microenvironment.257 Apart from CXCL13, stromal cells secrete CXCL12, which is also shown to promote B lymphoid follicle formation in the absence of FDCs.222 CXCL12/CXCR4 and CXCL13/CXCR5 mediate the migration of B cells between the dark zone (DZ) and light zone (LZ) in the GC.