CXCR3 and viral infectious disease: Using fluorescently labeled cells, it has been shown that initial interactions between antigen-specific T and B cells during murine viral infections occur in the interfollicular zone where the CXCR3 ligands CXCL9 and CXCL10 are found (38, –, 40), suggesting that CXCR3+ Tfh are involved in the initiation of the GC response (22, 37).