The high potential and feasibility of monitoring circulating CXCL13/CXCR5-associated effectors has already been illustrated by Herati et al., who demonstrated an increase in circulating Tfh and B cells and CXCL13 serum levels in response to influenza vaccination in a subset of anti-PD-1 treated patients [72]. This evidence concerns the gene CXCL13 and influenza.