To identify IAV- and IBV-cross-reactive HA Abs, we cultured individual HA-binding IgG+ memory B (Bmem) cells sorted from peripheral blood mononuclear cells (PBMCs) of eight human donors before or 1 to 2 wk after seasonal influenza vaccination (SI Appendix, Fig. S1A) (10, 23). Here, DDX41 is linked to influenza.