CXCL8 and coinfection: Notably, zfhnf4α knockout exerted context-dependent effects: in A. salmonicida single infection, it significantly upregulated ifn3, il-8, and il-17 but downregulated il-1β relative to wild-type; in GCRV-II single infection, knockout did not affect ifn1, ifn3, or il-1β but enhanced il-8, il-17, and tnfα expression; and in co-infection, knockout upregulated ifn3 and all tested pro-inflammatory cytokines (il-8, il-1β, il-17, tnfα).