CD4 and bacterial infectious disease: The results indicated that compared with control group, rtOmpF significantly enhanced the expression of immune-related genes involved in inflammatory response (IL-1β1, TNF-α), humoral immunity (MHC II β and CD4-L2) and cellular immunity (MHC Iα, CD8α, and IFN-γ) in the head kidney and spleen, especially co-injection of rtOmpF+ISA763, implying rtOmpF had potential as the antigen to induce a series of immune responses for channel catfish against bacterial infection, and ISA763 as the adjuvant improved the immune response.