Moreover, although we did not compare the differences in the secondary structure of B5 derived from recombinant Pichia pastoris and chemically synthesized B5, they both promoted the secretion of TNF-α and IL-1β in macrophages and enhanced pulmonary mucosal immunity against bacterial infections [25,26,27], and we supposed that B5-induced protection was non-specific, and B5 may be used as an adjuvant to the existing antimicrobial therapy to control multiple bacterial infections in the respiratory tract. Here, TNF is linked to bacterial infectious disease.