Th1 Adjuvant N-Acetyl-d-Glucosamine Polymer Up-Regulates Th1 Immunity but Down-Regulates Th2 Immunity against a Mycobacterial Protein (MPB-59) in Interleukin-10-Knockout and Wild-Type Mice

Treatment of mice with heat-killed (HK) Mycobacterium bovis BCG or 1- to 10-μm chitin particles (nonantigenic N-acetyl-d-glucosamine polymers) is known to induce innate immune responses including gamma interferon (IFN-γ) production which plays a Th1 adjuvant role. However HK BCG further induces prostaglandin E2-releasing spleen macrophages (Mφ) (PGE2-Mφ) which potentially inhibit Th1 adjuvant activities. We found that chitin particles did not induce PGE2-Mφ formation. To further assess whether chitin has Th1 adjuvant effects interleukin-10 (IL-10)-knockout (KO) mice and their wild-type (WT C57BL/6) controls were immunized with a 30-kDa MPB-59 mycobacterial protein mixed with chitin. Immunization with MPB-59 alone induced Th2 responses characterized by increases in total serum immunoglobulin E (IgE) and specific serum IgG1 levels and spleen Th2 cells producing IL-4 IL-5 and IL-10. No IFN-γ-producing spleen Th1 cells specific serum IgG2a or delayed-type hypersentivity (DTH) footpad reactions were detected. On the other hand chitin–MPB-59 immunization significantly increased spleen Th1 responses DTH reaction and serum IgG2a levels along with decreases of Th2 responses. The magnitude of these Th1 adjuvant effects was greater in IL-10-KO mice than in WT mice. In contrast immunization with HK BCG–MPB-59 showed little or no Th1 adjuvant effect. These data indicate that chitin has a unique Th1 adjuvant effect on the development of Th1 immunity against a mycobacterial antigen. IL-10 down-regulates the adjuvant effect of chitin. Originally published Infection and Immunity Vol. 69 No. 10 Oct 200