Oral and portal venous tolerance in the interferon-γ knockout (GKO) mouse 1

Abstract

Background The role of the proinflammatory cytokine interferon-γ (IFN-γ) in the development of oral or portal venous tolerance is poorly defined. By using knockout mice for IFN-γ (GKO mice), we investigated the effect of both oral and portal venous administration of alloantigen on the systemic delayed type hypersensitivity (DTH) response to alloantigen rechallenge. Materials and methods C57BL/6 (B6) control and GKO mice (also on a B6 background) were given either saline or BALB/c spleen cells (25 million) by oral gavage (PO) or by injection into the portal vein (PV) on day 0. The injection of 10 million BALB/c spleen cells subcutaneously into the dorsal flanks was performed after 7 days followed by footpad injection of 10 million BALB/c spleen cells on day 14. Specific footpad swelling was measured 24 h later using a micrometer. Splenocyte responsiveness was measured by in vitro mixed lymphocyte culture and cytotoxic T lymphocyte assay. Cytokine production of interleukin (IL)-2, IL-4, IL-10, and IFN-γ was measured by enzyme-linked immunosorbent assay. Results Although B6 mice given PO or PV saline demonstrated a DTH response of 0.47 ± 0.04 mm and 0.49 ± 0.05 mm, respectively, in GKO mice, a greater DTH response of 0.72 ± 0.08 mm and 0.75 ± 0.05 mm was measured after either PO or PV saline ( P < 0.05, P < 0.05, respectively). In vitro MLC and CTL confirmed the heightened DTH response to BALB/c observed in GKO versus B6. Despite this heightened response in control GKO mice, the DTH response was completely suppressed in both GKO and B6 mice, after both PO and PV BALB/c feedings ( P < 0.001, P < 0.001, respectively, in both GKO and B6 mice). The unchanged brisk response to third-party C3H/HeJ demonstrated antigenic specificity. Conclusions Although DTH responsiveness to alloantigen is increased in the absence of IFN-γ, both oral and portal venous alloantigen-specific tolerance can still be established in GKO mice similar to that in control B6 mice. The achievement of a tolerogenic immune response by both oral and portal venous routes indicates that lack of IFN-γ does not preclude the induction of tolerance in this murine model.