Deletion of fcgamma receptor IIB renders H-2(b) mice susceptible to collagen-induced arthritis

Abstract

Autoimmune diseases, like rheumatoid arthritis, result from a dysregulation of the immune response culminating in hyperactivation of effector cells leading to immune-mediated injury. To maintain an appropriate immune response and prevent the emergence of autoimmune disease, activation signals must be regulated by inhibitory pathways. Biochemical and genetic studies indicate that the type IIB low-affinity receptor for immunoglobulin (Ig)G (FcgammaRIIB) inhibits cellular activation triggered through antibody or immune complexes and may be an important component in preventing the emergence of autoimmunity. To investigate the role of FcgammaRIIB in the development of type II collagen (CII)-induced arthritis (CIA), a model for rheumatoid arthritis in humans, we have examined its contribution in determining the susceptibility to CIA in the nonpermissive H-2(b) haplotype. H-2(b) mice immunized with bovine CII do not develop appreciable disease. In contrast, immunization of the FcgammaRIIB-deficient, H-2(b) mice with bovine CII induced CIA at an incidence of 42.2%. The maximal arthritis index of the FcgammaRIIB-deficient mice developing CIA (6.9 +/- 3.6) was comparable to that of DBA/1 mice (8.6 +/- 1.9), an H-2(q) strain susceptible for CIA induction. IgG1, IgG2a, and IgG2b antibody responses against CII were elevated in the FcgammaRIIB-deficient animals, especially in those mice showing arthritis, but less pronounced than DBA/1 mice. Histological examinations of the arthritic paws from FcgammaRIIB-deficient mice revealed that cartilage was destroyed and bone was focally eroded in association with marked lymphocyte and monocyte/macrophage infiltration, very similar to the pathologic findings observed in DBA/1 mice. These results indicate that a nonpermissive H-2(b) haplotype can be rendered permissive to CIA induction through deletion of FcgammaRIIB, suggesting that FcgammaRIIB plays a critical role in suppressing the induction of CIA.

Figure 1

Development of CIA in mice by disruption of FcγRIIB expression. Incidence of arthritis (A) and severity of clinical signs (B) in FcγRIIB^−/− mice (•, n = 16), wild-type H-2^b mice of 129/B6 hybrid background (⋄, n = 13), and DBA/1 mice (□, n = 11) after immunization with CII in CFA as described in Materials and Methods. Results are expressed as a percentage of arthritic mice with the arthritic index 5 (A) and as the mean arthritic scores in each group on a given day during the course of CIA (B). Representative data from three separate experiments with similar results are shown.

Figure 2

Clinical and histologic presentation of CIA in FcγRIIB^−/− and DBA/1 mice. (A–C) The appearance of a normal forepaw from a CII-immunized wild-type mouse (A) contrasted with arthritic paws from an FcγRIIB^−/− animal (B) and a positive control DBA/1 mouse (C). (D–F) Cross-sections of the forefoot from a normal wild-type mouse (D) compared with an arthritic joint from FcγRIIB^−/− (E) and DBA/1 animals (F). Original magnifications: ×50 (D), ×80 (E), ×80 (F). D illustrates normal cartilage–bone without inflammation, whereas E and F show marked mononuclear cell infiltration with cartilage–bone destruction.

Figure 3

Concentration of anti-CII antibodies in sera from mice immunized with CII. The mean ± SD antibody levels of IgG1 (A), IgG2a (B), IgG2b (C), and IgM (D) subclasses, for all animals, and the mean ± SD of antibody levels (E–H) of arthritic DBA/1 (□) and FcγRIIB^−/− (•) mice and of nonarthritic wild-type mice (⋄) are shown. **P < 0.01.

Figure 4

Proliferation and IFN-γ production of anticollagen lymph node cells in response to CII. (A) Lymph node cells (5 × 10⁵/well) were stimulated in vitro with 5, 50, or 100 μg/ml heat-denatured CII (dCII) for 4 d. Proliferative response was determined by uptake of [³H]TdR pulsed for the final 18 h of culturing. (B) Each of the culture supernatants at the end of the experiment in A was collected and assessed for the IFN-γ content by ELISA. **P < 0.01 compared with wild-type mice.

Figure 5

Secretion of IL-1α by peritoneal macrophages stimulated with IC. Thioglycollate-elicited peritoneal macrophages from FcγRIIB^−/− (black bars) and wild-type (white bars) mice and DBA/1 mice (stippled bars) were stimulated with IgG1- opsonized SRBCs as described in Materials and Methods. The culture supernatant was analyzed for the IL-1α content by ELISA.