Collagen-induced arthritis is exacerbated in IL-10-deficient mice

Abstract

IL-10 is a potent immunoregulatory cytokine attenuating a wide range of immune effector and inflammatory responses. In the present study, we assess whether endogenous levels of IL-10 function to regulate the incidence and severity of collagen-induced arthritis. DBA/1 wildtype (WT), heterozygous (IL-10+/-) and homozygous (IL-10-/-) IL-10-deficient mice were immunized with type II collagen. Development of arthritis was monitored over time, and collagen-specific cytokine production and anticollagen antibodies were assessed. Arthritis developed progressively in mice immunized with collagen, and 100% of the WT, IL-10+/-, and IL-10-/- mice were arthritic at 35 days. However, the severity of arthritis in the IL-10-/- mice was significantly greater than that in WT or IL-1+/- animals. Disease severity was associated with reduced IFN-gamma levels and a dramatic increase in CD11b-positive macrophages. Paradoxically, both the IgG1 and IgG2a anticollagen antibody responses were also significantly reduced. These data demonstrate that IL-10 is capable of controlling disease severity through a mechanism that involves IFN-gamma. Since IL-10 levels are elevated in rheumatoid arthritis synovial fluid, these findings may have relevance to rheumatoid arthritis.

Figure 1

Incidence and severity of collagen-induced arthritis (CIA) in DBA/1 wildtype (WT), IL-10^+/-, and IL-10^-/- mice. (a) Incidence of CIA, expressed as the percentage of arthritic animals in the WT (n = 17), the IL-10^+/- (n = 12), and the IL-10^-/-(n = 11) mice groups. (b) Disease severity, expressed as the cumulative arthritis score, in affected animals. Values are presented as the mean ± standard error of the mean, and represent one of two experiments. Severity of arthritis was significantly different between days 20 and 50. * P < 0.05 in comparison with WT mice.

Figure 2

Collagen-specific antibody response is reduced in IL-10^-/- mice. DBA/1 wildtype (WT) (n = 17), IL-10^+/- (n = 12) and IL-10^-/- (n = 11) mice were immunized with collagen, and the serum antibody isotypes to collagen were measured by ELISA. Values are presented as the mean ± standard error of the mean. * P < 0.05 in comparison with WT mice.

Figure 3

IFN-γ levels are reduced in IL-10^-/- mice. Spleens were harvested from collagen-immunized mice and restimulated with collagen ex vivo. Supernatants were harvested on day 5 and assayed by ELISA. Values are presented as the mean ± standard error of the mean of: (a) DBA/1 wildtype (WT) (n = 17), IL-10^+/- (n = 12), and IL-10^-/- (n = 11) mice; and (b) WT (n = 13) and IL-10^-/- (n = 7) mice. * P < 0.05 in comparison with WT mice.

Figure 4

IL-1β levels are increased in IL-10^-/- mice. Supernatants were harvested on day 5 and assayed by ELISA. Values are presented as the mean ± standard error of the mean of DBA/1 wildtype (WT) (n = 12) and IL-10^-/- (n = 7) mice, and represent one of two experiments. * P < 0.05 in comparison with WT mice. TNF-α, tumor necrosis factor alpha.