Effects of edible mushrooms on plasma levels of anti‐bovine collagen II IgG antibodies in DBA1 mice with collagen‐induced arthritis

Collagen‐induced arthritis (CIA) in mice is commonly used to study rheumatoid arthritis (RA) biology. Plasma levels of anti‐collagen II antibodies (antiCIIA) are usually elevated in CIA and RA patients. While blockade of anti‐CIIA prevents CIA, antiCIIA injection promotes it. We previously reported that 5% dry shiitake (SM) and white button (WBM) mushrooms reduced CIA incidence and severity in DBA1 mice. The current study was conducted to assess the role of antiCII IgG in reduced CIA severity in mice fed mushroom‐fortified diets. Plasma antiCII IgG and cytokines were measured by ELISA in mice fed either the AIN76 diet or the same diet fortified with 5% WBM, SM, and portabella (PM) (n = 6–8) for 6 weeks, and immunized with 100 μg bovine CII, followed by 50 μg LPS on d 21, and euthanized on d 31 post‐CII. In mice with CIA index ≥ 3, mushrooms slightly reduced plasma antiCII IgG (14% SM [p <0.05], 10% WBM, 6% PM) compared to those fed the AIN76 diet. Within the same dietary treatment group, plasma antiCII IgG levels were not different between immunized mice without and those with swollen paws. While WBM and SM decreased sICAM1 and TNF‐α by 15–53% and increased IL‐6 levels by 1.6–3fold (p <0.05), PM only had minor effects. CIA index was positively associated with antiCII IgG and IL‐6 (p<0.01) but not TNF‐α levels. Data suggest that mushrooms very likely modulate CIA through IL‐6 but not antiCII IgG; but an effect on IgG isotypes cannot be ruled out. Supported by the Mushroom Council/USDA Grant 580790706 and funds from Oklahoma State University