Figure 6.

Sialylated collagen type II (Col II)-reactive monoclonal IgG antibodies (Abs) reduce the accumulation of proinflammatory Th17 cells and IgG autoAbs. Collagen-induced arthritis (CIA) was induced in Fcgr2b^−/− mice as described in Figure 5 and Figure S5C in Supplementary Material. One day before and 9 days after the first immunization, the mice received 100 µg of either low-sialylated (low-sial; n = 10) or in vitro galactosylated plus sialylated (+sial; n = 9) anti-Col II murine IgG1 Abs (clones M2139 and CII 1–5; 50 µg each) or high dose (50 mg; n = 10) or low dose (100 µg; n = 10) of intravenous immunoglobulin (IVIG) (Figure S5B in Supplementary Material). The positive control group received PBS instead of Abs (n = 10). (A) Pooled popliteal and brachial lymph nodes (LN) of each mouse from the indicated groups were analyzed on day 47 to determine total cell counts and the frequencies of activated CD4⁺CD44⁺CD62L⁻ T cells, CD4⁺IFNγ⁺ Th1 cells and CD4⁺IL-17⁺ Th17 cells. (B) Col II-reactive IgG2a_b and IgG2b serum Ab levels measured on day 42 by enzyme-linked immunofluorescence assay (ELISA). One representative experiment out of two independent experiments is shown. (C) Sialylation of Col II-specific IgG1 Abs inhibits IL-6 secretion by dendritic cells (DCs). Bone marrow-derived DCs from Fcgr2b^−/− mice were cultured in the presence of ICs containing 1 µg of Col II and 4 µg of different ratios of low-sialylated (< 1% sialylation; Figure 5B) and in vitro galactosylated and sialylated (46% sialylation; Figure 5B) Col II-specific IgG1 Abs (clone M2139; % of sialylation from left to right: <1, 3, 6, 12, 23, 46%). The IL-6 concentration in the supernatant was analyzed after 36 h via ELISA. The presented data are representative of four independent experiments.