Monoclonal anti-AChR antibodies increase IL-6 production by muscle cells. The LHCNM2 cells were cultured as described in the Materials and Methods section, as myoblasts or after differentiation into myotubes. (A) IL-6 production was measured by ELISA and normalized to controls (without antibody). Myotubes were treated with anti-AChR antibodies (198, 155, 35 and Acrys), their isotype controls (IgG2a, IgG1), or left untreated (Ctl). The data come from four experiments, each including 4–6 replicates. (B) For some antibodies, the effect on myotubes (black bars) and myoblasts (white bars) was compared. The data come from three experiments, each including 2–4 replicates. (C) The expression of AChR subunits in myotubes (black bars) and myoblasts (white bars) was assessed by Q-RT-PCR (n = 4). (D) Addition of the anti-AChR mAb 198 was performed at several time points and all supernatants were analyzed at 72 h. mAb 198 was added once (bar A), twice (bars B and C), or at three consecutive time points (bar D). The results shown are from two wells for each condition in a representative experiment. Bars and error bars represent mean ± SEM. ***p < 0.001; **p < 0.01; *p < 0.05.