Figure 5. The effect of XmAb5871 on total and citrullinated peptide-specific IgG production as detected by ELISPOT assay (A) Purified human B cells were cultured with anti-Ig (2.5 μg/ml) or CpG (0.5 μg/ml) for 3 d in the presence of IL-2 (50 ng/ml) and IL-10 (50 ng/ml), and XmAb5871 or XENP6187 (10 μg/ml), respectively. The number of IgG-secreting cells was evaluated by ELISPOT assay on anti-IgG-coated nitrocellulose plates. Data represent the mean ± SD of seven independent experiments. *: P < 0.05. (B) B cells were stimulated by IL-2 (10 ng/ml) and R848 (1 μg/ml) for 3 d in the presence of XENP6187 or XmAb5871 antibodies. The number of IgG-secreting cells was assessed as above. Data represent the mean ± SD of seven independent experiments. *: P < 0.05. (C) Citrullinated filaggrin peptide-specific IgG-producing B cells were tested upon activation with IL-2 (10 ng/ml) and R848 (1 μg/ml) for 3 d with or without XmAb5871. The citrullinated filaggrin peptide-specific IgG secreting cells were detected on peptide-coated nitrocellulose plates. The results for B cells from six different ACPA-positive RA patients are shown. XmAb5871 significantly inhibited the development of citrullin-containing filaggrin peptide-specific antibody-forming cells, *: P < 0.05.