CD40LG and systemic sclerosis: IgM memory [8.57% (IQR 4.62–19.15) vs. 21.3% (IQR 15.8–29.8), p < 0.001] and switched memory [14.15% (IQR 8.5–20.2) vs. 19.5% (IQR 16.1–21.9), p < 0.05] were significantly lower in SSc patients than HCs.