IL1A and systemic sclerosis: Treatment with SSc IgG (10 μg/mL) was associated with significantly higher levels of IL-1α secreted into the media, when compared to control IgG treatment or media alone (p < 0.0001 for SSc IgG treated versus untreated, p < 0.002 for SSc IgG versus HC IgG) (Figure 3A).