TNFAIP3 and systemic sclerosis: In healthy donor skin biopsies (n = 6) A20 was detectable primarily in the papillary dermis, while SSc skin biopsies (n = 8; Cohort 1, Table 1) showed significantly reduced numbers of A20+ fibroblasts (p = 0.0007), most notable in the papillary dermis (Fig. 1B).