In this topo I-induced SSc mouse model, programmed death (PD)-1 and one of its ligands, PD-L2, play an important role in the interaction between T cells and B cells, and inhibition of their binding suppressed IL-10 production from topo I antigen-specific B cells and enhanced autoimmune responses (Figure 8) (76). This evidence concerns the gene IL10 and systemic sclerosis.