TGFB1 and systemic sclerosis: In contrast, cluster 5 exhibits substantial increases in a wide range of Proteobacteria and other Gram-negative taxa in SSc patients (p < 0.001 by paired t-test) and is strongly correlated with KEGG immune activation pathways, including Toll-like receptor (TLR) and TGFβ signaling (Fig. 4a, d).