TNFSF13B and pulmonary arterial hypertension: Recently, soluble markers of B cell activation were found to be elevated in the serum of SSc patients; in particular, a correlation was shown between serum levels of B-cell activating factor (BAFF), NT-proBNP levels and forced vital capacity (FVC)/DLCO ratio in lcSSc-PAH patients, although, overall, serum BAFF levels were not significantly higher in SSc patients with PAH vs. those without PAH [149].