CXCL9 and pulmonary arterial hypertension: Previously, it has been shown that CXCL9 and several CC-family chemokines important for chemotaxis of myeloid cells play a central role in distinguishing clusters of PAH immune phenotypes with different clinical risks [26] The finding that CXCL13 is one of the markers that could be linked to survival in our PCA/MFA analysis (Fig. 5d) may support a critical role of B cell recruitment and organization in follicles and germinal centers in PAH.