KITLG and pulmonary hypertension, primary, 1: Kitamura et al. were the first to study changes between the bone marrow (BM) niche before and after CAR‐T‐cell infusion and its relationship with PHT, reporting that PHT patients tended to have a lower area proportion of CD271+ cells, which are proposed as numbers of HSPC niches, lower levels of CXCL12 and SCF in BM before CAR‐T‐cell infusion, and increased inflammation‐related cytokine levels of IL‐6 and monocyte chemoattractant protein‐1 in BM.15