Thus, it is difficult to relate the IL6+ transgenic mouse to any particular group of the human disease, but it appears to have features of Group 1 PAH and Group 3 PH, the latter based on histology images showing lung parenchymal differences (increased fibrotic changes and abnormal enlargement of lung air spaces; Figure 3C) from WT mice. This evidence concerns the gene IL6 and pulmonary arterial hypertension.