PI15 and pulmonary fibrosis: While a number of these transcripts, including ADAMTS family members (ADAMTS4, ADAMTS9) [10], AGER [11], HIF-1α [12, 13], serpin family members (SERPINA3, SERPINE2) [14], and selectin E (SELE) [15] have an established role in lung fibrosis, expression of novel IIP candidate genes such as rhotekin 2 (RTKN2) and peptidase inhibitor 15 (PI15) is also significantly altered in severe compared to mild disease.