S100A8 and idiopathic pulmonary arterial hypertension: So we speculated that the lower level of S100A9 and S100A8 may contribute to anti-apoptosis in IPAH, and S100A8/S100A9 may be a potential treatment in IPAH.Rnase2 encoded by RNASE2, is a cytotoxic protein secreted mainly by eosinophils as well as macrophages.