S100B and pulmonary arterial hypertension: The HIV proteins Nef and Tat contribute to key processes in PAH including vasoconstriction, cellular proliferation, inflammation, and thrombosis.[7,8] Our group has recently shown that asymmetric dimethylarginine (ADMA), a marker of nitric oxide mediated endothelial dysfunction that accumulates with chronic inflammation, independently predicts HIV-associated PAH.[9,10]