A study investigating sirolimus-associated pneumonitis reported the presence of lymphocytic alveolitis in bronchoalveolar lavage of all 8 patients analyzed, mostly of the CD4 type, suggesting a cell-mediated autoimmune response.19 While there are conflicting studies about the direct toxic effect and dose-related effect19, 20, there are an increasing number of preclinical studies suggesting that pulmonary inflammation could be due to cytokine production by mTOR inhibitors.21 This evidence concerns the gene MTOR and pneumonitis.