CD4 and pneumonitis: 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