BackgroundLung transplantation cases have immunosuppression maintainedusing a calcineurin inhibitor, anti-metabolites, and steroid. Case ReportWe report 2 clinical cases inwhich anti-metabolites (mycophenolate mofetil) were successfully withdrawn after livingdonor lobar lung transplantation by monitoring immune function using the ImmuKnow®assay. In the first case, a 43-year-old woman underwent living donor lobar lungtransplantation for pulmonary alveolar proteinosis. Two healthy relatives donated alower lobe each. Immunosuppression was maintained using tacrolimus, mycophenolatemofetil, and steroid. Six months posttransplantation, she developed invasivepulmonary aspergillosis. During anti-fungal treatment, we withdrew mycophenolate mofetiland tacrolimus trough levels were kept around 8 ng/mL. Despite the resultinglow-level immunosuppression, the ImmuKnow assay showed immune function to bein the moderate range with tacrolimus and steroid alone, encouraging us tomaintain this strategy to avoid recurrence of invasive pulmonary aspergillosis. In thesecond case, a 24-year-old man underwent living donor lobar lung transplantation forcystic fibrosis. Two healthy relatives donated a lower lobe each. Immunosuppressionwas maintained using tacrolimus, mycophenolate mofetil, and steroid. Five monthsposttransplantation, he developed persistent Pseudomonas aeruginosa pneumonia derivedfrom the paranasal sinuses. Under ImmuKnow assay monitoring, mycophenolate mofetilwas withdrawn, but immune function was maintained within the moderate range usingtacrolimus and steroid alone. DiscussionRespiratory function in both cases was maintained; nofindings of bronchiolitis obliterans syndrome were noted during this period. To the bestof our knowledge, no reports have described successful anti-metabolite withdrawal inlung transplantation with ImmuKnow monitoring. Immune evaluation by ImmuKnowcould offer a useful method to monitor and control immune status, particularly amongrecipients susceptible to infection, revealing that moderate immune function could bemaintained using tacrolimus and steroid in living donor lobar lung transplantation.