PDCD1 and pneumonitis: Patients (mainly those with melanoma and NSCLC) treated with PD-1/PD-L1 blockade were diagnosed with checkpoint inhibitor pneumonitis showing increased bronchoalveolar lavage (BAL) lymphocytosis, especially involving central memory T cells, and decreased expression of CTLA-4 and PD-1 in BAL Tregs (177).