Airway infection in stable lung transplant patients is associated with decreased intracellular T-helper type 1 pro-inflammatory cytokines in bronchoalveolar lavage T-cell subsets

: Current immunosuppression protocols to prevent lung transplant rejection reduce pro‐inflammatory and T‐helper type 1 (Th1) cytokines. However, Th1 T‐cell pro‐inflammatory cytokine production is important in host defense against bacterial infection in the lungs. Excessive immunosuppression of Th1 T‐cell pro‐inflammatory cytokines leaves patients susceptible to infection. To investigate whether pulmonary infection in lung transplant recipients is associated with reduced Th1 T‐cell pro‐inflammatory cytokines, whole blood and bronchoalveolar lavage (BAL) fluid from 13 stable lung transplant patients with ‘culture‐negative’ BAL and 13 patients with ‘culture‐positive’ BAL was stimulated in vitro, and cytokine production by CD8+ and CD4+ T‐cell subsets was determined using multiparameter flow cytometry. In BAL samples, there was a significant decrease in interleukin‐2 (IL2) in CD3+ T cells and tumor necrosis factor‐α (TNF‐α) in CD8+ T cells (but not CD4+) in ‘culture‐positive’ compared with ‘culture‐negative’ transplant patients. There was no difference in blood Th1 T‐cell cytokines between ‘culture‐positive’ compared with ‘culture‐negative’ transplant patients. A decrease in Th1 cytokines IL‐2 and TNF‐α in BAL T‐cell subsets is associated with isolation of potentially pathogenic organisms in the lungs in stable lung transplant patients. Excessive immunosuppression of these Th1 T‐cell pro‐inflammatory cytokines in stable transplant patients may leave them susceptible to infection. Modifying immunosuppression by monitoring intracellular Th1 pro‐inflammatory cytokines in BAL T cells may help to improve morbidity and infection rates in stable lung transplant patients.