Compartmentalization of intracellular proinflammatory cytokines in bronchial intraepithelial T cells of stable lung transplant patients

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Abstract
Allograft rejection remains a major cause of morbidity and mortality following lung transplantation and is associated with an increased expression of T cell proinflammatory cytokines. We have shown that CD4+ T cell proinflammatory cytokine production was significantly reduced in peripheral blood and bronchoalveolar lavage (BAL) of stable lung transplant patients, consistent with immunosuppression therapy. However, analysis of inflammatory cytokine profiles of intraepithelial T cells in bronchial brushing (BB) may be more relevant than peripheral blood or BAL T cells for assessing immune graft status. To investigate the immunomodulatory effects of currently used immunosuppressive regimens on bronchial intraepithelial T cell cytokine production, whole blood, BAL and BB from stable lung transplant patients and control volunteers were stimulated in vitro and cytokine production by CD8+ and CD4+ T cell subsets determined using multi-parameter flow cytometry. In bronchial intraepithelial T cell subsets in control subjects and transplant patients there was compartmentalization of interferon (IFN)-γ and tumour necrosis factor (TNF)-α production, a decrease in interleukin (IL)-2 production by CD4+ T cells and CD4 : CD8 inversion compared with blood and BAL. Although there was a decrease in T cell proinflammatory cytokine production in blood of transplant patients, this was not found in BAL or bronchial intraepithelial CD8 T cell subsets, suggesting that the same level of immunosuppression may not occur in the lung of transplant recipients. Drugs that effectively reduce CD8 T cell proinflammatory cytokine production in the lung compartment may improve current protocols for reducing graft rejection in these patients.