Intracellular cytokines in blood T cells in lung transplant patients – a more relevant indicator of immunosuppression than drug levels

Abstract

Summary Allograft rejection remains a major cause of morbidity and mortality following lung transplantation and is associated with an increase in T-cell pro-inflammatory cytokine expression. Systemic levels of immunosuppressive drugs used to reduce pro-inflammatory cytokine expression are closely monitored to their ‘therapeutic range’. However, it is currently unknown if levels of these drugs correlate with pro-inflammatory cytokine expression in peripheral blood T cells. To investigate the immunomodulatory effects of currently used immunosuppressive regimes on peripheral blood T-cell cytokine production, whole blood from stable lung transplant patients and control volunteers  were  stimulated in vitro and cytokine production by CD8+ and CD4+ T-cell subsets determined using multiparameter flow cytometry. T-cell IL-2 and TNFα production was significantly reduced from lung transplant patients compared to controls. CD4+ T-cell production of IFNγ was also significantly reduced from lung transplant patients but production of IFNγ by CD8+ T cells remained unchanged. There was an excellent correlation between the percentage of CD8+ T cells and the percentage of CD8+ T cells producing IFNγ from transplant patients. T-cell IL-4 and CD8+ T-cell production of TGFβ was significantly increased from lung transplant patients. We now provide evidence that current immunosuppression protocols have limited effect on peripheral blood IFNγ production by CD8+ T-cells but do up-regulate T-cell anti-inflammatory cytokines. Drugs that effectively reduce IFNγ production by CD8+ T cells may improve current protocols for reducing graft rejection in these patients. Intracellular cytokine analysis using flow cytometry may be a more appropriate indicator of immunosuppression than drug levels in these patients. This technique may prove useful in optimizing therapy for individual patients.