Poststorage Leuko-Depleted Plasma Inhibits T-Cell Proliferation and Th1 Response In Vitro: Characterization of TGFβ-1 as an Important Immunomodulatory Component in Stored Blood

BACKGROUND

Poststorage, leuko-depleted blood transfusions have been associated with increased postoperative infections and improved allograft survival compared with prestorage leukocyte-depleted blood transfusion. Although the mechanism of this phenomenon remains to be fully elucidated, it is clear that the immunomodulatory effect is mediated by leukocytes/platelets or their products.

METHOD

The aim of this study was to investigate the in vitro effects of pre- and poststorage leuko-depleted plasma (LDP) and buffy coat LDP on T-cell proliferation and cytokine synthesis using multiparameter flow cytometry.

RESULTS

In cell cultures exposed to prestorage LDP and buffy coat LDP there were no significant changes compared with fresh blood. In cell cultures exposed to poststorage LDP, T-cells showed reduced expression of CD69, CD25 (IL-2Ralpha), CD122 (IL-2Rbeta) and CD132 (IL-2Rtau) and production of TNF-alpha and IL-2 but there was no significant alteration for IFN-tau or IL-4. Changes in cytokine/cytokine receptor synthesis and T-cell proliferation were shown to be directly proportional to poststorage LDP concentration. Some of these changes were characteristic of TGFbeta-1. Addition of TGFbeta-1 neutralising antibody to poststorage LDP, negated the immunosuppressive effect on PHA-stimulated PBMC cultures.

CONCLUSIONS

The decrease in T-cell proliferation and Th1 cytokines TNF-alpha and IL-2, may be one basis of altered immunoregulation resulting in increased rates of certain types of infections and increased graft tolerance reported in patients receiving poststorage LD blood transfusions. TGFbeta-1 is a major immunomodulatory component of poststorage LD blood transfusions.

Up-regulation of interleukin-8, interleukin-10, monocyte chemotactic protein-1, and monocyte chemotactic protein-3 in peripheral blood monocytes in stable lung transplant recipients: are immunosuppression regimens working?

BACKGROUND

Alveolar macrophages are a major source of inflammatory cytokines and chemokines involved in the pathogenesis of lung transplant rejection and are derived from blood monocytes that migrate to the lung. Levels of monocyte cytokines and chemokines that may be relevant in transplant rejection have not previously been determined in transplant recipients. We hypothesized that production of these inflammatory mediators by blood monocytes may be up-regulated despite the use of potent immunosuppression therapy.

METHOD

To investigate this, whole blood from 9 stable lung transplant recipients and 12 control volunteers was stimulated with lipopolysaccharide in vitro, and intracellular chemokine and cytokine production were determined with multiparameter flow cytometry.

RESULTS

Monocyte production of chemokines interleukin (IL)-8, monocyte chemotactic protein (MCP)-1, and MCP-3, and anti-inflammatory cytokine IL-10 were significantly increased in the lung transplant group, but IL-6, tumor necrosis factor-alpha, IL-1alpha, IL-12, macrophage inflammatory protein-1alpha, macrophage inflammatory protein-1beta, and transforming growth factor-beta levels were unchanged.

CONCLUSIONS

Because MCP-3 is a major chemoattractant for leukocytes to sites of antigenic challenge and is a natural ligand for MCP-1 receptor, this novel finding has important implications for the pathogenesis of lung transplant rejection. We now provide evidence that current immunosuppression protocols have a limited effect on monocyte inflammatory cytokine production and do not adequately suppress monocyte IL-8, MCP-1, and MCP-3 chemokine production. Drugs that modulate the action of these chemokines may improve current protocols for reducing graft rejection. Intracellular chemokine and cytokine analysis with flow cytometry may be a more accurate indicator of immunosuppression than drug levels in these patients.

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

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 TNFalpha production was significantly reduced from lung transplant patients compared to controls. CD4+ T-cell production of IFNgamma was also significantly reduced from lung transplant patients but production of IFNgamma 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 IFNgamma from transplant patients. T-cell IL-4 and CD8+ T-cell production of TGFbeta was significantly increased from lung transplant patients. We now provide evidence that current immunosuppression protocols have limited effect on peripheral blood IFNgamma production by CD8+ T-cells but do up-regulate T-cell anti-inflammatory cytokines. Drugs that effectively reduce IFNgamma 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.