CCR2 regulates monocyte recruitment as well as CD4 T1 allorecognition after lung transplantation

CXCL10 and CXCL13 Expression were highly up-regulated in peripheral blood mononuclear cells in acute rejection and poor response to anti-rejection therapy

BACKGROUND

Acute rejection is still one of the main complications which enhances the cost and the risk to renal graft failure. Chemokines, interacting with respective receptors, can recruit leukocytes into grafts and mediate allograft rejection. In this study, we aimed to analyze gene expression of chemokines including CCL5/RANTES, CXCL10/IP-10, CXCL13/BCA-1, and receptors of CCR5, CXCR3, CXCR5 in peripheral blood mononuclear cells (PBMCs) during acute renal allograft rejection

METHODS

Gene expression of all these chemokines and receptors in PBMCs were analyzed by real-time PCR from 14 stable recipients, 32 biopsy-proven acute rejection (AR), and 5 acute tubular necrosis (ATN).

RESULTS

Gene expression of CCL5, CXCL10, CXCL13, and CCR5 were up-regulated both in AR and ATN group compared to stable recipients (fold change>2, P<0.05). Serum creatinine recovered to baseline level after anti-rejection therapy was defined as AR-sensitive and creatinine maintained above 200 μmol/L as AR-resistant. Expression of CXCL10 and CXCL13 were 5.98-, 2.94-, and 20.5, 10.8-fold change in AR-resistant and AR-sensitive compared to stable recipients, respectively. The expression of CXCL10 and CXCL13 was a twofold change in AR-resistant compared to AR-sensitive recipients (P<0.05). Five out of ten AR-resistant recipients lost graft function in the follow-up.

CONCLUSION

CXCL10 and CXCL13 expression were highly up-regulated in PBMCs in acute renal allograft rejection, especially in poor response to anti-rejection therapy and detrimental prognosis.

Innate immune activation by the viral PAMP poly I:C potentiates pulmonary graft-versus-host disease after allogeneic hematopoietic cell transplant

Respiratory viral infections cause significant morbidity and increase the risk for chronic pulmonary graft-versus-host disease (GVHD) after hematopoietic cell transplantation (HCT). Our overall hypothesis is that local innate immune activation potentiates adaptive alloimmunity. In this study, we hypothesized that a viral pathogen-associated molecular pattern (PAMP) alone can potentiate pulmonary GVHD after allogeneic HCT. We, therefore, examined the effect of pulmonary exposure to polyinosinic:polycytidylic acid (poly I:C), a viral mimetic that activates innate immunity, in an established murine HCT model. Poly I:C-induced a marked pulmonary T cell response in allogeneic HCT mice as compared to syngeneic HCT, with increased CD4+ cells in the lung fluid and tissue. This lymphocytic inflammation persisted at 2 weeks post poly I:C exposure in allogeneic mice and was associated with CD3+ cell infiltration into the bronchiolar epithelium and features of epithelial injury. In vitro, poly I:C enhanced allospecific proliferation in a mixed lymphocyte reaction. In vivo, poly I:C exposure was associated with an early increase in pulmonary monocyte recruitment and activation as well as a decrease in CD4+FOXP3+ regulatory T cells in allogeneic mice as compared to syngeneic. In contrast, intrapulmonary poly I:C did not alter the extent of systemic GVHD in either syngeneic or allogeneic mice. Collectively, our results suggest that local activation of pulmonary innate immunity by a viral molecular pattern represents a novel pathway that contributes to pulmonary GVHD after allogeneic HCT, through a mechanism that includes increased recruitment and maturation of intrapulmonary monocytes.

In vivo two-photon imaging reveals monocyte-dependent neutrophil extravasation during pulmonary inflammation

Immune-mediated pulmonary diseases are a significant public health concern. Analysis of leukocyte behavior in the lung is essential for understanding cellular mechanisms that contribute to normal and diseased states. Here, we used two-photon imaging to study neutrophil extravasation from pulmonary vessels and subsequent interstitial migration. We found that the lungs contained a significant pool of tissue-resident neutrophils in the steady state. In response to inflammation produced by bacterial challenge or transplant-mediated, ischemia-reperfusion injury, neutrophils were rapidly recruited from the circulation and patrolled the interstitium and airspaces of the lung. Motile neutrophils often aggregated in dynamic clusters that formed and dispersed over tens of minutes. These clusters were associated with CD115(+) F4/80(+) Ly6C(+) cells that had recently entered the lung. The depletion of blood monocytes with clodronate liposomes reduced neutrophil clustering in the lung, but acted by inhibiting neutrophil transendothelial migration upstream of interstitial migration. Our results suggest that a subset of monocytes serve as key regulators of neutrophil extravasation in the lung and may be an attractive target for the treatment of inflammatory pulmonary diseases.

Two-photon microscopy in pulmonary research

As the lung is constantly exposed to both innocuous and potentially noxious antigens, a thorough understanding of both innate and adaptive immune responses in this organ is of the essence. Imaging modalities such as magnetic resonance imaging, positron emission tomography, and confocal microscopy have expanded our knowledge about various molecular processes and cellular responses in the lung. Two-photon microscopy has evolved into a powerful tool to observe cellular interactions in real time and has markedly expanded our understanding of the immune system. Recently, two-photon microscopy has also been utilized to image the murine lung. As immune responses in the lung differ from those in other non-lymphoid tissues, this technique holds great promise to advance our knowledge of the biology that underlies a wide spectrum of pulmonary diseases.