CD4-expressing cells are early mediators of the innate immune system during sepsis.

It is well established that the immune response to sepsis is mediated by leukocytes associated with the innate immune system. However, there is an emerging view that T lymphocytes can also mediate this response. Here, we observed a significant depletion of both CD4 and CD8 T cells in human patients after blunt trauma. To determine what effect the loss of these cells may have during a subsequent infection, we obtained CD4- and CD8-deficient mice and subjected them to cecal ligation and puncture (CLP). We observed that CD4 knockout (KO) mice showed increased CLP-induced mortality compared with CD8-deficient and wild-type (WT) mice especially within the first 30 h of injury. CD4 KO mice also exhibited significantly increased IL-6 concentrations after the CLP. The CD4 KO mice had an increased concentration of bacteremia as compared with WT mice. Antibiotic treatment decreased mortality in the CD4 KO mice as compared with no changes in the wild mice after CLP. Neutrophils isolated from septic CD4 KO mice showed decreased spontaneous oxidative burst compared with neutrophils taken from septic controls. We examined the role of IFN-gamma by using mice deficient in this cytokine and found these mice to have significantly higher mortality as compared with WT mice. Finally, we detected a 2-fold increase in CD11b+ cells that exhibited intracellular IFN-gamma staining in the peritoneum of WT mice after CLP. The data suggest that CD4+ cells may facilitate the early clearance of bacteria by regulating neutrophils function possibly through an IFN-gamma-dependent mechanism.

Differential immunological phenotypes are exhibited after scald and flame burns.

A dysfunctional immune system is known to be part of the pathophysiology after burn trauma. However, reports that support this have used a variety of methods, with numerous variables, to induce thermal injury. We hypothesized that, all other parameters being equal, an injury infliction by a scald would yield different immunological responses than one inflicted by a flame. Here, we demonstrated that both burn methods produced a full-thickness burn, yet there was more of an increase in subdermal temperature, hematocrit, mortality, and serum IL-6 concentrations associated with the scald burn. On postinjury day 1, the scald-burned mice showed diminished lymphocyte numbers, interferon gamma production, and lymphocyte T-bet expression as compared with sham- and flame-burned mice. On postburn day 8, spleens from both sets of thermally injured animals showed an increase in proinflammatory myeloid cells as compared with sham-burned mice. Furthermore, the T-cell numbers, T-bet expression, and phenotype were changed such that interferon gamma production was higher in scald-burned mice than in sham- and flame-burned mice. Altogether, the data show that differential immunological phenotypes were observed depending on the thermal injury method used.

Paclitaxel impairs endothelial cell adhesion but not cytokine-induced cellular adhesion molecule expression.

Local delivery of antiproliferative agents using drug-eluting stents has become a productive area of research for preventing in-stent restenosis. Recently, the microtubule stabilizing drug paclitaxel has been used to coat stents. While the actions of paclitaxel on smooth muscle are well documented, effects on endothelial cells (ECs) are largely unknown. Nevertheless, restoration of EC function is a critical step in repairing the vascular lesion. We assessed the effects of paclitaxel by examining three events that are critical in controlling the severity of vascular injury: (1) adhesion of ECs to matrix proteins, (2) EC migration, and (3) cytokine-stimulated cellular adhesion molecule (CAM) expression on the surface of ECs. Paclitaxel inhibited both EC adhesion and migration of ECs; however, it had no effect on tumor necrosis-stimulated CAM expression on ECs. The mechanisms of paclitaxel action on matrix adhesion and migration are not clear, but protein kinase C and myosin light chain kinase do not appear to play a role as they are unaffected by treatment of the cells with paclitaxel. On the other hand, the MAP kinase ERK1/2 is modestly inhibited by paclitaxel. While paclitaxel-coated endovascular stents may prevent smooth muscle proliferation, their attenuation of EC migration and adhesion to the lesion coupled with an inability to reduce cytokine-induced CAM expression on ECs may limit their effectiveness.

The role of the cytoskeleton in cellular adhesion molecule expression in tumor necrosis factor-stimulated endothelial cells.

Leukocyte infiltration is a hallmark of the atherosclerotic lesion. These cells are captured by cellular adhesion molecules (CAMs), including vascular cell adhesion molecule-1 (VCAM-1), intercellular adhesion molecule-1 (ICAM-1), platelet-endothelial cell adhesion molecule (PECAM), and E-selectin, on endothelial cells (EC). We examined the role of the actin cytoskeleton in tumor necrosis factor-alpha (TNF-alpha)-induced translocation of CAMs to the cell surface. Human aortic EC were grown on 96-well plates and an ELISA was used to assess surface expression of the CAMs. TNF-alpha increased VCAM-1, ICAM-1, and E-selectin by 4 h but had no affect on the expression of PECAM. A functioning actin cytoskeleton was important for VCAM-1 and ICAM-1 expression as both cytochalasin D, an actin filament disruptor, and jasplakinolide, an actin filament stabilizer, attenuated the expression of these CAMs. These compounds were ineffective in altering E-selectin surface expression. Myosin light chains are phosphorylated in response to TNF-alpha and this appears to be regulated by Rho kinase instead of myosin light chain kinase. However, the Rho kinase inhibitor, Y27632, had no affect on TNF-alpha-induced CAM expression. ML-7, a myosin light chain kinase inhibitor, had a modest inhibitory effect on the translocation of VCAM-1 but not on ICAM-1 or E-selectin. These data suggest that the surface expression of VCAM-1 and ICAM-1 is dependent on cycling of the actin cytoskeleton. Nevertheless, modulation of actin filaments via myosin light chain phosphorylation is not necessary. The regulation of E-selectin surface expression differs from that of the other CAMs.