Rat Anti-Mouse CD18 Monoclonal antibody, clone M18/2 Functional Grade

Chronic inflammation is highly correlated with the development of colorectal cancer. Proteinase-activated receptor 2 (PAR2) plays pro-inflammatory roles in many type of cancers. By using trypsin or PAR2-activating peptide (AP2), we found PAR2 activation promotes the proliferation and migration of human colorectal cancer cells HT-29 and SW620. To clarify the downstream signaling of PAR2, we examined interleukin-8 (IL-8) secretion in human colorectal cancer cells. Trypsin and AP2 could up-regulate the expression and secretion of IL-8. Further, autocrine IL-8 activated ERK and AKT signaling pathways in cancer cells through CXCR1/2. The phosphorylation of ERK and AKT were suppressed by reparixin, an inhibitor of CXCR1/2. Together, PAR2 triggers autocrine IL-8 signaling pathway to promote proliferation and migration of colorectal cancer cells.

The number of leukocytes present in circulation varies throughout the day, reflecting bone marrow output and emigration from blood into tissues. Using an organism-wide circadian screening approach, we detected oscillations in pro-migratory factors that were distinct for specific vascular beds and individual leukocyte subsets. This rhythmic molecular signature governed time-of-day-dependent homing behavior of leukocyte subsets to specific organs. Ablation of BMAL1, a transcription factor central to circadian clock function, in endothelial cells or leukocyte subsets demonstrated that rhythmic recruitment is dependent on both microenvironmental and cell-autonomous oscillations. These oscillatory patterns defined leukocyte trafficking in both homeostasis and inflammation and determined detectable tumor burden in blood cancer models. Rhythms in the expression of pro-migratory factors and migration capacities were preserved in human primary leukocytes. The definition of spatial and temporal expression profiles of pro-migratory factors guiding leukocyte migration patterns to organs provides a resource for the further study of the impact of circadian rhythms in immunity.

A hallmark of T cell activation in vitro and in vivo is the clustering of T cells with each other via interaction of the LFA-1 integrin with ICAM-1. The functional significance of these homotypic aggregates in regulating T cell function remains unknown. We used an APC-free in vitro activation system to demonstrate that stimulation of purified naive CD8 T cells results in enhanced expression of ICAM-1 on T cells that is sustained by the inflammatory cytokine IL-12 and associated with robust T cell aggregates. ICAM-1-deficient CD8 T cells proliferate normally but demonstrate a striking failure to aggregate. Interestingly, loss of ICAM-1 expression results in elevated levels of IFN-gamma and granzyme B, as well as enhanced cytotoxicity. Similar results were obtained when anti-LFA-1 Ab was used to block the clustering of wild-type T cells. ICAM-1 ligation is not required for IFN-gamma regulation, as clustering of ICAM-1-deficient CD8 T cells with wild-type T cells reduces IFN-gamma expression. Analysis using a fluorescent reporter that monitors TCR signal strength indicates that T cell clustering limits T cell exposure to Ag during activation. Furthermore, T cell clustering promotes the upregulation of the CTLA-4 inhibitory receptor and the downregulation of eomesodermin, which controls effector molecule expression. Activation of ICAM-1-deficient CD8 T cells in vivo results in an enhanced percentage of KLRG-1(+) T cells indicative of short-lived effectors. These results suggest that T cell clustering represents a mechanism that allows continued proliferation but regulates T cell effector function and differentiation.