The plasminogen activation system plays an integral role in the migration of macrophages in response to an inflammatory stimulus, and the binding of plasminogen to its cell-surface receptor initiates this process. Although previous studies from our laboratory have shown the importance of the plasminogen receptor S100A10 in cancer cell plasmin production, the potential role of this protein in macrophage migration has not been investigated. Using thioglycollate to induce a peritoneal inflammatory response, we demonstrate, for the first time, that compared with wild-type (WT) mice, macrophage migration across the peritoneal membrane into the peritoneal cavity in S100A10-deficient (S100A10 ؊/؊ ) mice was decreased by up to 53% at 24, 48, and 72 hours. Furthermore, the number of S100A10-deficient macrophages that infiltrated Matrigel plugs was reduced by 8-fold compared with their WT counterpart in vivo. Compared with WT macrophages, macrophages from S100A10 ؊/؊ mice demonstrated a 50% reduction in plasmin-dependent invasion across a Matrigel barrier and a 45% reduction in plasmin generation in vitro. This loss in plasmin-dependent invasion was in part the result of a decreased generation of plasmin and a decreased activation of pro-MMP-9 by S100A10-deficient macrophages. This study establishes a direct involvement of S100A10 in macrophage recruitment in response to inflammatory stimuli. (Blood. 2010;116(7): 1136-1146) IntroductionMonocytes/macrophages play a central role in pathogenic inflammatory responses associated with atherosclerosis, restenosis, tumor surveillance, and arthritis. [1][2][3] In response to changes in the cellular environment, monocytes and monocytoid cells undergo extensive phenotypic alterations, including marked changes in their fibrinolytic properties. Synthesis and activation of matrix-degrading proteinases by monocytes and macrophages play an essential role in their migration through tissue. A key proteinase that participates in pericellular proteolysis is the serine proteinase plasmin. Plasmin is a broad substrate proteinase that is formed from the inactive zymogen plasminogen (Plg) by the Plg activators, tissue Plg activator (tPA) and urokinase-type Plg activator (uPA). 4,5 The participation of plasmin in cell invasion and migration is dependent on the ability of plasmin not only to degrade extracellular matrix (ECM) proteins but to also activate other proteinases that have matrix-degrading activity. Plasmin can degrade a variety of matrix proteins, such as laminin and fibronectin, and appears to activate matrix metalloproteinase-1 (MMP-1), MMP-3, and MMP-13 directly, and to activate MMP-2 and MMP-9 indirectly, thereby facilitating cell migration through ECMs. 6 The assembly of Plg and its activators on the cell surface is facilitated by the protein S100A10 (also referred to as p11). S100A10 is a member of the S100 family of calcium-binding proteins and is typically found in most cells bound to its annexin A2 (p36) ligand as the heterotetrameric (S100A10) 2 -(annexin A2) 2 complex, annexi...

Cell transplantation into adult zebrafish has lagged behind mouse due to the lack of immune compromised models. Here, we have created homozygous rag2E450fs mutant zebrafish that have reduced numbers of functional T and B cells but are viable and fecund. Mutant fish engraft zebrafish muscle, blood stem cells, and cancers. rag2E450fs mutant zebrafish are the first immune compromised zebrafish model that permits robust, long-term engraftment of multiple tissues and cancer.

Dendritic cells (DC) actively rearrange their actin cytoskeleton to participate in formation of the immunological synapse (IS). In this study, we evaluated the requirements for DC participation in the IS. DC rearrange their actin cytoskeleton toward naive CD4+ T cells only in the presence of specific MHC-peptide complexes. In contrast, naive CD4+ T cells polarized their cytoskeletal proteins in the absence of Ag. DC cytoskeletal rearrangement occurred at the same threshold of peptide-MHC complexes as that required for T cell activation. Furthermore, T cell activation was inhibited by specific blockade of DC cytoskeletal rearrangement. When TCR-MHC interaction was bypassed by using Con A-activated T cells, DC polarization was abrogated. In addition, directional ligation of MHC class II resulted in DC cytoskeletal polarization. Our findings suggest that a high Ag specificity is required for DC IS formation and that MHC class II signaling plays a central role in this process.

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