The gastrointestinal tract (GIT) is a primary site for human immunodeficiency virus (HIV) and simian immunodeficiency virus (SIV) infection, replication, and dissemination. After an initial explosive phase of infection, HIV establishes latency. In addition to CD4 T cells, macrophages are readily infected, which can persist for long periods of time. Though macrophages at various systemic sites are infected, those present in the GIT constitute a major cellular reservoir due to the abundance of these cells at mucosal sites. Here, we review some of the important findings regarding what is known about the macrophage reservoir in the gut and explore potential approaches being pursued in the field to reduce this reservoir. The development of strategies that can lead to a functional cure will need to incorporate approaches that can eradicate the macrophage reservoir in the GIT. Macrophages are one of the most abundant immune cells in the gut (1, 2). Morphologically, gut macrophages are similar to most resident tissue macrophages, with a mononuclear shape and a granular cytoplasm, and they are highly phagocytic and microbicidal (3-5). They express major histocompatibility complex (MHC) class II, CD36, CD68, CD163 (6, 7), and CD209 (7) but have low levels of CD80, CD86, and CD40 (8-11). Unlike monocytes in peripheral blood that are largely CD14 ϩ , human mucosal macrophages in the gut have been shown to express aϪ phenotype (12, 13). The expression of CD4 and CCR5/CXCR4 key receptors for human immunodeficiency virus (HIV) infection, on macrophage populations has been shown to differ based on the sites the cells reside in. Shen et al. (14) showed that vaginal macrophages expressed CD4 and CCR5/CXCR4 similarly to blood monocytes, whereas intestinal macrophages expressed little or no detectable CD4 and CCR5/CXCR4 (15-17).Interestingly, under normal conditions or in response to Tolllike receptor (TLR) ligands, gut macrophages constitutively secrete anti-inflammatory cytokines, such as interleukin-10 (IL-10), rather than proinflammatory mediators, such as IL-12, IL-23, tumor necrosis factor alpha (TNF-␣), IL-1, IL-6, and interferoninducible protein 10 (IP-10) (18)(19)(20)(21)(22), suggesting that intestinal macrophages may be critical for maintaining immune homeostasis in the gastrointestinal tract (6). Smythies et al. (23) reported that intestinal macrophages displayed significant inflammation anergy even though they had avid phagocytic and bactericidal activity. Depletion of mucosal macrophages was shown to be associated with increased susceptibility to colitis and graft-versus-host disease in mice (24-26). Likewise, altering the phenotype of macrophages to that of a proinflammatory phenotype as seen during HIV replication was associated with increased inflammation and tissue damage (27).In addition to their role in maintaining mucosal immune homeostasis, gut macrophages, like dendritic cells (DC), have been shown to sample microbes directly from the intestinal lumen and transfer these antigens to DC for processing or tran...

We have developed a novel ELISA using an optimized ARGS antibody and have demonstrated for the first time, an ELISA-based measurement of aggrecan degradation products in human serum and urine. This assay has the potential to serve as a mechanistic drug activity biomarker in the clinic and is expected to significantly impact/accelerate the clinical development of aggrecanase inhibitors and other disease modifying drugs for OA.

UNITED KINGDOM, 15 , Univ. Regensburg, Regensburg/GERMANY Although the adoptive transfer of allograft tolerance with suppressor cell populations is a common method in experimental Immunology, there remain substantial obstacles to clinical implementation of the technique. Self-evidently, any suppressor cell preparation intended for use as a tolerance-promoting therapy must be predictably efficacious and safe for the recipient which, in practical terms, means that the cells must be consistent in phenotype and function, and that their properties remain unaltered by administration. The human regulatory macrophage is a novel type of suppressor macrophage which may be a particularly suitable cell for promoting transplantation tolerance in the clinical setting because of its stable phenotype and T cellsuppressive activity. Human regulatory macrophages (M reg) arise when isolated CD14 + monocytes are cultivated in the presence of high concentrations of human serum for six days prior to maturation with IFN-γ. M regs are readily distinguished from macrophages in other activation states by their characteristic morphology and homogeneous CD14 -/low CD16 -/low CD80 -/low CD86 + HLA-DR int CD163 -TLR2 -TLR4 -cell surface phenotype. By raising monoclonal antibodies, DHRS9 was discovered to be a specific marker of M regs. Microarray analyses comparing M regs to a panel of differentially polarised macrophages confirmed the uniqueness and stability of the M reg phenotype, and identified CD258 (LIGHT) and CD85H (LILRA2) as additional M reg markers. Naturally-occurring DHRS9-expressing macrophages were detected in human spleen and we tentatively suggest that these represent physiological conterparts of the in vitro-derived M reg. It is thought that the M reg represents a committed state of macrophage differentiation and that its generation in vitro somehow recapitulates the in vivo development of tissue macrophages from CD16 + resident monocytes. Acquisition of the M reg phenotype by monocytes is a gradual process which depends upon plastic adherence and exposure to serum immunoglobulin. The M reg-inducing activity of immunoglobulin is attributed to signalling through Fc γ RIII and not Fc γ RIIb. M regs profoundly suppress mitogen-stimulated and alloantigen-driven T cell proliferation by deleting activated T cells. This suppressive activity of M regs has both a contact-dependent and contact-independent component; the latter can be partly attributed to the action of indoleamine 2,3-dioxygenase. Building on evidence from preclinical transplant studies that preoperative treatment with donor-derived M regs promotes allograft survival (abstract #2485) M regs were administered to two living-donor renal transplant recipients. Both patients were minimised to low-dose tacrolimus monotherapy within 24 weeks of transplantation and subsequently maintained excellent graft function. By one year, both patients displayed patterns of peripheral blood gene expression converging upon the IOT-RISET tolerance signature (J. Clin. Invest. 2010; 120(6):184...

Using hybridoma technology we established a panel of human monoclonal rheumatoid factors (RF) from the synovial tissues of two patients with rheumatoid arthritis (RA), and one patient with polyarticular juvenile RA. Nucleotide sequence analysis of the V regions of these RF indicates that two independently derived antibodies from one of the RA patients are clonally related. One of these antibodies appears to be close to germ-line configuration, whereas the other has accumulated a total of 36 substitutions in both H and L chains. Measurements of the affinity for human IgG of the two RF show that the extensively mutated RF has 100-fold higher affinity for IgG than the RF close to germline. These findings indicate that IgM RF in RA can undergo affinity maturation and suggest that certain RF may be the product of an Ag-driven immune response.