Melanoma Cell Expression of CD200 Inhibits Tumor Formation and Lung Metastasis via Inhibition of Myeloid Cell Functions

CD200 is a cell surface glycoprotein that functions through engaging CD200 receptor on cells of the myeloid lineage and inhibits their functions. Expression of CD200 has been implicated in a variety of human cancer cells including melanoma cells and has been thought to play a protumor role. To investigate the role of cancer cell expression of CD200 in tumor formation and metastasis, we generated CD200-positive and CD200-negative B16 melanoma cells. Subcutaneous injection of CD200-positive B16 melanoma cells inhibited tumor formation and growth in C57BL/6 mice but not in Rag1−/−C57BL/6 mice. However, i.v. injection of CD200-positive B16 melanoma cells dramatically inhibited tumor foci formation in the lungs of both C57BL/6 and Rag1−/−C57BL6 mice. Flow cytometry analysis revealed higher expression of CD200R in Gr1+ myeloid cells in the lung than in peripheral myeloid cells. Depletion of Gr1+ cells or stimulation of CD200R with an agonistic antibody in vivo dramatically inhibited tumor foci formation in the lungs. In addition, treatment with tumor antigen specific CD4 or CD8 T cells or their combination yielded a survival advantage for CD200 positive tumor bearing mice over mice bearing CD200-negative tumors. Taken together, we have revealed a novel role for CD200-CD200R interaction in inhibiting tumor formation and metastasis. Targeting CD200R may represent a novel approach for cancer immunotherapy

DNA mismatch repair enzyme expression in synovial tissue

Objective: To examine the expression and distribution of MMR enzymes in synovial tissues from patients with arthritis and from normal subjects. Methods: Synovial tissues from patients with RA, osteoarthritis (OA), or normal subjects were analysed by immunohistochemistry using monoclonal antibodies to hMSH2, hMSH3, and hMSH6. MMR protein expression was evaluated by computer assisted digital image analysis. Results: hMSH2, hMSH3, and hMSH6 were found in most synovial tissues evaluated, with greater levels in the intimal lining than sublining regions. In RA and OA, sublining perivascular staining for hMSH6 and hMSH3 was also prominent. Significantly higher sublining expression of hMSH2, hMSH3, and hMSH6 was seen in RA and OA than in normal synovium. Double label immunohistochemistry demonstrated that the main cells expressing MMR enzymes were CD68(+) and CD68(–) cells in the intimal lining. Conclusions: DNA MMR enzyme expression is greatest in the synovial intimal lining layer, where maximal oxidative stress in RA occurs. Although MMR enzyme expression is greater in RA than in normal tissue, this compensatory response cannot overcome the genotoxic environment, and DNA damage accumulates

Role of peptidoglycan subtypes in the pathogenesis of bacterial cell wall arthritis

Background: Bacterial cell wall (CW) arthritis develops in susceptible strains of rats after a single intraperitoneal injection of the CW from certain bacterial species, both pathogenic and non-pathogenic. For the development of chronic bacterial CW arthritis, the structure of the bacterial peptidoglycan (PG) has been found to be decisive. Objective: To define the role of PG subtypes in the pathogenesis of chronic bacterial CW arthritis. Method: Arthritis was induced with CWs of Lactobacillus plantarum, L casei B, L casei C, and L fermentum. Gas chromatography-mass spectrometry was used to measure the presence of CW derived muramic acid in the liver and to determine PG subtypes. CWs were also tested for their resistance to lysozyme in vitro. Results: These results and those published previously indicate that PGs of CWs which induce chronic arthritis, no matter whether they were derived from strains of Streptococcus, Bifidobacterium, Collinsella, or Lactobacillus, all have lysine as the third amino acid of the PG stem peptide, representing PG subtypes A3α and A4α. Those strains which induce only transient acute arthritis or no arthritis at all do not have lysine in this position, resulting in different PG subtypes. Conclusions: In vivo degradation of only those PGs with the subtypes A3α and A4α leads to the occurrence of large CW fragments, which persist in tissue and have good proinflammatory ability. CWs with other PG subtypes, even if they are lysozyme resistant, do not cause chronic arthritis, because the released fragments are not phlogistic. It is emphasised that a variety of microbial components not causing inflammation have been found in animal and human synovial tissue

Analysing the effect of novel therapies on cytokine expression in experimental arthritis.

Type II collagen-induced arthritis (CIA) is an animal model of rheumatoid arthritis that has been used extensively to address questions of disease pathogenesis and to validate novel therapeutic targets. Susceptibility to CIA is strongly associated with major histocompatibility complex class II genes, and the development of arthritis is accompanied by a robust T- and B-cell response to type II collagen. The main pathological features of CIA include proliferative synovitis with infiltration of inflammatory cells, pannus formation, cartilage degradation, erosion of bone and fibrosis. Pro-inflammatory cytokines, such as tumour necrosis factor alpha and interleukin-1beta, are expressed in the arthritic joints in both murine CIA and human rheumatoid arthritis, and blockade of these molecules results in amelioration of disease. Hence, there is a great deal of interest in the development of small-molecular-weight inhibitors of pro-inflammatory cytokines. There is also interest in the development and testing of drugs with the capacity to modulate the immune pathways involved in driving the inflammatory response in arthritis. For these reasons, there is a need to monitor the effect of novel treatments on cytokine expression in vivo. In this review, we outline the various techniques used to detect cytokines in experimental arthritis and describe how these techniques have been used to quantify changes in cytokine expression following therapeutic intervention

Ligand-induced dimerization of Drosophila peptidoglycan recognition proteins in vitro

Drosophila knockout mutants have placed peptidoglycan recognition proteins (PGRPs) in the two major pathways controlling immune gene expression. We now examine PGRP affinities for peptidoglycan. PGRP-SA and PGRP-LCx are bona fide pattern recognition receptors, and PGRP-SA, the peptidoglycan receptor of the Toll/Dif pathway, has selective affinity for different peptidoglycans. PGRP-LCx, the default peptidoglycan receptor of the Imd/Relish pathway, has strong affinity for all polymeric peptidoglycans tested and for monomeric peptidoglycan. PGRP-LCa does not have affinity for polymeric or monomeric peptidoglycan. Instead, PGRP-LCa can form heterodimers with LCx when the latter is bound to monomeric peptidoglycan. Hence, PGRP-LCa can be said to function as an adaptor, thus adding a new function to a member of the PGRP family