Therefore, arthritis of mid-range intensity (mean clinical index of 6C8) is usually often optimal. synovial sublining, where they reside near blood vessels, fascial planes, and within nerves (2). In autoimmune inflammatory arthritis and osteoarthritis, mast cells can expand in number by ten-fold or more, most likely via maturation of resident or newly-recruited mast cell progenitors originating from the bone marrow (2, 3). Mast cells thereby become an impressive histological feature of the inflamed synovium (Physique 1), and identifying their role is an important task for AZD1080 the synovial biologist. Open in a separate window Physique 1. Human RA synovium stained for tryptase (red) highlights abundance of mast cells in chronically inflamed joint tissue; reproduced from reference (2). Multiple systems are available for induction of experimental arthritis (4). Most of these can be grouped into two categories. The first category consists of models in which mice develop systemic autoimmunity that then translates into joint inflammation. One AZD1080 example is K/BxN arthritis, in which KRN mice around the C57Bl/6 genetic background (therefore K/B) bearing a transgenic T cell receptor are crossed to NOD mice expressing a specific MHC II (I-Ag7). F1 mice from this cross (K/BxN) spontaneously develop high-titer IgG antibodies against the glycolytic enzyme glucose-6-phosphate isomerase (GPI), and arthritis develops principally through the action of these autoantibodies (5C7). A similar sequence of events occurs in collagen-induced arthritis (CIA), a model in which DBA/1 mice immunized with type II collagen develop joint-specific autoimmunity (8). Arthritis in these systems reflects both the formation of the adaptive immune response and the subsequent effector-phase of joint inflammation. In most such models, antibodies represent a major pathogenic actor, the exception being arthritis in the SKG mouse strain, which can develop through the activity of autoimmune T cells in the absence of antibody (9). The second category of arthritis model reflects only the effector phase of disease, bypassing the generation of systemic autoimmunity via the adoptive transfer of arthritogenic autoantibodies. Examples are arthritis induced by anti-type II collagen antibodies (anti-collagen antibody-induced arthritis, CAIA), or by injection of autoantibody-containing serum from K/BxN mice (K/BxN serum transfer arthritis). In each of these experimental systems, a single monoclonal antibody is usually insufficient to cause disease. Rather, a cocktail of several different autoantibodies is required, likely reflecting the need for immune complex formation C i.e. both systems model IgG AZD1080 immune complex arthropathy (10). These systems have several advantages. First, formation of the autoimmune response can be taken out of the equation, affording a discrete focus AZD1080 on the effector phase of disease. Second, they are rapid, evolving within days of autoantibody transfer; an important corollary is usually that they may not model the pathogenic processes occurring in chronic, established disease such as human rheumatoid arthritis. Third, they can be induced in most strains of mice, enabling study of useful mutants, though since the intensity of resulting arthritis depends on the genetic background, care must be taken to match the background of experimental strains. Given strong evidence implicating IgG immune complexes in human autoimmune arthritis, in particular rheumatoid-factor positive rheumatoid arthritis, our studies have employed K/BxN serum transfer arthritis (11). In this model, anti-GPI antibodies are believed to target the joints either through deposition of circulating immune complexes or by formation of immune complexes in situ on GPI deposited around the cartilage surface (12). This chapter describes methods for the evaluation of the role of mast cells in murine K/BxN arthritis. Distinct ZNF384 mast cell (MC) subpopulations are situated at specific microanatomic locations. MCs have historically.