An inhibitory activity for an erythrocyte intermediate bearing the properdin (P)-stabilized amplification C3 convertase, PC3bBb, was recognized in whole normal human serum and separated from C3b inactivator by its distinct physicochemical and functional characteristics. The inhibitory activity was found to reside in a protein that was purified to homogeneity and elicited a monospecific antibody in a rabbit. This protein was identified as P11H and found to have a serum concentration of 516 + 89 yg/ml (mean ±1 SD The complement system, which is comprised of at least 18 plasma proteins, consists of four functional divisions: two pathways for activation, the classical and alternative (properdin); a single amplification mechanism that is recruited by each activating pathway; and a final common effector pathway to which the activating and amplifying sequences are directed and from which are derived the biologic activities of complement (1, 2). Activation of the classical pathway by antigenantibody complexes containing immunoglobulin of the appropriate class involves conversion of C1 from its precursor form to an active state, C1 (3), with subsequent cleavage of C4 (4) and C2 to form C4b2a (5), the classical C3 convertase that initiates cleavage of C3. Activation of the alternative pathway occurs with certain microbial polysaccharides that interact with B, D, C3, and other proteins to achieve initial CS cleavage (6).The major cleavage fragment of CS, C3b, generated by either activating sequence, then interacts with B and D (7) to form the amplification convertase, C3bBb (8, 9).Abbreviations: P, activated properdin; PC3bBb, properdin-stabilized amplification CS convertase; C3NeF, CS nephritic factor; CMbINA, C3b inactivator; DGVB++, half-isotonic Veronal-buffered saline, 0.1% gelatin, 0.5 mM magnesium, 0.15 mM calcium, and 2.5% dextrose; DGVB-EDTA, half-isotonic Veronal-buffered saline, 0.1% gelatin, 0.01 M EDTA, and 2.5% dextrose; C-EDTA, rat serum diluted 1:20 in Veronal-buffered saline, 0.1% gelatin and 0.04 M EDTA. * To whom reprint requests should be addressed.In the amplification step, C3b serves as a receptor for B (9) in a magnesium-dependent binding reaction'that partially reveals the proteolytic site in B for C3 (10). D, a protease of the serine esterase class (11), cleaves bound B to release the Ba fragment and to uncover fully the CS-cleaving site on Bb which remains bound. The C3bBb complex is labile because of irreversible decay-dissociation of Bb, but can be regenerated on the residual C3b by the uptake of additional B and its cleavage by D (9). Activated properdin (P) binds to C3b (12-14), and CS nephritic factor (C3NeF), a serum protein found in some patients with hypocomplementemic membranoproliferative glomerulonephritis, binds to C3bBb (15); both proteins stabilize the convertase and increase its half-life by as much as 10-fold, thereby profoundly augmenting amplification of CS cleavage (12,16).Control of the amplification pathway is regulated by the inherent lability of the C3bBb convertase...

Objective. The effect of chimeric anti-tumor necrosis factor a (TNFa) monoclonal antibody (MAb) therapy on synovial inflammation was studied in order to address the hypothesis that anti-TNFa therapy leads to down-regulation of adhesion molecules and a decrease in inflammatory cell influx in synovial tissue (ST).Methods. The immunohistologic features of synovial biopsy specimens, both before and 4 weeks after anti-TNFa MAb (cA2) therapy, were studied in 14 patients with rheumatoid arthritis (RA). The patients either received a placebo (n = 2), or were given intravenous doses of cA2 at 10 mg/kg (n = 5) or 20 mglkg (n = 7).Results. A significant (P < 0.03) reduction in the mean scores for T cells and for the adhesion molecules, vascular cell adhesion molecule 1 and E-selectin, was observed after therapy with 10 mg/kg or 20 mglkg of cA2 in RA patients. molecules, and the decrease in cellularity of rheumatoid ST after cA2 administration support the hypothesis that the antiinflammatory effect of anti-TNFa therapy might be partly explained by down-regulation of cytokineinducible vascular adhesion molecules in ST, with a consequent reduction of cell traffic into joints. Conclusion. The reduced expression of adhesion

The presence of activated T cells in the synovial membrane of patients with rheumatoid arthritis (RA) suggests a role for these cells in the pathogenesis of the disease. Recent evidence indicates that human T cells may fall into functional categories dependent on their cytokine profile and cytotoxic capacity. The human Th1 subset is cytolytic and produces high levels of IFN-gamma whereas the Th2 type of T cell produces IL-4. In order to investigate whether Th1 or Th2 type cells are present in the inflammatory synovial membrane in RA, a panel of synovial membrane derived T-cell clones (n = 19) was generated and studied functionally. Anti-CD3-induced cytotoxicity assays were performed to demonstrate the cytotoxic potential of clones. Except for two, all clones were cytolytic in this test. Clone cells were activated to initiate cytokine production and assessment of the cytokine levels showed that all clones produced large amounts of IFN-gamma (18 out of 19 clones: over 50,000 pg/ml) whereas IL-4 was absent or present in minimal amounts (17 out of 19 clones: less than 1000 pg/ml). The production of IL-1, IL-2 and IL-6 was variable. The functional characteristics of the clones studied indicate that they may resemble the Th1 subtype of T cells. Our data suggest a relation between Th1-type functions the chronic inflammation characteristic of RA.

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Objective. To define the expression and the phenotype of granzyme (Gran) A and B positive cytotoxic cells in synovial tissue (ST) from patients with rheumatoid arthritis (RA) with respect to disease duration and activity. Methods. Using antibodies against GranA and GranB, which serve as markers of activated natural killer (NK) cells and cytotoxic T lymphocytes, ST sections from 10 patients with early RA, 10 patients with longstanding RA, and 10 patients with osteoarthritis were examined. The phenotype of Gran+ cells was determined with double‐labeling techniques. Results. Gran+ cells, the majority of which were NK cells, were found in ST from patients in all groups. Several of these cells did not express the surface markers CD16, CD56, and CD57. The highest ST expression of GranB was found in patients with early RA. In RA patients, there was a positive correlation of GranB expression with serum levels of acute‐phase reactants, but not with histologic scores for inflammation. Conclusion. Gran+ cells are mainly NK cells, a substantial proportion of which do not express conventional NK cell surface markers. GranB expression is specifically increased in the synovial tissues of patients with RA of short duration.