Interaction of human polymorphonuclear leukocyte elastase with human IgM In vitro production of an Fabmu-like fragment

Plasma and synovial fluid levels of granulocytal elastase-alpha-1-protease inhibitor complex in patients with rheumatoid arthritis

Plasma and synovial fluid levels and granulocytal elastase-alpha-1-protease inhibitor complex (EIC) in patients with rheumatoid arthritis (RA) were measured by enzyme-linked immunoassay and the results compared with those in patients with osteoarthrosis (OA). It was found that the plasma and synovial fluid levels of EIC in RA patients were higher than those in OA patients. There was a positive correlation between plasma EIC level in RA patients in Lansbury's index score of disease activity, as this tends to be higher when titer of RAHA in the plasma is high. The level of EIC in the synovial fluids correlated positively with granulocyte count and alpha-1-protease inhibitor (alpha-1-PI) level, and this, too, tends to be higher when titer of RAHA in synovial fluid is high. The results suggested that the level of EIC in the plasma or synovial fluids can be a good marker for the systemic or localized activation of the granulocytes and that IgM rheumatoid factor (IgMRF) is involved in the mechanism of the release of elastase.

Immunologic aspects of cystic fibrosis

Bacterial infections determine life expectancy in the hereditary disease cystic fibrosis (CF). The dominant pathogens are Staphylococcus aureus and Pseudomonas aeruginosa, which persist in the patient's respiratory tract. Current explanations of the chronicity of the infections in the apparently immunocompetent host are based on defective opsonophagocytosis. This may be caused by (1) bacterial exopolysaccharide production, leading to cryptic infection types; (2) cleavage of immunoglobulin, complement, and surface receptors on immunocompetent cells by host proteases; and (3) a change from opsonic to nonopsonic antibody isotypes. Continuous antigenic stimulation of the immune system leads to local immune complex formation and a high chronic hypersensitivity reaction as well as to temporary immune unresponsiveness. Progressive tissue damage caused by lysosomal enzymes and oxygen radicals from polymorphonuclear leukocytes is thought to be ultimately responsible for respiratory failure and death in CF. Besides antibiotic treatment, anti-inflammatory therapy is therefore currently considered beneficial.

Localization of IgA and IgM in human colostral elements using immunoelectron microscopy

In addition to the free form, IgA is associated with cellular and noncellular elements present in human colostrum. To resolve the existing controversy as to the cell type(s) containing IgA, we used immunoelectron microscopy with horseradish peroxidase-labeled F(ab')2 or Fab' fragments of anti-IgA or anti-IgM to determine the distribution of these immunoglobulins in colostral elements. IgA and IgM were localized in phagocytic vacuoles of polymorphonuclear leukocytes and macrophages in the vicinity of the cell membrane. In neutrophilic leukocytes, both immunoglobulins were occasionally found in phagocytic vacuoles distributed throughout the cytoplasm. Although the in vitro phagocytic activity of colostral cells was low, they retained the ability to ingest colloidal gold particles which were subsequently localized in phagocytic vacuoles that also contained IgA or IgM. IgA and IgM were not detected in lymphocytes, and plasma cells were not found in human colostrum. Numerous noncellular colostral globules of various shapes and sizes also contained IgA and IgM. These observations indicate that IgA and IgM were acquired by phagocytic cells and noncellular globules and were not actively synthesized by lymphoid cells present in human colostrum.

A comparative analysis of human IgM rheumatoid factor degradation by purified elastase and total granule extracts from human polymorphonuclear leukocytes

A modified digestion system using radiolabeled IgM rheumatoid factors (RF) and unlabeled IgG was used to examine IgM RF digestion by human polymorphonuclear leukocyte (PMN) elastase. Upon molecular sieve chromatography, the radioactive fragments coelute with fragments produced by elastase digestion of an IgM protein giving no RF activity. The fragments represent an Fab2-like fragment, an Fab-like fragment, and small peptides. Utilizing this same system, digests were performed at both acid and neutral pH to compare the proteolytic action of purified elastase on IgM RF (Ove) to the action of the total granule extract (TGE) from human PMN. At pH 4.5, purified elastase exhibits low-level protease activity, producing a slightly degraded IgM fragment with a molecular weight of about 800,000 daltons. In contrast, TGE at pH 4.5 completely degrades IgM RF to small peptides. At pH 7.5, the fragments produced by TGE digestion of IgM (Ove) coelute with fragments produced by elastase digestion under the same conditions. Thus elastase appears to be the major granule protease active in IgM RF degradation at the pH characterizing the inflammatory site.

Interaction of human polymorphonuclear leukocyte (PMN) elastase with human IgM. Production of a factor enhancing PMN migration in vitro

Digestion in vitro of human monoclonal IgM by human polymorphonuclear leukocyte (PMN) elastase produces small peptides in addition to larger fragments. These small peptides were shown to enhance PMN locomotion in vitro, as tested by the migration-under-agarose assay. The small peptides from elastase degradation of the Fc5u portion of the IgM molecule also increase PMN migration in vitro. The migration-enhancing factor is stable at 60 degrees C for 20 minutes but is inactivated by boiling for 10 minutes, and has a molecular weight which falls between 1,000 and 10,000 daltons.