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Pepsin like enzyme in macrophages and its role in the immune system
Abstract:
Phagocytosis by DBA/2 or autoimmune NZB mouse macrophages of sheep erythrocytes, which are heterologous to these macrophages, was enhanced by mouse pepsin, whereas phagocytosis of homologous erythrocytes was suppressed by pepsin. Antibody production by DBA/2 or NZB mouse lymphocytes against heterologous erythrocytes was also enhanced by pepsin, but autoantibody production by NZB mouse lymphocytes was suppressed by pepsin. An acid protease present in macrophages was found to have biochemical properties quite close to those of pepsin, with regard to molecular weight, isoelectric point, and 50% inhibition dose of pepstatin. This acid protease was immunochemically identical with pepsin, reacting with anti-pepsin antibody. Taken together, these results indicate that pepsin modulates macrophage functions and that the pepsin like enzyme in macrophages may play important roles in the regulation of phagocytosis by macrophages and in antibody production.
Insights
Mouse pepsin enhances the phagocytosis of foreign cells and antibody production by immune cells. However, it suppresses the uptake of self-cells and the production of autoantibodies, suggesting pepsin regulates immune responses.
Area of Science:
- Immunology
- Cell Biology
- Biochemistry
Background:
- Macrophages play a crucial role in the immune system through phagocytosis.
- Pepsin is an enzyme typically found in the stomach, but its role in immune cells is less understood.
- Autoimmune diseases involve the immune system attacking the body's own tissues.
Purpose of the Study:
- To investigate the effect of mouse pepsin on macrophage phagocytosis and lymphocyte antibody production.
- To determine if macrophages possess an endogenous enzyme similar to pepsin.
- To elucidate the role of pepsin in modulating immune responses, including autoimmunity.
Main Methods:
- Assessing phagocytosis of sheep erythrocytes by DBA/2 and NZB mouse macrophages in the presence of mouse pepsin.
- Measuring antibody production by DBA/2 and NZB mouse lymphocytes against heterologous erythrocytes and autoantibodies using pepsin.
- Biochemical characterization (molecular weight, isoelectric point, pepstatin inhibition) and immunochemical analysis (using anti-pepsin antibody) of a macrophage acid protease.
Main Results:
- Mouse pepsin enhanced the phagocytosis of heterologous erythrocytes by macrophages but suppressed homologous erythrocyte uptake.
- Pepsin boosted antibody production against foreign erythrocytes but inhibited autoantibody production by lymphocytes.
- A macrophage acid protease exhibited biochemical and immunochemical properties identical to pepsin.
Conclusions:
- Pepsin significantly modulates macrophage functions, affecting phagocytosis of self and non-self targets.
- An endogenous pepsin-like enzyme within macrophages may be a key regulator of phagocytosis and antibody production.
- These findings suggest a novel role for pepsin in immune regulation and potentially in autoimmune processes.