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Studies on the inhibition of macrophage migration induced by soluble antigen-antibody complexes
Abstract:
Mixtures of serum of Freund's complete adjuvant (FCA) immunized guinea-pigs and tuberculin PPD consistently inhibited the in vitro migration of peritoneal exudate cells (PEC) of normal guinea-pigs. It is shown that this inhibitory effect is due to a soluble complex between an IgG2 antibody and PPD. By separation of PPD on Sephadex G-200 two peaks were obtained, corresponding respectively to molecular weights of at least 800,000 and 25,000, separated by a plateau. Material derived from both peaks and from the plateau was able to form inhibitory complexes with anti-PPD IgG2. When a mixture of small molecular weight PPD and anti-PPD IgG2 was fractionated on Sephadex G-200, the inhibitory activity was recovered in the void region only. The detection of both IgG2 and PPD in the latter was taken as evidence for the presence of a high molecular weight antigen-antibody complex. When the mechanism of complex-induced inhibition of migration was examined it was found that: (1) complexes act directly on macrophages present in the peritoneal exudate; (2) removal of the Fc fragment of IgG2 by pepsin abolishes its ability to form migration inhibitory complexes; (3) passive sensitization of macrophages with anti-PPD IgG2, followed by exposure to PPD does not result in inhibition of migration; (4) in order to obtain migration inhibition, the complexes must be present during the entire migration period. A 2-hr pulse with complexes does not induce permanent inhibition; (5) the migration inhibitory activity of antigen--antibody complexes can be abolished by certain concentrations of puromycin and aminophylline.
Insights
Immune complexes formed between antibodies and tuberculin PPD inhibit macrophage migration. This effect requires intact IgG2 antibodies and continuous presence of the complex during migration for inhibition.
Area of Science:
- Immunology
- Cellular immunology
Background:
- Freund's complete adjuvant (FCA) immunization in guinea-pigs elicits immune responses.
- Tuberculin Purified Protein Derivative (PPD) is a key antigen in tuberculosis diagnostics and research.
- Peritoneal exudate cells (PEC) are commonly used to study cellular immune responses in vitro.
Purpose of the Study:
- To investigate the mechanism by which serum from immunized guinea-pigs inhibits the migration of normal peritoneal exudate cells (PEC).
- To identify the components responsible for the migration inhibition.
- To elucidate the characteristics of the antigen-antibody complex involved in this phenomenon.
Main Methods:
- In vitro migration inhibition assays using guinea-pig PEC.
- Fractionation of tuberculin PPD using Sephadex G-200 chromatography.
- Characterization of antigen-antibody complexes using molecular weight separation.
- Enzymatic treatment (pepsin digestion) to remove Fc fragments from IgG2 antibodies.
Main Results:
- Serum from FCA-immunized guinea-pigs containing anti-PPD IgG2 antibodies formed soluble complexes with PPD, inhibiting PEC migration.
- The inhibitory activity was associated with high molecular weight antigen-antibody complexes.
- Complexes acted directly on macrophages, and the Fc fragment of IgG2 was essential for inhibition.
- Continuous presence of complexes during migration was necessary; short exposure did not cause permanent inhibition.
- Migration inhibition could be reversed by puromycin and aminophylline.
Conclusions:
- Soluble antigen-antibody complexes, specifically involving IgG2 and PPD, are responsible for inhibiting macrophage migration.
- The Fc portion of the IgG2 antibody plays a critical role in mediating this inhibitory effect.
- The findings provide insights into the cellular mechanisms of delayed-type hypersensitivity and immune complex-mediated responses.