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Role of filter-bound IgA in inhibiting polymorphonuclear leukocyte chemotaxis
Abstract:
The effects of human serum IgA on human polymorphonuclear leukocyte (PMN) function were studied. In Boyden chambers, chemotactic migration against semipurified C5a as well as the formylated tripeptide FMLP was inhibited in the presence of IgA. Under such conditions, the release of superoxide anion was not changed. In addition, chemotaxis "under agarose" using the leading front evaluation remained unaltered in the presence of IgA despite IgA-induced aggregation of PMN and reduced density of migrating cells. Chemotaxis filters incubated with radiolabelled IgA demonstrated strong binding of IgA, and further, these IgA-pretreated filters impeded PMN migration. Incubation of PMN with IgA followed by subsequent washings did not affect chemotactic migration. These data show that filter binding of IgA is responsible for the inhibition of chemotactic PMN-migration in the Boyden chambers, most probably mediated by increased cell-substrate adhesion. Experiments using casein showed displacement of IgA by casein which enables PMN to fully respond to casein.
Insights
Human serum immunoglobulin A (IgA) inhibits polymorphonuclear leukocyte (PMN) migration by binding to filters, not by affecting cell function directly. This IgA binding increases cell-substrate adhesion, hindering PMN movement.
Area of Science:
- Immunology
- Cell Biology
Background:
- Polymorphonuclear leukocytes (PMNs) are crucial immune cells.
- Immunoglobulin A (IgA) is a key antibody in mucosal immunity.
Purpose of the Study:
- To investigate the effects of human serum IgA on human PMN function, specifically chemotaxis.
- To elucidate the mechanism behind IgA's influence on PMN migration.
Main Methods:
- Chemotaxis assays using Boyden chambers and the
- under agarose
- method.
- Radiolabelled IgA to assess filter binding.
- Superoxide anion release assays.
- PMN aggregation assessment.
Main Results:
- Human serum IgA inhibited PMN chemotactic migration in Boyden chambers.
- IgA binding to chemotaxis filters impeded PMN migration, suggesting increased cell-substrate adhesion.
- IgA did not affect superoxide anion release or chemotaxis in the
- under agarose
- assay.
- Casein could displace IgA, restoring PMN chemotaxis.
Conclusions:
- Filter binding of IgA, not direct interaction with PMNs, is responsible for inhibiting chemotaxis in Boyden chambers.
- Increased cell-substrate adhesion mediated by IgA binding likely causes the observed inhibition.
- These findings highlight the importance of IgA's interaction with surfaces in modulating immune cell function.