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Regulation of endotoxin-induced inhibition of macrophage migration by fresh serum
Abstract:
Purified endotoxin (LPS) caused macrophage migration inhibition (MMI) in capillary tube cultures of guinea pig peritoneal macrophages in medium prepared with 15% fresh-frozen guinea pig serum. The inactivation of serum by heating at 56 degrees C for 30 min or by zymosan absorption prevented LPS-induced MMI. LPS was fully inhibitory in fresh C4-deficient guinea pig serum. Heat treatment of normal serum at 50 to 52 degrees C for 30 min to inactivate the alternate complement (C) pathway prevented or significantly decreased LPS-induced MMI, but heating C4-deficient serum at 50 to 52 degrees C for 30 min prevented LPS-MMI in all instances. These results suggest that the reaction was effected via the alternate C pathway but that some inhibition of migration was permitted via the classical C pathway, presumably due to antibodies for LPS in some normal sera. Pretreatment of normal serum with cobra venom factor decreased or prevented LPS-MMI in most instances, but similar results were obtained with C4-deficient serum. Experiments with chelated sera were unsuccessful because of the immobilization of macrophages by 10 mM ethylenediamine-tetraacetic acid and by 10 mM Mg-ethyleneglycol-bis (beta-aminoethyl)-N,N-tetraacetic acid. Low doses of concanavalin A and staphylococcal enterotoxin B and large doses of pokeweed mitogen caused MMI in "inactivated serum" medium, but MMI was enhanced in fresh serum.
Insights
Lipopolysaccharide (LPS) triggers macrophage migration inhibition (MMI) via the complement system. The alternate complement pathway is primarily involved, though the classical pathway may also contribute to LPS-induced MMI.
Area of Science:
- Immunology
- Cell Biology
- Complement System
Background:
- Lipopolysaccharide (LPS), a component of Gram-negative bacteria, is known to activate the immune system.
- Macrophage migration inhibition (MMI) is a cellular response that can be influenced by immune mediators.
- The complement system, comprising classical and alternate pathways, plays a crucial role in innate and adaptive immunity.
Purpose of the Study:
- To investigate the role of the complement system in lipopolysaccharide (LPS)-induced macrophage migration inhibition (MMI).
- To determine which complement pathway(s) are involved in LPS-mediated MMI in guinea pig macrophages.
Main Methods:
- Capillary tube cultures of guinea pig peritoneal macrophages were used to assess MMI.
- Serum inactivation by heating or zymosan absorption was performed to deplete complement activity.
- Experiments utilized fresh, heat-inactivated, and C4-deficient guinea pig sera, as well as serum treated with cobra venom factor.
Main Results:
- Purified LPS induced MMI in macrophages cultured in medium with fresh guinea pig serum.
- Inactivation of serum complement by heating or zymosan absorption prevented LPS-induced MMI.
- LPS-induced MMI was observed in C4-deficient serum, suggesting the involvement of the alternate complement pathway, but was also seen in normal serum, indicating potential classical pathway contribution.
Conclusions:
- The alternate complement pathway is the primary mediator of LPS-induced macrophage migration inhibition.
- The classical complement pathway may also contribute to LPS-MMI, potentially through antibodies present in normal sera.
- These findings elucidate the specific roles of complement pathways in LPS-mediated cellular immune responses.
