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Activation of complement by circulating immune complexes isolated from leprosy patients.
P Tyagi1, V D Ramanathan, B K Girdhar
1Central JALMA Institute for Leprosy, Taj Ganj, Agra, India.
Summary
Immune complexes in leprosy activate complement pathways differently based on disease type. Polyethylene glycol precipitates from BL/LL leprosy and erythema nodosum leprosum efficiently activate both classical and alternative complement pathways.
Area of Science:
- Immunology
- Complement System
- Leprosy Pathogenesis
Background:
- Leprosy is a complex infectious disease with diverse clinical presentations.
- Circulating immune complexes (CICs) are implicated in the immunopathology of leprosy.
- The complement system plays a crucial role in innate and adaptive immunity and is activated in various inflammatory conditions.
Purpose of the Study:
- To investigate the complement-activating properties of CICs isolated from different leprosy patient groups.
- To determine whether CICs from various leprosy subtypes differentially activate the classical and alternative pathways of complement.
Main Methods:
- Isolation of CICs from leprosy patient sera using polyethylene glycol (PEG) precipitation.
- Assay of complement activation via both classical and alternative pathways by PEG precipitates.
- Comparison of complement activation capacity across different leprosy classifications (TT/BT, BL/LL) and clinical states (reactional vs. non-reactional).
Main Results:
- PEG precipitates from BL/LL leprosy and erythema nodosum leprosum (ENL) sera efficiently activated both classical and alternative complement pathways.
- PEG precipitates from TT/BT leprosy sera, including those in reaction, activated the alternative pathway but not the classical pathway.
- No significant differences in complement activation were observed between reactional and non-reactional states within the TT/BT and BL/LL groups.
Conclusions:
- The type of leprosy and associated immune complexes dictate the activation pattern of the complement system.
- BL/LL leprosy and ENL involve immune complexes capable of activating both major complement pathways, suggesting broader immune dysregulation.
- TT/BT leprosy involves immune complexes primarily activating the alternative complement pathway, potentially contributing to a different immunopathological profile.