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Serum complement profile in human leprosy and its comparison with immune complex diseases
Insights
Leprosy patients show significant complement component C3 consumption primarily via the alternate pathway, likely initiated by aggregated immunoglobulins in cryoprecipitates. Further research is needed on later complement components in leprosy.
Area of Science:
- Immunology
- Complement System
- Infectious Diseases
Background:
- Leprosy, a complex infectious disease, involves immune system dysregulation.
- The complement system plays a crucial role in immune responses and host defense.
- Understanding complement activation pathways in leprosy is vital for elucidating disease pathogenesis.
Purpose of the Study:
- To investigate serum levels of complement components in leprosy patients.
- To compare complement profiles in tuberculoid and lepromatous leprosy with healthy controls and other immune complex diseases.
- To analyze the role of complement activation pathways and cryoglobulins in leprosy.
Main Methods:
- Serum samples from leprosy patients (tuberculoid and lepromatous) and controls were analyzed.
- Levels of early, middle, and distal complement components (Clq, C3, C4, C5, C8, C9), C1-inactivator, and CH50 were measured.
- Cryoglobulins were identified and characterized (IgG, IgA, IgM, fibrinogen).
- Serum factor B and its breakdown product (Ba) were studied.
Main Results:
- Significant C3 complement consumption was observed in leprosy patients.
- C3 consumption appears to occur primarily via the alternate pathway, unlike the direct pathway seen in lupus nephritis.
- Aggregated immunoglobulins in cryoprecipitates likely initiate alternate pathway activation.
- Cryoglobulins consisted mainly of IgG, IgA, IgM, or fibrinogen.
Conclusions:
- Complement component C3 consumption in leprosy is predominantly mediated by the alternate pathway.
- Aggregated immunoglobulins in cryoprecipitates are implicated as initiators of this complement activation.
- The specific roles of middle and distal complement components (C5, C8, C9) in leprosy-associated complement consumption require further investigation.
Abstract:
In the present study we have estimated the serum levels of early, middle, and distal complement components, e.g., Clq, C3, C4, C5, C8, and C9 along with C1-inactivator and CH50 in patients with tuberculoid and lepromatous leprosy and have compared these results with the levels in healthy subjects as well as with levels in patients with other immune complex diseases. We have also analyzed the cryoglobulins present in the sera of these patients; they consisted of either a single or mixed IgG, IgA, IgM or fibrinogen in most instances. The component C3 was found in only one sample. It appears that unlike lupus nephritis, in which complement is activated by direct path in which complement is activated by direct path in about 30% to 50% of leprosy patients, significant C3 complement consumption takes place primarily via the alternate pathway and is probably initiated by the aggregated immunoglobulins represented in cryoprecipitates. This is further supported by the study of serum factor B and its breakdown product (Ba) in these patients. The question of the role of the middle and distal complement components, such as C5, C8 and C9, during total hemolytic complement and C3 consumption in leprosy remains unanswered.