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Role of antibody and complement in the control of Encephalitozoon cuniculi infections by rabbit macrophages
Abstract:
The capacity of mononuclear peritoneal macrophages to phagocytose Encephalitozoon cuniculi was tested in vitro. Normal rabbit serum or cell culture medium had little effect on the rate of removal of organisms by rabbit peritoneal macrophages. Treatment with immune rabbit serum or immune rabbit immunoglobulin G significantly (P less than 0.001) increased phagocytosis of E. cuniculi. Guinea pig complement was found to significantly (P less than 0.001) enhance the phagocytosis of antibody-treated E. cuniculi. With few exceptions, induced (peritoneal exudate) macrophages were no more effective than unstimulated (resident) macrophages in the phagocytosis of E. cuniculi. Secondary lysosomes labeled with ferritin were seen fusing with phagosomes containing immune rabbit serum-treated parasites. Phagosome-lysosome fusion was not observed when parasites were treated with either normal rabbit serum or culture medium. The results of the present study suggest a role for antibody enhancement of phagocytosis and intracellular killing as a mechanism of resistance to encephalitozoonosis in rabbits.
Insights
Immune rabbit serum significantly boosted the ability of rabbit macrophages to engulf Encephalitozoon cuniculi. Complement further enhanced this phagocytosis, suggesting a key role for antibodies in fighting encephalitozoonosis.
Area of Science:
- Immunology
- Cell Biology
- Parasitology
Background:
- Encephalitozoon cuniculi is an intracellular parasite that causes disease in various animals.
- Phagocytosis by macrophages is a critical component of the host immune response to parasitic infections.
- The role of specific immune components in macrophage phagocytosis of E. cuniculi requires further elucidation.
Purpose of the Study:
- To investigate the in vitro phagocytic capacity of rabbit mononuclear peritoneal macrophages against Encephalitozoon cuniculi.
- To determine the effect of normal and immune rabbit serum, immunoglobulin G, and complement on E. cuniculi phagocytosis.
- To compare the phagocytic efficiency of resident versus induced macrophages.
Main Methods:
- In vitro phagocytosis assay using rabbit peritoneal macrophages and Encephalitozoon cuniculi.
- Treatment of E. cuniculi with normal rabbit serum, immune rabbit serum, immune rabbit immunoglobulin G, and guinea pig complement.
- Assessment of phagocytosis rates and observation of phagosome-lysosome fusion using ferritin-labeled secondary lysosomes.
Main Results:
- Immune rabbit serum and immune rabbit immunoglobulin G significantly increased E. cuniculi phagocytosis by macrophages (P < 0.001).
- Guinea pig complement significantly enhanced the phagocytosis of antibody-treated E. cuniculi (P < 0.001).
- No significant difference in phagocytic capacity was observed between induced and resident macrophages.
- Phagosome-lysosome fusion was observed with antibody-treated parasites, but not with parasites treated with normal serum or medium.
Conclusions:
- Antibody opsonization plays a crucial role in enhancing macrophage phagocytosis of Encephalitozoon cuniculi.
- Complement acts synergistically with antibodies to promote phagocytosis of E. cuniculi.
- These findings suggest that antibody-mediated phagocytosis and intracellular killing are important mechanisms for resistance to encephalitozoonosis in rabbits.