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Cytochemical study of Streptococcus agalactiae and macrophage interaction
C F Teixeira1, N L Azevedo, T M Carvalho
1Departamento de Biologia Celular e Genética, Universidade do Estado do Rio de Janeiro, Rio de Janeiro, Brasil.
Abstract:
Light and electron microscopy were used to analyse the process of interaction of Streptococcus agalactiae (serotypes Ia, III, and V) with resident and activated mouse peritoneal macrophages. Transmission electron microscopy showed that adherence of the S. agalactiae serotype Ia, but not III and V serotypes, to the surface of activated macrophages triggers the respiratory oxidative burst as revealed by the presence of reduced nicotinamide adenine dinucleotide (phosphate) [NAD(P)H]-oxidase in the phagocytic vacuoles. Fusion of macrophage lysosomes with bacteria-containing phagocytic vacuoles was observed in macrophages treated with Lucifer yellow as well as by localization of acid phosphatase for all serotypes.
Insights
Streptococcus agalactiae serotype Ia triggers an oxidative burst in macrophages, while all serotypes fuse with macrophage lysosomes. This study reveals differential interactions between S. agalactiae and immune cells.
Area of Science:
- Immunology
- Microbiology
- Cell Biology
Background:
- Streptococcus agalactiae (Group B Streptococcus) is a significant human pathogen.
- Macrophages are key immune cells involved in phagocytosing and clearing bacterial infections.
- Understanding bacterial-macrophage interactions is crucial for developing effective therapeutic strategies.
Purpose of the Study:
- To investigate the interaction between different serotypes of Streptococcus agalactiae (Ia, III, and V) and mouse peritoneal macrophages.
- To elucidate the cellular mechanisms involved in macrophage response to S. agalactiae infection.
Main Methods:
- Light and transmission electron microscopy were employed.
- Resident and activated mouse peritoneal macrophages were utilized.
- Specific markers like reduced nicotinamide adenine dinucleotide (phosphate) [NAD(P)H]-oxidase and acid phosphatase were localized.
Main Results:
- Serotype Ia of S. agalactiae adhered to activated macrophages and triggered the respiratory oxidative burst, indicated by NAD(P)H-oxidase presence in phagocytic vacuoles.
- Serotypes III and V did not trigger this oxidative burst upon adherence.
- Lysosomal fusion with bacteria-containing phagocytic vacuoles occurred for all tested serotypes (Ia, III, and V) in macrophages.
Conclusions:
- S. agalactiae serotype Ia exhibits a distinct interaction mechanism with macrophages compared to serotypes III and V, specifically by activating the oxidative burst.
- Despite differences in triggering the oxidative burst, all S. agalactiae serotypes are ultimately targeted by macrophage lysosomes, suggesting a common clearance pathway.
- These findings contribute to understanding the immunomodulatory roles of different S. agalactiae serotypes.