Related Experiment Video
Updated: Jul 29, 2025
Investigation of Macrophage Polarization Using Bone Marrow Derived Macrophages
Published on: June 23, 2013
Macrophage polarization during Streptococcus agalactiae infection is isolate specific
Larisa Janžič1, Jernej Repas2, Mojca Pavlin2,3
1Department of Cell Immunology, Institute of Microbiology and Immunology, Faculty of Medicine, University of Ljubljana, Ljubljana, Slovenia.
Introduction:
Streptococcus agalactiae (Group B Streptococcus, GBS), a Gram-positive commensal in healthy adults, remains a major cause of neonatal infections, usually manifesting as sepsis, meningitis, or pneumonia. Intrapartum antibiotic prophylaxis has greatly reduced the incidence of early-onset disease. However, given the lack of effective measures to prevent the risk of late-onset disease and invasive infections in immunocompromised individuals, more studies investigating the GBS-associated pathogenesis and the interplay between bacteria and host immune system are needed.
Methods:
Here, we examined the impact of 12 previously genotyped GBS isolates belonging to different serotypes and sequence types on the immune response of THP-1 macrophages.
Results:
Flow cytometry analysis showed isolate-specific differences in phagocytic uptake, ranging from 10% for isolates of serotype Ib, which possess the virulence factor protein β, to over 70% for isolates of serotype III. Different isolates also induced differential expression of co-stimulatory molecules and scavenger receptors with colonizing isolates inducing higher expression levels of CD80 and CD86 compared to invasive isolates. In addition, real-time measurements of metabolism revealed that macrophages enhanced both glycolysis and mitochondrial respiration after GBS infection, with isolates of serotype III being the most potent activators of glycolysis and glycolytic ATP production. Macrophages also showed differential resistance to GBS-mediated cell cytotoxicity as measured by LDH release and real-time microscopy. The differences were evident both between serotypes and between isolates obtained from different specimens (colonizing or invasive isolates) demonstrating the higher cytotoxicity of vaginal compared with blood isolates.
Conclusions:
Thus, the data suggest that GBS isolates differ in their potential to become invasive or remain colonizing. In addition, colonizing isolates appear to be more cytotoxic, whereas invasive isolates appear to exploit macrophages to their advantage, avoiding the immune recognition and antibiotics.
Insights
Group B Streptococcus (GBS) isolates vary in their ability to cause invasive infections. Colonizing GBS strains are more cytotoxic, while invasive strains evade immune responses by exploiting macrophages.
Area of Science:
- Immunology
- Microbiology
- Infectious Diseases
Background:
- * Streptococcus agalactiae* (Group B *Streptococcus*, GBS) is a significant cause of neonatal infections, including sepsis, meningitis, and pneumonia.
- * While intrapartum antibiotic prophylaxis reduces early-onset disease, effective prevention of late-onset disease and infections in immunocompromised individuals remains a challenge.
- * Further research into GBS pathogenesis and host-pathogen interactions is crucial.
Purpose of the Study:
- * To investigate the impact of different GBS isolates on macrophage immune responses.
- * To analyze isolate-specific differences in phagocytosis, immune cell activation, metabolism, and cytotoxicity.
- * To understand how GBS serotypes and origins (colonizing vs. invasive) influence host immune evasion.
Main Methods:
- * Genotyped 12 GBS isolates from various serotypes and sequence types.
- * Assessed macrophage phagocytic uptake using flow cytometry.
- * Measured co-stimulatory molecule (CD80, CD86) and scavenger receptor expression.
- * Analyzed macrophage glycolysis and mitochondrial respiration in real-time.
- * Quantified GBS-mediated cytotoxicity via LDH release and real-time microscopy.
Main Results:
- * Significant isolate-specific variations in phagocytic uptake, with serotype III isolates showing over 70% uptake and serotype Ib isolates showing 10%.
- * Colonizing GBS isolates induced higher CD80/CD86 expression compared to invasive isolates.
- * GBS infection enhanced macrophage glycolysis and mitochondrial respiration, with serotype III isolates being potent activators.
- * Macrophages exhibited differential resistance to GBS cytotoxicity, with vaginal isolates being more cytotoxic than blood isolates.
Conclusions:
- * GBS isolates exhibit distinct potentials for invasiveness versus colonization.
- * Colonizing GBS isolates demonstrate higher cytotoxicity, potentially contributing to their clearance.
- * Invasive GBS isolates appear adept at exploiting macrophages, facilitating immune evasion and antibiotic resistance.
More Related Videos
Related Concept Videos
01:25Immune Surveillance by NK Cells and Phagocytes
Natural Killer Cells: The Fast Responders
NK cells are large granular lymphocytes found in the blood and lymphatic system. These...
01:31Defense Against Bacterial Pathogens
Phagocytes
Phagocytes are the frontline soldiers of the immune system. They include neutrophils and macrophages. Neutrophils are the most abundant type of white blood cell and are quickly mobilized to the site of infection. Macrophages are larger cells that patrol...