Opsonic requirements for phagocytosis of Borrelia hermsii by human polymorphonuclear leukocytes

Area of Science:

• Immunology
• Microbiology
• Cell Biology

Background:

• Phagocytosis by human polymorphonuclear leukocytes (PMNLs) is crucial for clearing bacterial infections.
• Borrelia hermsii causes relapsing fever, and understanding its interaction with host immune cells is vital.

Purpose of the Study:

• To investigate the opsonic requirements for phagocytosis of Borrelia hermsii by human PMNLs.
• To elucidate the roles of complement pathways and immunoglobulins in spirochete clearance.

Main Methods:

• Utilized 3H-labeled Borrelia hermsii to quantify phagocytosis.
• Employed electron microscopy and cinephotomicroscopy for intracellular localization.
• Assessed phagocytosis using pooled human serum and immune/preimmune rabbit serum, including immunoabsorption.

Main Results:

• Phagocytosis increased with higher serum concentrations and spirochete-to-PMNL ratios.
• Classical complement pathway activity did not significantly affect phagocytosis.
• Immune rabbit serum enhanced phagocytosis and directly reduced spirochete motility and viability.
• Immunoabsorption of immunoglobulins abolished both direct and opsonic activities of immune serum.

Conclusions:

• Suggests a significant role for the alternative complement pathway in opsonizing Borrelia hermsii for PMNL phagocytosis.
• Highlights the importance of immunoglobulins in both opsonization and direct clearance of spirochetes.
• Indicates that PMNLs are important in controlling Borrelia hermsii infections.