Effects of fibronectin on the interaction of polymorphonuclear leukocytes with unopsonized and antibody-opsonized...

Area of Science:

• Immunology
• Cell Biology
• Microbiology

Background:

• Polymorphonuclear leukocytes (PMNLs) are critical immune cells involved in bacterial clearance.
• Fibronectin (Fn) is an extracellular matrix protein known to modulate cell interactions.
• The role of Fn in PMNL-bacterial interactions and subsequent immune responses requires further elucidation.

Purpose of the Study:

• To investigate the effect of Fibronectin (Fn) on polymorphonuclear leukocyte (PMNL) interactions with various bacteria.
• To determine the impact of Fn on bacterial uptake, intracellular killing, and PMNL respiratory burst.
• To elucidate the intracellular or extracellular mechanisms underlying Fn-mediated enhancement of PMNL activity.

Main Methods:

• Chemiluminescence (CL) assay to measure PMNL respiratory burst activity.
• Acridine orange-crystal violet monolayer assay to assess bacterial ingestion and intracellular killing by PMNLs.
• Use of specific inhibitors (NaN3) and scavengers (superoxide dismutase, human serum albumin) to probe cellular mechanisms.

Main Results:

• Fn alone enhanced PMNL chemiluminescence and killing of Staphylococcus aureus and Staphylococcus epidermidis.
• Fn did not enhance PMNL responses to Group B Streptococcus (GBS) or Escherichia coli unless bacteria were antibody-opsonized.
• Fn-enhanced chemiluminescence was inhibited by NaN3, suggesting an intracellular mechanism involving the respiratory burst.

Conclusions:

• Fibronectin significantly enhances PMNLs' interaction with and killing of certain bacteria, particularly Staphylococcus species.
• Antibody opsonization is crucial for Fn to enhance PMNL responses to GBS and E. coli.
• The observed enhancement of PMNL activity by Fn is primarily an intracellular event mediated by the respiratory burst.