Antitoxin activity of human polymorphonuclear leucocytes

Area of Science:

• Immunology
• Microbiology
• Cell Biology

Background:

• Bacterial exotoxins pose significant health risks.
• The innate immune system, particularly white blood cells, plays a crucial role in neutralizing pathogens and their toxins.
• Polymorphonuclear leucocytes (PMNL) are key components of the innate immune response.

Purpose of the Study:

• To investigate the capacity of human polymorphonuclear leucocytes (PMNL) to inactivate specific bacterial exotoxins.
• To identify the cellular components and mechanisms responsible for PMNL's antitoxin activity.
• To determine the potential role of PMNL as a primary defense against bacterial toxins.

Main Methods:

• Incubation of PMNL (whole cells and sonicated suspensions) with Clostridium difficile cytotoxin and Clostridium perfringens toxins.
• Testing of mononuclear cell fractions for antitoxin activity.
• Sucrose density gradient fractionation of PMNL to isolate active components.
• Assessment of toxin inactivation in the presence of protease inhibitors.
• Comparison of PMNL activity with purified chymotrypsin.

Main Results:

• PMNL effectively inactivated Clostridium difficile cytotoxin and Clostridium perfringens phospholipase C, but not C. perfringens enterotoxin.
• Antitoxin activity was associated with PMNL, not mononuclear cells, and correlated with cell concentration.
• The highest PMNL concentrations completely inactivated C. difficile cytotoxin within 2 minutes.
• Fractionation localized antitoxin activity to myeloperoxidase within PMNL's primary granules.
• Protease inhibitors blocked toxin inactivation, suggesting a role for neutral proteases.
• PMNL demonstrated greater activity against C. difficile cytotoxin than purified chymotrypsin.

Conclusions:

• Human PMNL possess significant antitoxin activity against specific bacterial exotoxins, notably C. difficile cytotoxin.
• The antitoxin activity is mediated by neutral proteases located in the primary granules of PMNL.
• PMNL represent a critical component of the innate immune system's defense against certain bacterial toxins.