Platelet-activating factor, PAF acetylhydrolase, and severe anaphylaxis.

Area of Science:

• Immunology
• Allergy Research
• Biochemistry

Background:

• Platelet-activating factor (PAF) is a known mediator of anaphylaxis in animal models.
• Interventions targeting PAF have successfully prevented fatal anaphylaxis in animals.
• The specific roles of PAF and its inactivating enzyme, PAF acetylhydrolase, in human anaphylaxis remain largely uncharacterized.

Purpose of the Study:

• To investigate the association between serum Platelet-activating factor (PAF) levels and PAF acetylhydrolase activity in human patients experiencing anaphylaxis.
• To determine the correlation between PAF levels, PAF acetylhydrolase activity, and the severity of anaphylaxis, including fatal cases.
• To explore the potential role of PAF and PAF acetylhydrolase in the pathophysiology of human anaphylaxis.

Main Methods:

• Serum samples were collected from 41 patients diagnosed with anaphylaxis and 23 healthy control subjects.
• Measurements included serum PAF levels and PAF acetylhydrolase activity.
• Additional analysis compared PAF acetylhydrolase activity in patients with fatal peanut anaphylaxis against various control groups, including non-allergic individuals and those with mild or non-fatal allergic reactions.

Main Results:

• Patients with anaphylaxis exhibited significantly higher mean serum PAF levels compared to control groups, with levels correlating directly with anaphylaxis severity (P<0.001).
• A significant inverse correlation was observed between serum PAF levels and PAF acetylhydrolase activity (P<0.001).
• Lower PAF acetylhydrolase activity was increasingly prevalent with greater anaphylaxis severity and was significantly diminished in patients with fatal peanut anaphylaxis compared to all control groups (P<0.001).

Conclusions:

• Serum PAF levels are directly correlated with anaphylaxis severity in humans.
• Decreased PAF acetylhydrolase activity is inversely correlated with anaphylaxis severity and is notably low in fatal cases.
• Impaired inactivation of PAF by reduced PAF acetylhydrolase activity may be a contributing factor to the severity and lethality of human anaphylaxis.