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Background Platelet-activating factor (PAF) is a highly potent phospholipid mediator responsible for the life-threatening manifestations of anaphylaxis. PAF acetylhydrolase (PAF-AH) inactivates PAF and protects against severe anaphylaxis whereas deficiency of PAF-AH predisposes to severe or fatal anaphylaxis. Determinants of PAF-AH activity have not been studied in patients with peanut allergy. Objectives To determine whether plasma PAF-AH activity in patients with peanut allergy is related to formation of circulating complexes with apolipoprotein B (apoB) the main surface protein on low density lipoprotein particles. Methods Plasma PAF-AH activity and apoB concentrations were measured in 63 peanut allergic patients (35 boys, 28 girls, ages 2 - 19 years). ApoB concentration was measured immunoturbidimetrically using goat anti-human apoB. The correlation between PAF-AH activity and apoB concentration was determined. Results A positive correlation was found between PAF-AH activity and apoB concentration (r² = 0.59, P < 0.0001). Conclusion In peanut allergic patients, PAF-AH activity strongly correlates with apoB concentration, suggesting the presence of circulating PAF-AH- lipoprotein complexes. [ABSTRACT FROM AUTHOR]

Highlights: [•] IL-1β induces a time dependent synthesis of intracellular PAF in U-937. [•] The last enzymes of both biosynthetic routes of PAF are activated by IL-1β. [•] PAF-AH is crucial for the maintenance of intracellular PAF levels in U-937. [ABSTRACT FROM AUTHOR]