Interaction of mediators and effector cells in cashew nut-induced anaphylaxis

The underlying mechanisms of an immediate food-induced allergic reaction involve mast cell degranulation and recruitment of other effector cells, such as lymphocytes, eosinophils, and basophils. How the interaction of various mediators and cells results in anaphylaxis is not fully understood.

To evaluate changes in platelet-activating factor (PAF), platelet-activating factor acetylhydrolase (PAF-AH), tryptase, eosinophils, basophils, and eosinophil cationic protein (ECP) in cashew nut-induced anaphylaxis.

Open cashew nut challenges were performed on 106 children (aged 1-16 years), sensitized to cashew nut, with earlier allergic reaction to cashew nut or no known exposure. PAF, PAF-AH, tryptase, ECP, eosinophils, and basophils were measured at 4 time points.

Of 72 challenges with positive results, 34 were defined as anaphylactic. Eosinophil count decreased progressively during an anaphylactic reaction at all 4 time points (P < .005*) compared with baseline. Although significant PAF elevation was observed 1 hour from moderate-to-severe reaction (P = .04*), PAF seemed to peak especially in anaphylaxis but did not achieve statistical significance. PAF peak ratio (peak PAF/baseline PAF) was significantly greater in anaphylactic reactions compared with the no-anaphylaxis group (P = .008*). Maximal percentage change in eosinophils revealed negative correlation to severity score and PAF peak ratio (Spearman's rho -0.424 and -0.516, respectively). Basophils decreased significantly in moderate-to-severe reactions and in anaphylaxis (P < .05*) compared with baseline. Delta-tryptase (peak tryptase minus baseline) did not differ significantly between anaphylaxis and the no-anaphylaxis subgroups (P = .05).

PAF is a specific anaphylaxis biomarker. Marked decline of eosinophils during anaphylaxis may be related to robust secretion of PAF reflecting migration of eosinophils to target tissues.