Hypersensitivity to foods among birch pollen-allergic patients. Immunochemical inhibition studies for evaluation of possible mechanisms.

Several statistical investigations have indicated that an immunological partial identity might exist between birch pollen an some foods because of the existence of concurrent hypersensitivity symptoms to both sources. In order to study this, two groups of BP (birch pollen)-allergic patients (20 with (F+) and 20 without (F-) food hypersensitivity) were skin prick tested with extracts of various foods prepared in different ways. Sera from these patients were inhibited with different foods, including a lectin, Con A (concanavalin A), before analysis in BP-RAST and -CRIE. Corresponding experiments using sera from grass pollen allergics were performed as controls. The two groups of patients showed identical skin reactivities to BP extract whereas the F+ patients bound twice as much BP-specific IgE in RAST and CRIE as the F- patients. BP-RAST performed with sera from F+ patients were in some cases inhibited with foods and Con A; corresponding BP-CRIE were not. Neither BP-RAST (with one exception) nor -CRIE performed with sera from F- patients were inhibited with foods and Con A. TP (timothy pollen)-RAST performed with sera from timothy allergic patients were inhibited with some foods and with Con A; corresponding TP-CRIE were not. Controls performed on sera from normal individuals revealed no inhibition at all in the BP and TP systems. As no direct evidence for immunological partial identity was found from these results the clinical hypersensitivity against some foods among BP-allergics are discussed particularly regarding content of lectin in foods and common carbohydrate components in pollen allergens and food molecules.