Humoral and cell-mediated immune responses to fractions of birch pollen extract

IgE and IgG antibodies (ab) and lymphocyte transformation (LT) were studied in untreated and hyposensitized birch pollen allergic subjects and in non-atopic controls using whole extract and fractions obtained by gel filtration of birch pollen extract. All the allergic subjects had positive IgE ab, IgG ab and LT responses to the whole extract. Both the untreated and the hyposensitized subjects had peak IgE ab and LT responses against the allergenic fractions of the extract, while negative responses were obtained in the non-atopic controls. Only hyposensitized subjects had developed high IgG ab responses to the allergenic fractions. Most of the treated and untreated subjects showed IgG ab and LT responses to the high molecular weight fractions with low allergenic activity. Significantly higher IgE ab responses to these fractions were observed in the treated subjects than in the untreated ones, indicating potentiation of IgE ab responses against some antigens during immunotherapy. Some of the allergic subjects also responded to the fractions of low molecular size (mol. wt. 2000-5000) with low allergenic activity. Both IgE ab, IgG ab and LT responses to these fractions were observed.