Histamine release from human leucocytes by IgG4 subclass in the sera of allergic children.

Our studies on histamine release from normal washed leucocytes sensitised with sera of children allergic to various inhaled and ingested allergens show that besides IgE, IgG4 present in these sera was capable of sensitising leucocytes of normal donors, and these leucocytes released histamine on challenge with anti-IgG4. By contrast, antisera of other subclasses of IgG released very small amounts of histamine from sensitised leucocytes. A discordant correlation between skin tests and RAST IgE was observed in some children. Significantly greater amounts of histamine were released from normal leucocytes sensitised with serum from these children when challenged with anti-IgG4 compared to anti-IgE. These studies indicate that IgG4 merits further study as a reaginic marker in atopic diseases of the children with possible prognostic significance.