We describe the characteristics of in vitro histamine release from human basophils passively sensitized with serum from a penicillin-allergic individual. The histamine release is induced by a synthetic bivalent hapten, bis benzylpenicilloyl 1,6 diaminohexane (BPO)2. We present data on the effect of a monovalent hapten, benzylpenicilloyl formyl-l-lysine (BPO)1, on the histamine release. We also examine how histamine release depends on the concentration of serum used for passive sensitization, the source of cells used for passive sensitization, and the time allowed for histamine release.

We interpret these experiments in terms of a theory of equilibrium binding of bivalent haptens to cell surface antibody that is presented in the previous paper. The results are consistent with the idea that the amount of histamine release is controlled by the number of cross-linked IgE molecules on the cell surface. In particular, the histamine dose-response curve rises because cross-links rise, has a maximum because the cross-links are a maximum, and falls because the cross-links fall.

1

This work was performed in part under the auspices of the United States Department of Energy.

2

This work was supported by Grant AI07290 from the National Institute of Allergy and Infectious Diseases, The National Institutes of Health. Publication No. 309 of the O'Neill Research Laboratories at the Good Samaritan Hospital.

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