Histamine-releasing activity in supernatants of mononuclear cells: Contribution of monocyte chemotactic protein-1 activity compared with IgE- dependent activity

Background: Supernatants of cultured human mononuclear cells contain factors that induce histamine release from basophils. Some of the histamine- releasing factors present are IgE-independent, but an IgE-dependent form has also been described. The IgE that does respond to the IgE-dependent histamine-releasing factor was defined as IgE⁺. Objective: This study was conducted to analyze the contribution of chemokines, such as monocyte chemotactic protein-1 (IgE-independent), to improve the detection of IgE- dependent histamine-releasing factor. Methods: Supernatants were prepared from mononuclear cells of three subjects. Monocyte chemotactic protein-1 content and histamine-releasing activity (HRA) were measured. Depletion of chemokine activity was carried out with heparin-Sepharose (Pharmacia, Uppsala, Sweden). Results: Replacing IgE⁺ on basophils with IgE⁺ serum decreased the correlation between monocyte chemotactic protein-1 and histamine release (p = 0.80, n = 280 vs p = 0.12, n = 18; p for difference between p values: <0.05). After depletion of chemokines in three supernatants derived from mononuclear cells, IgE-dependent HRA was still present. Conclusion: We conclude that in supernatants derived from mononuclear cells, the IgE-independent HRA masks the IgE-dependent HRA. The latter can be more clearly detected after depletion of chemokine activity with heparin- Sepharose.