Characteristics of histamine-releasing activity in the sera of patients with chronic idiopathic urticaria.

BACKGROUND

The serum histamine-releasing activity (HRA) found in a sizable percentage of patients with chronic idiopathic urticaria (CIU) has been partially characterized. However, the variable effect of individual HRA+ sera in basophils of different donors and the relationship of HRA to the clinical course require further investigation.

OBJECTIVE

The study was performed to characterize the HRA found in sera of some members of a sizable group of carefully evaluated patients with CIU.

METHODS

Sera of 70 patients with CIU, evaluated with a standard protocol, were screened for increased HRA. HRA+ sera were fractionated, heated, and tested on unaltered and altered basophils obtained from a panel of normal donors. HRA levels were compared with concomitant clinical manifestations.

RESULTS

HRA+ sera were found in 30% of our patients with CIU, HRA was predominantly in the IgG fraction, sensitive to 56 degrees C heating for 4 hours, and generally reacted more with IgE-stripped basophils. Considerable variation in the degree of response to HRA+ sera in the basophils of different normal subjects did not correlate with the degree of response of these cells to heterologous anti-IgE antiserum. Serum HRA levels were generally much lower when symptoms decreased in these patients with CIU.

CONCLUSION

Serum HRA from patients with CIU appears to bind most commonly to the IgE receptor and may be a marker of clinical disease activity. HRA appears in an IgG-containing fraction of the serum and may contain IgE in some cases.