Increased numbers of circulating basophil progenitors in atopic patients.

Recruitment of basophils to sites of homocytotropic antibody-mediated hypersensitivity reactions has been well documented in both experimental and clinical situations. Mechanisms underlying tissue basophil accumulation, however, remain unclear and may involve chemotaxis, cell proliferation, or both. We have recently reported the presence in human blood of circulating basophil/mast cell progenitors on the basis of histamine content of granulocyte colonies grown in methylcellulose. In the current studies we have analyzed the peripheral blood of 30 patients with atopy and 25 comparable control subjects for frequency of basophil/mast cell progenitors by analysis of the histamine content of individual granulocyte colonies. Forty percent of granulocyte colonies in cultures of atopic patients contained histamine in comparison to only 11% in cultures of control subjects (p less than 0.001). Histamine content per colony as well as mean histamine per cell in each colony was higher in granulocyte colonies of atopic subjects and could not be related to colony size or culture conditions. Granulocyte colony growth was enhanced by antigen-stimulated, peripheral blood lymphomononuclear cell--conditioned media of atopic patients. Histamine-positive colonies were found more frequently in active versus quiescent atopic disease (p less than 0.05). These results are consistent with the hypothesis that basophils accumulate at sites of allergic reactions at least in part by recruitment of progenitors from circulation and subsequent differentiation in situ in response to lymphokines. Further studies by use of hemopoietic assays could elucidate the contribution of basophil production to the development of allergic conditions.