These studies pertain to the significance and mechanism of concordant fluctuation in sensitivity of peripheral leucocytes to release of histamine by unrelated allergens.
One type of concordant fluctuation occurs during injection of allergen. In this type, reduction of leucocyte sensitivity is only partial and recovery is rapid when injection of allergen ceases, and the reduction is related to degranulation of basophils and decrease in the histamine content. The nonspecific nature of the concordant, proportionate reduction in sensitivity to unrelated allergens suggests degranulation of a population of basophils in the circulation that apparently carries the reaginic antibodies for all allergens to which the subject is hypersensitive.
Another type of concordant loss of peripheral leucocyte sensitivity to unrelated allergens occurs uncommonly, without clear relation to allergen injection. In this type, reduction of leucocyte sensitivity proceeds gradually to the point of unresponsiveness to allergen and persists for prolonged periods. The nonspecific nature of this type is not associated with decrease in histamine content of the peripheral leucocytes (basophils).
In both types, simultaneous determination of other indices of hypersensitivity (sensitivity of skin and bronchi, and reaginic antibody content of serum) showed no significant changes concomitant with fluctuation in peripheral leucocyte sensitivity. This suggests basophils in the peripheral blood behave differently from mast cells in tissues.
The findings point to important limitations in the use of in-vitro measurement of sensitivity of peripheral leucocytes (basophils) as an index of hypersensitivity of a person and as a means of monitoring the efficacy of injection therapy. The term ‘desensitization’ should be used precisely to distinguish loss of hypersensitivity of tissues throughout the body from reduced sensitivity of only certain cells.