Affinity of immunoglobulin for heterologous tissue mast cells. A study with the fluorescent antibody method.

A double layer immunofluorescence method was used to explore the affinity of immunoglobulins and immunoglobulin fragments for the mast cells of the mouse tongue. Human IgG but not IgA or IgM showed such an affinity as revealed by fluorescence of globulin attached to the mast cell surface and to the mast cell granules. This affinity was found also in isolated H(γ) chains but not in the light chains of IgG. After papain digestion, the Fab and Fc fragments obtained showed no affinity for mouse tongue mast cells though the 5S fragment obtained after pepsin digestion retained activity. The human immunoglobulin sub-class IgG lacks the ability to bind to mouse tongue mast cells. In guinea-pig serum, γ- but not γ-globulin showed an affinity for mouse tongue mast cells. It was suggested that a specific attachment site for mouse tongue mast cell surface receptors was present on the γ chain of human IgG and that this site was in a position susceptible to attck by papain hydrolysis.