The induction of IgA synthesis in normal peripheral blood lymphocytes cultured in the presence of 5 different B-cell activators was studied by immunofluorescence using monoclonal antibodies to the two subclasses. The surface phenotype of normal cells after overnight culture in the absence of mitogen showed a mean ratio IgA1:IgA2 of 2.7:1; cells with cytoplasmic IgA were very rare. Results obtained on different donors after stimulation showed considerable variation; IgA1 was the predominant subclass in Epstein-Barr virus-stimulated cultures, whereas pokeweed mitogen induced a predominantly IgA2 response; cells stimulated with Staphylococcus aureus, Branhamella catarrhalis and lipopolysaccharide and unstimulated cells showed a 1:1 ratio of the subclasses. It is concluded that in this system IgA subclass expression is a function of the activator employed.
Antigens, Surface B-Lymphocytes