Human Secretory Immunoglobulins

Abstract

A serum component with disulfide-linked secretory piece (SP) was detected. It was comparable to native secretory IgA in size and immunoelectrophoretic mobility, and also because its quaternary structure was highly stabilized, thus rendering an antigenic determinant of the bound SP inaccessible. Pools of normal human sera did not contain detectable amounts of this component; but single radial immunodiffusion revealed 59% positive sera in a control group (average concentration: 3.4 mg/100 ml), and 78% positive sera in an A-myeloma group (average concentration: 10.0 mg/100 ml). It was concluded that any condition that increases the permeability of glandular and mucosal tissues may raise the “spill-over” or absorption of secretory IgA into the circulation.