Human secretory immunoglobulins. II. Salivary secretions from individuals with selectively excessive or defective synthesis of serum immunoglobulins.
Increased amounts of IgG were transmitted into the salivary secretions of patients with elevated serum levels of this immunoglobulin. Both its glandular and extra-glandular transfer apparently depended upon passive diffusion or epithelial `leakage'. 
 
High serum levels of IgM (in macroglobulinaemia), and especially local synthesis of this immunoglobulin (in IgA deficiency), enhanced its transfer into the saliva. The transmission through secretory epithelium (glandular transfer) seemed to be an active or selective process, probably dependent upon specific `transfer sites' in the heavy polypetide chains of IgM. 
 
The transmitted immunoglobulin (secretory IgM) was physicochemically and immunochemically similar to its 19S counterpart in serum. In IgA-deficient secretions no significant association between immunoglobulin components and secretory piece (SP) could be detected; the latter was physicochemically and immunochemically characterized as free SP.