The endolymphatic sac acts as the afferent limb of inner ear immunity since it can concentrate and primarily synthesize antibody. IgG is the most common antibody produced with IgM, IgA, and secretory component being present in lower concentrations. The distal endolymphatic sac is the site of immunologic activity due to extensive perisaccular lymphatics. Antibody production is independent of serum or cerebrospinal fluid levels. Secondary exposure to antigen in the inner ear induces a more intense response than primary exposure to antigen.
Autoimmunity occurs with loss of homeostatic control in the immune system.
Host tissues become recognized as foreign and induce damaging vasculitis and fibrosis. Veldman described a continuum of autoimmunity. Patients with idiopathic autoimmune sensorineural hearing loss present most commonly with bilateral progressive hearing loss. Fifty percent have vestibular signs, and symptomatically progress over weeks to months. Twenty percent of Hughes' study later manifested signs of systemic autoimmune disease.