Pathology · patient case question
Which immunoglobulin predominates in saliva?
Patient case: The mouth that will not stay wet
demo: 54-year-old female
chief: Burning, sticky mouth for the past eight months; food gets caught and she wakes at night to sip water.
history: Hashimoto thyroiditis. Her rheumatologist ordered an autoantibody panel after she reported gritty, burning eyes.
meds: Levothyroxine 75 mcg daily. Amitriptyline 25 mcg at night for chronic tension headache.
findings: Anti-SSA (Ro) strongly positive. Salivary pooling is absent; the mucosa is dry and the tongue is fissured with papillary atrophy. Cracking and erythema at both commissures. Two new cervical lesions since her last visit a year ago.
Show answer and explanation
Correct answer: D. Secretory IgA
- A. IgG is the dominant immunoglobulin of serum and reaches the mouth mainly through gingival crevicular fluid rather than through saliva itself.
- B. IgM is the first antibody produced in a primary response and is largely intravascular because of its size.
- C. IgE mediates type I hypersensitivity and is present in only trace quantities.
- D. Correct. Secretory IgA is the dominant immunoglobulin of all mucosal secretions including saliva. It is a dimer joined by a J chain and wrapped in a secretory component that protects it from proteolysis in the oral environment.