A 22-year-old man comes to the physician for a 2-day history of low-grade fever and non-productive cough. Physical examination shows pale conjunctivae. X-ray of the chest shows bilateral interstitial infiltrates. A sample of blood that is drawn for testing spontaneously agglutinates during transportation to the laboratory. An immunoglobulin with which of the following functions is most likely responsible for the agglutination?
Enhanced affinity
Enhanced avidity
Induction of mast cell degranulation
Secondary immune response induction
Secretion across mucosal surfaces
