Jason Chow, a 5-year old body was admitted to the National University Hospital: Immunology Assignment, NUS,, Singapore

Assignment Details:

Jason Chow, a 5-year old body was admitted to the National University Hospital due to severe sinus infection. Group A β-hemolytic streptococci were cultu
red from his nose and throat. His serum was tested for antibodies against streptolysin O, an antigen secreted by streptococci, but no antibodies against the antigen was detected.

His serum immunoglobulins were measured. The results showed that his serum IgG level was 5 mg/dL (normal 600-1500 mg/dL), IgA was undetectable (normal 75-150 mg/dL). Jason has red blood cells of group O. His serum anti-A antibody titer was 1:3000 and the anti-B antibody titer was 1:2000. Both anti-A and anti-B antibodies were of the IgM class only. He has a history of recurrent sinus infections since he was 1 year old.

Question 1: What disease does Jason have?

Question 2: Describe the immune mechanism underlying the development of this disease.