A 3 year old child presents with a history of repeated sinopulmonary infections caused by encapsulated organisms. Which of the following is most likely to be deficient in this case?: (A) IgG4, (B) IgG3, (C) IgG2, (D) IgG1
Answer is C. Deficiency of IgG2 results in recurrent sinopulmonary infections with encapsulated organisms. Deficiency of IgG1 - Bacterial infections (Diptheria, tetanus) Deficiency of IgG3 - Viral infections Deficiency of IgG4 - Parasitic infections IgG is the only maternal immunoglobulin that is normally transpoed across the placenta and provides natural passive immunity to the newborn. Maximum placental transfer - IgG1 Minimum placental transfer - IgG2 Reference: Ananthanarayan and Paniker&;s Textbook of Microbiology Tenth edition