The immune response in a healthy 12-year-old boy is observed after a recurrent bacterial infection. It is characterized by a rapid increase in pathogen-specific immunoglobulin levels. The immunoglobulins bound to the bacteria also attach to phagocytic cells (eg, macrophages, neutrophils) to enhance phagocytosis. Which of the following immunoglobulin regions is most likely involved in interacting with these phagocytic cells?

Question

The immune response in a healthy 12-year-old boy is observed after a recurrent bacterial infection.  It is characterized by a rapid increase in pathogen-specific immunoglobulin levels.  The immunoglobulins bound to the bacteria also attach to phagocytic cells (eg, macrophages, neutrophils) to enhance phagocytosis.  Which of the following immunoglobulin regions is most likely involved in interacting with these phagocytic cells?

Quizplus · Accepted Answer

Eductional Objective: Immunoglobulin contains a Fab fragment that binds to antigen and an Fc fragment that activates complement and/or interacts with immune cells.  The Fc fragment of IgG activates the classical complement cascade (constant heavy chain region 2) and serves as a ligand for the Fc receptor on phagocytes (constant heavy chain region 3).

The Immune Response in a Healthy 12-Year-Old Boy Is Observed