Describe three distinct mechanisms by which antibodies eradicate infection

Question

What will be an ideal response?

Answer 1

(i) Neutralization. By binding to the surface of a pathogen, antibodies interfere with the ability of the pathogen to grow and replicate. Antibody binding to a pathogen or a bacterial toxin can also inhibit its binding to receptors on host cells and therefore prevent its entry into cells. (ii) Opsonization. Antibody coating the surface of a pathogen or toxin can promote phagocytosis of the antibody-covered particle. Antibodies acting in this way are known as opsonins. The antibody-bound material interacts with Fc receptors on the surface of phagocytic cells such as macrophages and neutrophils, which bind the constant region (the stem) of the antibody. Stimulation of Fc receptors in this way stimulates the engulfment and degradation of antibody-coated material by the phagocyte. (iii) Complement activation. IgG or IgM antibody bound to a pathogen stimulates activation of the complement system, leading to the deposition of complement proteins on the surface of the pathogen. Certain of these act as opsonins and bind to complement receptors on phagocytic cells to stimulate the phagocytosis and destruction of the pathogen.