Question

Regulation of the immune response – the role of antibody molecules. Can the administration of antibody against a certain antigen (given passively to an individual) prevent that individual from producing an active immune response if subsequently injected with that antigen? If so how does that work? Does the suppressing antibody work by covering the antigenic sites, in effect hiding the antigen? Or might it more involve the destruction of the antigen? (Hint: what happened when only (Fab)2’ fragments were given?)

Answer 1

Q1<ANS>Passive immunity results when a person is given someone else’s antibodies, whereas active immunity results when a person’s immune system works to produce antibodies and activate other immune cells to certain pathogens.

Active immunity results when a person’s immune system works to produce antibodies and activate other immune cells to certain pathogens.person encounters that pathogen again, long-lasting immune cells specific to it will already be primed to fight it.

The protection offered by passive immunization is short-lived, usually lasting only a few weeks or months. But it helps protect right away.

. It has long been known that induction of immune responses to an antigen can be suppressed by passive transfer of antibody specific to the same antigen.The mechanism by which preexisting or passively transferred antibody suppresses the antibody response is not entirely clear. It could be either by covering the immuno- genic sites of the antigen and thereby preventing or diminishing the immunogenic stimulus, or by a direct suppressive action on the cells destined to respond to the antigen. In the broad sense, either of these actions might be considered a "feedback mechanism" since the product of the response, antibody, would serve, directly or in- directly, to prevent or diminish the response.  larger amounts of passive antibody are needed to suppress responses to the larger doses of antigen, it would appear that amounts of nonimmunogenic antigen proportional to the total antigen given may be retained

Q2<ANS>

F(ab')2fragment antibodies eliminate non-specific binding between Fc portions of antibodies and Fc receptors on cells (such as macrophages, dendritic cells, neutrophils, NK cells and B cells) and penetrate tissues more efficiently due to their smaller size. As fragment antibodies do not have Fc portions, they do not interfere with anti-Fc mediated antibody detection.