Video Transcript
In the cell-mediated immune
response, what is the primary role of the major histocompatibility complex, MHC? (A) To bind to the antigen
presented on the surface of a macrophage and initiate the immune response. (B) To stimulate phagocytes to
carry out phagocytosis. (C) To break down the pathogen once
it has been engulfed by a macrophage. Or (D) to present the antigens of
digested pathogens on the cell surface of macrophages.
Macrophages are specialized white
blood cells which are capable of carrying out phagocytosis and presenting antigens
to T cells. During the cell-mediated immune
response, a macrophage will engulf an extracellular pathogen, such as a
bacterium. Inside the macrophage, the
bacterium will then be digested and processed using enzymes. The fragments of the digested
pathogen are the antigens which will be presented by the macrophage. Inside the macrophage, a major
histocompatibility complex, or MHC, is assembled around an antigen. And together they are transported
to the cell surface membrane. This is how antigens are presented
to T cells of the specific immune response.
We have therefore determined that
the correct answer is (D). The primary role of the MHC is to
present the antigens of digested pathogens on the cell surface of macrophages.
