A Level Biology Practice Exam

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What is the function of an antigen-presenting cell (APC)?

Incorporates foreign DNA into its genome
Displays foreign antigens for recognition by other immune cells
Produces antibodies against pathogens
Filters harmful substances from the bloodstream

The correct answer is: Displays foreign antigens for recognition by other immune cells

The primary function of an antigen-presenting cell (APC) is to display foreign antigens for recognition by other immune cells, particularly T lymphocytes. APCs, which include dendritic cells, macrophages, and B cells, play a crucial role in the immune response by processing and presenting antigens derived from pathogens. When an APC encounters a pathogen, it engulfs and digests the pathogen, then presents peptide fragments of the pathogen on its surface bound to major histocompatibility complex (MHC) molecules. This antigen-MHC complex is essential for the activation of T cells. The T cells, upon recognizing the specific antigens presented, become activated and can initiate an immune response, leading to the destruction of the pathogen. This process is essential for adaptive immunity, where the body develops a tailored response to specific pathogens. The recognition of these antigens by T cells also aids in the formation of memory cells, which ensures a quicker and more effective response upon subsequent exposures to the same pathogen. In this way, the role of APCs is pivotal in bridging the innate and adaptive immune responses.