Question

Describe the role of antigen-presenting cells in the immune response

Answer 1

Antigen-presenting cells (APCs) are aheterogeneous group of immune cells that mediate the cellular immune response by processing and presenting antigens for recognition by lymphocytes such as Tcells. The APCs include dendritic cells, macrophages, Langerhans cells and B cells.

Antigen-presenting cells are involved in both the innate and adaptive immune responses.

Role of Antigen presenting cells in adaptive immunity

Antigen-presenting cells are vital for effective adaptive immune response, as the functioning of both cytotoxic and helper T cells are dependent on APCs. Antigen presentation allows for specificity of adaptive immunity and can contribute to immune responses against both intracellular and extracellular pathogens.

An antigen-presenting cell (APC)is an immune cell that detects, engulfs, and informs the adaptive immune response to an infection. When a pathogen is detected, these APCs will phagocytose the pathogen and digest it to form many different fragments of the antigen. Antigen fragments then transported to the surface of the APC, where they wserve as an indicator to other immune cells.

After phagocytosis by antigen presenting cells, the phagocytic vesicle fuses with an intracellular lysosome forming phagolysosome. Within the phagolysosome, the components are broken down into fragments; the fragments are then loaded onto MHC class I or MHC class II molecules and are transported to the cell surface of antigen presenting cells for antigen presentation.

T lymphocytes cannot properly respond to the antigen unless it is processed and embedded in an MHC II molecule. APCs express MHC on their surfaces, and when combined with a foreign antigen, these complexes signal a “non-self” invader. Once the fragment of antigen is embedded in the MHC II molecule, the immune cell are respond. Helper T- cells are one of the main lymphocytes that respond to the antigen-presenting cells.