Journal of Cell Science & Therapy
Open Access

Antigen Presentation in Cellular Immunology: Mechanisms and Applications

Amit Dustin^{* *}Correspondence: Amit Dustin, Department of Neurology, University of Oxford, Oxford, United Kingdom, Email:

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Description

Antigen presentation is a fundamental process in cellular immunology that plays a pivotal role in initiating and regulating immune responses. It involves the presentation of antigens, typically peptides derived from pathogens or other sources, to immune cells such as T lymphocytes.

Major Histocompatibility Complex (MHC)

The Major Histocompatibility Complex (MHC) molecules, also known as Human Leukocyte Antigens (HLAs) in humans, are central to antigen presentation. MHC molecules are glycoproteins found on the surface of almost all nucleated cells and are divided into two classes: MHC class I and MHC class II. Each class plays distinct roles in presenting antigens to different subsets of T cells.

MHC class I molecules primarily present antigens derived from intracellular pathogens, such as viruses and intracellular bacteria. These antigens are generated within the cytosol of the host cell and are processed into short peptide fragments by the proteasome. The peptides are then transported into the Endoplasmic Reticulum (ER), where they bind to newly synthesized MHC class I molecules. The peptide-MHC class I complex is then transported to the cell surface, where it can be recognized by CD8⁺ Cytotoxic T cells (CTLs). This interaction is essential for CTL activation and the elimination of infected or abnormal cells.

MHC class II molecules are primarily involved in presenting antigens derived from extracellular pathogens, such as bacteria and parasites, as well as antigens from engulfed particles and dead cells. These antigens are internalized by Antigen-Presenting Cells (APCs), such as dendritic cells, macrophages, and B cells, through phagocytosis or endocytosis. Within the APCs, the antigens are processed into peptides within endosomal compartments and then loaded onto MHC class II molecules. The peptide-MHC class II complex is then transported to the cell surface, where it can be recognized by CD4⁺ helper T cells.

This interaction is critical for activating helper T cells, which orchestrate and regulate immune responses by secreting cytokines and providing help to other immune cells.

Mechanism

The mechanisms of antigen presentation are not limited to infection scenarios they also play important roles in autoimmune diseases, transplant rejection, and cancer immunotherapy. In autoimmune diseases, such as rheumatoid arthritis and multiple sclerosis, self-antigens are mistakenly presented to T cells, leading to the activation of autoreactive T cells and the destruction of healthy tissues.

Cancer immunotherapy

Cancer immunotherapy helps in manipulating antigen presentation pathways is key to enhancing the recognition and elimination of cancer cells by the immune system. Strategies such as dendritic cell vaccines aim to exploit the ability of dendritic cells to present tumor antigens to T cells, thereby stimulating anti-tumor immune responses. Similarly, immune checkpoint inhibitors target pathways that regulate T cell activation, enhancing the ability of cytotoxic T cells to recognize and kill cancer cells presenting specific tumor antigens.

Conclusion

In antigen presentation is a dynamic and essential process in cellular immunology that underpins the initiation, regulation, and modulation of immune responses. The complex mechanisms by which antigens are processed and presented by MHC molecules dictate the specificity and effectiveness of immune responses against pathogens, tumors, and self-antigens. By elucidating these mechanisms researchers create an innovative approach to treat infectious diseases, autoimmune disorders, and cancer through targeted manipulation of antigen presentation pathways.