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The secret mission of antigen-presenting cells: How do they influence T cell priming?
The operation of the immune system is quite complex, among which cellular immunity plays a particularly critical role. Cellular immunity, that is, cell-mediated immune response, does not rely on the production of antibodies, but instead fights antigens by activating phagocytes, specific cytotoxic T lymphocytes and releasing a variety of cytokines. This is not only the primary line of defense against foreign pathogens, but also plays an important role in the prevention and treatment of various chronic diseases and tumors.
In the late 19th century, according to the traditional medical system of Hippocrates, the immune system was originally divided into two branches: fluid immunity and cellular immunity. The protective function of fluid immunity depends on body fluids, while cellular immunity is closely related to cells. CD4 cells or helper T cells are able to provide protection against different pathogens, while immature T cells transform into activated effector T cells after contact with antigen presenting cells (APCs).
Antigen presenting cells, such as macrophages, dendritic cells, and some B cells, load antigenic peptides on their surface and display them to T cells through the major histocompatibility complex (MHC). body.
Of these APCs, dendritic cells are considered the most specialized because they are almost exclusively focused on uptake and presentation of antigens. Activated effector T cells can be divided into three main categories: cytotoxic T cells, TH1 cells, and TH2 cells, each of which corresponds to different types of pathogens and plays different roles.
Cell-mediated immunity is directed not only against microorganisms that survive within phagocytes, but also against pathogens that infect non-phagocytes. This immune response is particularly effective in removing virus-infected cells, but it also plays an important role in fighting fungi, protozoa, cancer cells, and intracellular bacteria.
This immune system response targets each pathogen individually, ultimately leading to cell death and thus preventing the spread of the pathogen.
In the development of cellular immunity, all cell types originate from common lymphoid precursors. These cells then differentiate into different cell types to carry out their respective immune tasks. CD4+ T cells are mainly divided into two categories: TH1 and TH2, while CD8+ cytotoxic T cells are divided into TC1 and TC2.
So how does signaling between these cells affect the overall immune response? Taking TH1 cells as an example, they mainly secrete interferon γ, which can activate macrophages and enhance their ability to phagocytize and kill pathogens. This process not only occurs in healthy immune responses, but can also cause problems in autoimmune diseases or chronic inflammation.
Interferon gamma works in conjunction with tumor necrosis factor (TNF) to effectively fight internal pathogens, such as intracellular bacteria and viruses.
As research progressed, scientists in the United States and other regions discovered various subtypes of T cells and confirmed their multiple roles in immunity. Most importantly, the current studies highlight the important role of antigen-presenting cells in initiating and regulating these T cell functions.
Clinically, this knowledge could be used to improve vaccine effectiveness or develop new therapies, particularly against cancer and autoimmune diseases. In this ever-changing field of medicine, researchers are exploring how to harness these cellular interactions to improve patient health.
However, how many hidden tasks and potential medical opportunities can we uncover in the process of understanding these complex immune mechanisms?
