What do antibodies do
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The Multifaceted Role of Antibodies in Immune Defense
Antibodies, also known as immunoglobulins, are crucial components of the immune system, playing diverse roles in protecting the host from pathogens. Their functions extend beyond mere pathogen binding, encompassing a range of mechanisms that contribute to both innate and adaptive immunity.
Antibody Binding and Pathogen Neutralization
One of the primary functions of antibodies is to bind to antigens, which are specific molecules on the surface of pathogens. This binding can directly neutralize pathogens by preventing their entry into host cells or by blocking their toxic effects 12. The structural basis of this antigen recognition involves the complementarity determining regions (CDRs) of the antibody, which are highly variable and specific to each antigen .
Effector Functions and Immune System Activation
Beyond neutralization, antibodies activate various components of the immune system. They interact with effector cells and molecules such as complement proteins to enhance pathogen clearance. This interaction can lead to the formation of immune complexes that facilitate the uptake and destruction of pathogens by phagocytic cells 12. Additionally, antibodies can modulate immune responses by increasing antigen presentation and regulating inflammation .
Noncanonical Functions of Antibodies
Recent research has uncovered noncanonical functions of antibodies, which include activities typically associated with other proteins like cytokines and enzymes. These functions can involve untypical strategies for pathogen neutralization and immune regulation, expanding our understanding of the adaptive immune response .
Intracellular Antibody Functions
Traditionally, antibodies are known to function extracellularly. However, they also play roles inside cells. For instance, antibodies can be internalized and interact with intracellular receptors such as TRIM21, which helps in the degradation of pathogens within the cytosol . This intracellular activity represents a second line of immune defense, adding another layer to the antibody's protective functions.
Therapeutic Applications of Antibodies
Antibodies are not only vital for natural immune defense but also serve as powerful therapeutic agents. Monoclonal antibodies, in particular, are used in cancer immunotherapy to manipulate tumor-related signaling and promote antitumor immune responses . Their ability to specifically target and modulate immune components makes them versatile tools in clinical settings.
Maintenance and Regulation of Antibody Levels
The production and maintenance of antibodies are tightly regulated processes. B lymphocytes differentiate into plasma cells that secrete antibodies, contributing to both immediate and long-term immune responses. The survival and longevity of these plasma cells are crucial for maintaining stable serum antibody levels and ensuring lasting immunity .
Glycosylation and Antibody Function
The function of antibodies is also influenced by post-translational modifications such as glycosylation. Glycans, particularly sialic acid, attached to antibodies can significantly affect their effector functions. This glycosylation is an important regulator of antibody activity across different classes, including IgG, IgE, IgM, and IgA .
Conclusion
Antibodies are versatile and dynamic molecules that play multiple roles in immune defense. From direct pathogen neutralization to the activation of immune responses and therapeutic applications, their functions are integral to both innate and adaptive immunity. Understanding these diverse roles not only enhances our knowledge of immunology but also informs the development of vaccines and therapeutic antibodies.
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