Abstract

Antigens are fundamental components in the functioning of the immune system, serving as molecular signals that trigger immune responses. These substances, typically derived from pathogens such as bacteria, viruses, or other foreign entities, are recognized by immune cells through highly specific receptors. This article explores the structural and functional characteristics of antigens, including their classification into self and non-self-types, and their interaction with immune components such as B cells, T cells, and antigen-presenting cells. The role of epitopes, antigen presentation via the major histocompatibility complex (MHC), and the distinction between immunogenic and non-immunogenic antigens are discussed in detail. Understanding the mechanisms by which antigens stimulate both innate and adaptive immunity is essential for advancements in immunodiagnostics, vaccine development, and immunotherapy. This review provides a foundational overview for students and researchers seeking to grasp the critical role of antigens in initiating and shaping immune responses.