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Presentation of exogenous antigens Exogenous antigens: macrophages and dendritic cells bind antigens using a number of different receptors for PAMPs, complement fragments, or antibodies. Opsonized bacteria and antigens are ingested by a process called phagocytosis. The mechanism for class II molecule delivery differs with macrophages and B cells. B cells use receptor-mediated endocytosis to ingest … Read more

Introduction to antigen-presenting cells Antigen-Presenting Cells (APCs) are a heterogeneous group of immune cells that mediate the cellular immune response by processing and presenting antigens for recognition by certain lymphocytes such as T cells. Large-molecular-weight proteins must be reduced to a length of 8 to 30 amino acids before being loaded with antigens into class I and … Read more

Introduction to Antigen-Presenting Molecules The immune system defends the host against microbial infections and mutant cells. In defense of the host, the immune system must differentiate between foreign proteins and “self-proteins.” Surface display proteins are used as markers of “self.” Early animal skin transplantation studies demonstrated that rejection or acceptance of grafts was dependent on … Read more

Hapten Haptens are small-molecular-weight compounds that evoke an immune response only when they are attached to carrier proteins. In vivo, haptens readily bind to serum proteins such as albumin. The combined molecular weights of albumin and the hapten need to exceed 3000 MW to stimulate the immune system. The immune response is directed at both … Read more

Exogenous Antigens Exogenous antigens enter the body via the oral, respiratory, and parenteral routes. In general, exogenous antigen are immunogenic structures expressed on extracellular bacteria, fungi, viruses, and pollens. Exogenous antigens are ingested by macrophages, and epitopes are presented in the context of class II molecules to Th2 cells. In some cases, exogenous antigens may … Read more

Antigen The antigen is a chemical that can activate lymphocytes, the body’s infection-fighting white blood cells, and stimulate an immunological response. Antigens are divided into two categories: foreign antigens (or heteroantigens) and autoantigens (or self-antigens). Antigens that come from outside the body are called foreign antigens. Types of antigens White Blood Cell Alloantigens White blood … Read more

The concepts of immunogenicity and antigenicity are critical to the understanding of adaptive immunity. By definition, an immunogen is a molecule that stimulates the immune system to produce a response. An antigen is the part of the immunogen that reacts with immune effector cells or soluble antibodies. The term allergen is used to denote an … Read more