II. Definitions

  1. Antigen
    1. Molecules recognized by antibodies, or by T Cells (as peptides presented via MHC complex on host cells)
    2. Possible Antigens include proteins, nucleic acids, lipids, complex carbohydrates
    3. Antigens must be macromolecules, large enough to generate an immune response (Immunogens)
    4. Antigens have one or more Epitopes to which immune agents (e.g. antibodies) bind
  2. Hapten
    1. Antigen that is too small on its own to generate an immune response
    2. When Haptens are attached to macromolecules (immunogens), that may act as Epitopes for immune binding
  3. Immunogen
    1. Antigen that is large enough to generate an immune response
  4. Epitopes (Determinants)
    1. Antigen regions to which immune agents (e.g. antibodies) bind
  5. Antigen Processing
    1. Conversion to peptides of exogenous Antigens (endocytic path) and endogenous Antigens (cytosolic path)
    2. Peptide form is required for T-Cell recognition

III. Images

IV. Type: Cytosolic Pathway for Endogenous Antigens (MHC Class I Complex)

  1. Indications
    1. Endogenous Antigens (e.g. Intracellular Bacteria, intracellular Parasites, viruses)
    2. Antigen Processing starts within the cell cytosol
  2. Pathway
    1. Intracellular Antigens within the cell cytosol are processed by proteolytic enzymes within proteasome
      1. Processing results in converting Antigens to peptides
    2. Peptides are moved to endoplasmic reticulum where they are bound to MHC Class I molecules
    3. Antigen Peptide-MHC Class I Complex is moved to cell surface via golgi complex
  3. Antigen Presenting Cells (APC or Host Cells) displaying MHC Class I Complex
    1. All nucleated host cells (unlike MHC Class II of the Endocytic Pathway)
  4. Cells with Receptors Recognizing MHC Class I Complex
    1. CD8+ T-Cells (Cytotoxic T-Cells)

V. Type: Endocytic Pathway for Exogenous Antigens (MHC Class II Complex)

  1. Indications
    1. Exogenous Antigens
  2. Pathway
    1. Exogenous Antigens are engulfed by cells via Phagocytosis (endocytosis) as Phagosomes (endosomes)
      1. Cell membrane invaginates around the Antigens, surrounding them in a Vesicle
    2. Phagosomes fuse with Lysosomes (forming phagolysosomes)
      1. Proteolytic enzymes within the Lysosome breakdown or process the Antigen into peptides
    3. Antigenic peptides are bound to MHC Class IIMolecules while still inside the phagolysosome
    4. Antigen Peptide-MHC Class II Complex is moved to cell surface via secretory Vesicles
  3. Antigen Presenting Cells (APC or Host Cells) displaying MHC Class II Complex
    1. Langerhans Cells and Dendritic Cells
    2. Macrophages
    3. B-Cell (B-Lymphocyte)
  4. Cells with Receptors Recognizing MHC Class II Complex
    1. CD4+ T-Cells (T-Helper Cells)
      1. BCellActivation.jpg

VI. References

  1. Mahmoudi (2014) Immunology Made Ridiculously Simple, MedMaster, Miami, FL
  2. Guyton and Hall (2006) Medical Physiology, p. 419-50

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Related Studies

Ontology: Antigen-Presenting Cells (C0003315)

Definition (MSHCZE) Heterogenní skupina imunokompetentních buněk, která zprostředkovává buněčnou imunitní odpověď organismu zpracováváním a předkládáním antigenů T-buňkám. Tradiční buňky předkládající antigen zahrnují MAKROFÁGY, DENDRITICKÉ BUŇKY, LANGERHANSOVY BUŇKY a B-LYMFOCYTY. DENDRITICKÉ BUŇKY FOLIKULÁRNÍ nejsou tradičními buňkami předkládajícími antigen, ale mají na svém povrchu antigen ve formě imunokomplexu (ANTIGEN-PROTILÁTKA KOMPLEX) tak, aby byl rozpoznán B- buňkami, a proto jsou některými autory považovány za tento typ buněk.
Definition (NCI_NCI-GLOSS) A type of immune cell that boosts immune responses by showing antigens on its surface to other cells of the immune system. An antigen-presenting cell is a type of phagocyte.
Definition (NCI) A cell that enables a T-lymphocyte to recognize an antigen by engulfing the antigen, breaking down the antigen into smaller fragments which bind to MHC molecules on the surface of the antigen presenting cell. The T-lymphocyte can now recognize and bind with the MHC-linked antigen.
Definition (CSP) heterogeneous group of immunocompetent cells that mediates the cellular immune response by processing and presenting antigens to the T-cell receptor; traditional antigen presenting cells include macrophages, dendritic cells, Langerhans cells, and B-lymphocytes; follicular dendritic cells are also considered to be antigen presenting cells by some.
Definition (MSH) A heterogeneous group of immunocompetent cells that mediate the cellular immune response by processing and presenting antigens to the T-cells. Traditional antigen-presenting cells include MACROPHAGES; DENDRITIC CELLS; LANGERHANS CELLS; and B-LYMPHOCYTES. FOLLICULAR DENDRITIC CELLS are not traditional antigen-presenting cells, but because they hold antigen on their cell surface in the form of IMMUNE COMPLEXES for B-cell recognition they are considered so by some authors.
Concepts Cell (T025)
MSH D000938
English Accessory Cell, Immunologic, Accessory Cells, Immunologic, antigen presenting cell, Antigen-Presenting Cell, Antigen-Presenting Cells, Cell, Antigen-Presenting, Cell, Immunologic Accessory, Cells, Antigen-Presenting, Cells, Immunologic Accessory, Immunologic Accessory Cell, Immunologic Accessory Cells, ACCESSORY CELL IMMUNOL, CELL IMMUNOL ACCESSORY, ACCESSORY CELLS IMMUNOL, IMMUNOL ACCESSORY CELL, CELLS IMMUNOL ACCESSORY, IMMUNOL ACCESSORY CELLS, accessory cell, Antigen Processing Cell, antigen-presenting cell (APC), apc, antigen presenting cells, antigen-presenting cells, Dendritic cell, Antigen-presenting cell, Antigen-presenting dendritic cell, Antigen presenting cell, Antigen presenting cells, APC, antigen-presenting cell, Antigen Presenting Cells, Accessory Cell, Antigen Presenting Cell
French Cellules accessoires (immunité), Cellules présentatrices d'Ag, CPA (Cellule Présentatrice d'Antigène), Cellules présentatrices de l'antigène, Cellules présentatrices d'antigènes, Cellules accessoires immunitaires, Cellules présentatrices d'antigène, Cellules de présentation des antigènes, Cellule présentatrice d'antigène
Swedish Antigenpresenterande celler
Czech buňky předkládající antigen, buňky prezentující antigen
Finnish Antigeenia esittelevät solut
Italian Cellula accessoria immunologica, Cellule accessorie immunologiche, Cellule presentanti l'antigene
Russian ANTIGEN-PREZENTIRUIUSHCHIE KLETKI, ANTIGEN-PREDSTAVLIAIUSHCHIE KLETKI, DOBAVOCHNYE KLETKI IMMUNOLOGICHESKIE, АНТИГЕН-ПРЕДСТАВЛЯЮЩИЕ КЛЕТКИ, АНТИГЕН-ПРЕЗЕНТИРУЮЩИЕ КЛЕТКИ, ДОБАВОЧНЫЕ КЛЕТКИ ИММУНОЛОГИЧЕСКИЕ
Japanese 抗原提示細胞, 免疫付属細胞, 抗原付与細胞, 免疫提示細胞, 提示細胞-免疫
Croatian STANICE KOJE PREDOČUJU ANTIGEN
Polish Komórki prezentujące antygen
Norwegian Immunceller, aksessoriske, Antigenpresenterende celler, Aksessoriske immunceller
German Akzessorische Zellen, immunologisch, Immunologisch-akzessorische Zellen, Zelle, immunologisch-akzessorische, Antigenpräsentierende Zellen, Zellen, immunologisch-akzessorische
Dutch Antigenpresenterende cel, Antigenpresenterende cellen, Cel, antigenpresenterende, Helpercel, Helpercellen, Helpercellen, immunologische, Immunologische helpercellen
Portuguese Células Apresentadoras de Antígenos, Células Imunológicas Acessórias
Spanish Células Inmunológicas Accesorias, Células Presentadoras de Antígenos

Ontology: Epitopes (C0003316)

Definition (NCI) The simplest form of an antigenic determinant, on a complex antigenic molecule, which can combine with antibody or T cell receptor.
Definition (MSH) Sites on an antigen that interact with specific antibodies.
Concepts Immunologic Factor (T129)
MSH D000939
SnomedCT 52078008
English Antigenic Determinants, Determinants, Antigenic, Epitopes, antigenic determinant, Epitopes [Chemical/Ingredient], epitopes, epitope, Antigenic determinants, Antigenic determinant, Epitope, Epitope (substance), Binding Determinants, Antigenic Determinant
Swedish Epitoper
Czech epitopy, antigenní determinanty
Finnish Epitoopit
Italian Determinanti antigenici, Epitopi
Russian DETERMINANTY ANTIGENNYE, ANTIGENNAIA SPETSIFICHNOST', EPITOPY, ANTIGENNYE DETERMINANTY, АНТИГЕННАЯ СПЕЦИФИЧНОСТЬ, АНТИГЕННЫЕ ДЕТЕРМИНАНТЫ, ДЕТЕРМИНАНТЫ АНТИГЕННЫЕ, ЭПИТОПЫ
Japanese 抗原決定基, 抗原決定群, 抗原性決定群, 抗原特異性, エピトープ
French Déterminants antigéniques, Épitopes, Sites antigéniques
Croatian Not Translated[Epitopes]
Polish Determinanty antygenowe, Epitopy
Spanish Epítopos, Epítopes, determinante antigénico, epítope (sustancia), epítope, Determinantes Antigénicos
German Antigene Determinanten, Epitope
Portuguese Determinantes Antigênicos, Epitopos

Ontology: Antigens (C0003320)

Definition (NCI) Any substance, generally a protein, that stimulates the immune system and elicits an immune response. Recognition by the immune system elicits either a T-lymphocyte response, recognizing processed antigens, or a B-lymphocyte response, producing antibodies that bind to unprocessed antigens.
Definition (NCI_NCI-GLOSS) Any substance that causes the body to make a specific immune response.
Definition (MSH) Substances that are recognized by the immune system and induce an immune reaction.
Definition (PSY) Substances such as microorganisms or foreign tissues, cells, proteins, toxoids, or exotoxins having the ability to induce antibody formation.
Definition (CSP) any substance recognized by the immune system and inducing an immune reaction.
Concepts Immunologic Factor (T129)
MSH D000941
SnomedCT 7120007
LNC LP20739-6, LP20666-1, LP36615-0, LP30821-0
English Antigen, Antigens, immunogen, Antigens [Chemical/Ingredient], Ag, antigens, antigen, immunogens, ag, Immunogen, Antigen (substance), Antigen, NOS, Immunogen, NOS, Immunogens
Swedish Antigener
Czech antigeny
Finnish Antigeenit
Russian ANTIGENY, АНТИГЕНЫ
Japanese 抗原
French Antigène, Antigènes
Croatian ANTIGENI
Polish Antygeny
Norwegian Not Translated[Antigens]
Spanish antígeno (sustancia), antígeno, Antígenos
German Antigene
Italian Antigeni
Portuguese Antígenos

Ontology: Haptens (C0018593)

Definition (NCI) A substance that can act as an epitope for an antibody but that lacks immunogenicity unless coupled to a larger carrier molecule.
Definition (MSH) Small antigenic determinants capable of eliciting an immune response only when coupled to a carrier. Haptens bind to antibodies but by themselves cannot elicit an antibody response.
Definition (CSP) substances which can act as an epitope for antibody but lack immunogenicity unless coupled to a larger carrier molecule.
Concepts Immunologic Factor (T129)
MSH D006241
SnomedCT 112124006
English Haptens, incomplete antigen, partial antigen, haptin, proantigens, Haptens [Chemical/Ingredient], haptene, haptens, hapten, Hapten, Haptene, Haptin, Incomplete antigen, Partial antigen, Proantigen, Hapten (substance)
Swedish Haptener
Czech hapteny
Finnish Hapteenit
Russian GAPTENY, ГАПТЕНЫ
Japanese ハプテン, ハプテン部分抗原, 不完全抗原
French Haptènes
Croatian Not Translated[Haptens]
Polish Hapteny
Spanish antígeno incompleto, antígeno parcial, hapteno (sustancia), hapteno, proantígeno, Haptenos
German Haptene
Italian Apteni
Portuguese Haptenos

Ontology: Antigen Processing (C0206430)

Definition (NCI) The process by which foreign molecules are taken up by antigen presenting cells, proteolytically cleaved, and displayed on the cell surface in complex with MHC molecules.
Concepts Cell Function (T043)
MSH D017951
SnomedCT 40187000
English Antigen Processings, Antigen Processing, Antigen processing, function, Antigen processing, Antigen processing, function (observable entity), Antigen processing (function)
Czech antigen - zpracovávání
Portuguese Antígeno Processado
Spanish Proceso de Anticuerpo, procesamiento antigénico (entidad observable), procesamiento antigénico (función), procesamiento antigénico, procesamiento de un antígeno
German Antigenprozessierung
French Apprêtement antigénique, Apprêtement des antigènes, Apprêtement de l'antigène, Apprêtement d'antigène
Italian Processamento dell'antigene
Norwegian Antigenprosessering

Ontology: Antigen Presentation (C0206431)

Definition (GO) The process in which an antigen-presenting cell expresses antigen (peptide or lipid) on its cell surface in association with an MHC protein complex. [GO_REF:0000022, GOC:add, GOC:mtg_15nov05, ISBN:0781735149, PMID:15771591, PMID:15928678]
Definition (NCI) The event of providing fragments of foreign proteins, including viruses and bacteria, to the helper T cells. The presentation occurs through the display of the fragments of foreign proteins on the surface of the antigen-presenting cells (APC).(HIV Glossary; http://aidsinfo.nih.gov)
Definition (MSH) The process by which antigen is presented to lymphocytes in a form they can recognize. This is performed by antigen presenting cells (APCs). Some antigens require processing before they can be recognized. Antigen processing consists of ingestion and partial digestion of the antigen by the APC, followed by presentation of fragments on the cell surface. (From Rosen et al., Dictionary of Immunology, 1989)
Definition (CSP) process by which an antigen is presented to lymphocytes in a form they can recognize; antigen presenting cells may ingest or digest the antigen and present the fragments to the cell surface for recognition by the lymphocytes.
Concepts Cell Function (T043)
MSH D017951
English Antigen Presentations, antigen processing and presentation, antigen processing, Antigen Presentation, antigen presentation
Swedish Antigenpresentation
Czech antigen - nabízení
Finnish Antigeenin esittely
French Présentation antigénique, Présentation des antigènes, Présentation de l'antigène, Présentation d'antigène
Russian ANTIGENOV PREZENTATSIIA, ANTIGENOV OBRABOTKA, ANTIGENOV PREDSTAVLENIE, АНТИГЕНОВ ОБРАБОТКА, АНТИГЕНОВ ПРЕДСТАВЛЕНИЕ, АНТИГЕНОВ ПРЕЗЕНТАЦИЯ
Polish Prezentacja antygenu
Norwegian Antigenpresentasjon, Antigenframvisning
German Antigenpräsentation
Italian Presentazione antigenica
Dutch Antigeenpresentatie, Presentatie, antigeen-
Portuguese Apresentação do Antígeno
Spanish Presentación de Antígeno

Ontology: antigen processing and presentation of endogenous antigen (C1154990)

Definition (GO) The process in which an antigen-presenting cell expresses antigen (peptide or lipid) of endogenous origin on its cell surface in association with an MHC protein complex. [GOC:add, ISBN:0781735149, PMID:15771591, PMID:15928678]
Concepts Cell Function (T043)
English antigen presentation, endogenous antigen, antigen processing and presentation of endogenous antigen

Ontology: antigen processing and presentation of exogenous antigen (C1154993)

Definition (GO) The process in which an antigen-presenting cell expresses antigen (peptide or lipid) of exogenous origin on its cell surface in association with an MHC protein complex. [GOC:add, ISBN:0781735149, PMID:15771591, PMID:15928678]
Concepts Cell Function (T043)
English antigen presentation, exogenous antigen, antigen processing and presentation of exogenous antigen

Ontology: antigen processing and presentation of peptide antigen (C1154997)

Definition (GO) The process in which an antigen-presenting cell expresses peptide antigen in association with an MHC protein complex on its cell surface, including proteolysis and transport steps for the peptide antigen both prior to and following assembly with the MHC protein complex. The peptide antigen is typically, but not always, processed from an endogenous or exogenous protein. [GOC:add, ISBN:0781735149, PMID:15771591]
Concepts Cell Function (T043)
English antigen presentation, peptide antigen, peptide antigen processing and presentation, antigen processing and presentation of peptide antigen