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
  2. 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. 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)

IV. 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. 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)

V. References

  1. Mahmoudi (2014) Immunology Made Ridiculously Simple, MedMaster, Miami, FL

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Related Studies

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: 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