The process by which antigens are broken down and presented by MHC molecules to immune cells.
Antigen processing: The mechanisms by which antigens are processed and presented to T cells for recognition and activation.
Major Histocompatibility Complex (MHC): A highly polymorphic genetic locus that encodes proteins responsible for antigen presentation.
MHC class I: A type of MHC molecule that is expressed on all nucleated cells and presents peptides to CD8+ T cells for recognition.
MHC class II: A type of MHC molecule that is expressed on antigen-presenting cells and presents peptides to CD4+ T cells for recognition.
Antigen-presenting cells (APCs): Cells that present antigens to T cells for recognition, including dendritic cells and macrophages.
T cell receptors (TCRs): Proteins expressed on the surface of T cells that recognize antigen peptide-MHC complexes.
Co-stimulation: Additional signals required for T cell activation beyond antigen recognition.
Cross-presentation: The process by which exogenous antigens are presented on MHC class I molecules.
Endogenous antigen processing: The process by which intracellular antigens are processed and presented on MHC class I molecules.
Exogenous antigen processing: The process by which extracellular antigens are processed and presented on MHC class II molecules.
Antigen presentation pathways: The different pathways by which antigens can be processed and presented, including the cytosolic pathway, the endocytic pathway, and the cross-presentation pathway.
Antigenic determinants: Specific regions of an antigen that are recognized by T cells.
Immunogenicity: The ability of an antigen to induce an immune response.
T cell activation: The process by which T cells are activated to carry out immune responses.
Immune tolerance: The process by which the immune system learns to distinguish self from non-self to avoid attacking healthy tissues.
Autoimmunity: The breakdown of immune tolerance resulting in the attack of healthy tissues by the immune system.
Immune evasion: Strategies used by pathogens to evade detection and clearance by the immune system.
Immune checkpoint molecules: Molecules that regulate T cell activation and function, including PD-1, CTLA-4, and TIM-3.
Immunotherapy: Treatment strategies that target the immune system to treat cancer and other diseases.
Antigen-specific therapies: Immune therapies that target specific antigens to induce antigen-specific immune responses.
Endogenous antigen processing and presentation: In this process, the antigen is processed by proteasomes and presented by MHC class I molecules. It occurs in almost all types of nucleated cells.
Exogenous antigen processing and presentation: This mechanism involves the uptake of extracellular antigens by antigen-presenting cells (APCs) such as macrophages, B-cells or dendritic cells, which then process and present the antigen to CD4+ T-cells with MHC class II molecules.
Cross-presentation: A process by which the professional APCs can present exogenous antigens with MHC class-I molecules to CD8+ T-cells.
T-cell receptor-independent antigen recognition: It is a rare event in which antigens can bind directly to MHC molecules and induce T-cell activation, without the need for TCR engagement.
Activation of natural killer cells (NK cells): NK cells can be activated by interactions between cell surface receptors on NK cells and MHC molecules on infected or stressed cells.
Non-classical antigen presentation: This involves the presentation of antigens by non-classical MHC molecules like CD1, MR1, and HLA-E molecules, which usually present lipid and metabolite antigens.
Viral immune evasion: Some viruses have evolved mechanisms to evade the antigen presentation process, and this can lead to ineffective immune responses.
Immunodominance: Some antigens are presented more effectively than others, and this can result in immunodominance of certain epitopes in the immune response.
Autoimmune disorders: In autoimmune diseases, self-antigens are presented by APCs and recognized by T-cells inappropriately, resulting in an autoimmune response.