antigen

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Immunogen, antigen, epitope, hapten:

Immunogen, antigen, epitope, hapten Dr.Gogoi University of Fiji

Immunogen, antigen, epitope, hapten:

Immunogen, antigen, epitope, hapten Immunogen: a stimulus that produces a humoral or cell-mediated immune response Antigen: any substance that binds specifically to an antibody or a T-cell receptor

Immunogen, antigen, epitope, hapten:

Immunogen, antigen, epitope, hapten All immunogens are antigens but not all antigens are immunogens Some very small molecules called haptens can bind to Ab’s or TCR’s but they cannot initiate an immune response…

Immunogen, antigen, epitope, hapten:

Immunogen, antigen, epitope, hapten Immunogen: a stimulus that produces a humoral or cell-mediated immune response Antigen: any substance that binds specifically to an antibody or a T-cell receptor Epitope: the portion of an antigen that is recognized and bound by an Ab or TCR/MHC complex ( aka antigenic determinant ) Hapten: a low molecular weight molecule that can be made immunogenic by conjugation to a suitable carrier

Immunogen, antigen, epitope, hapten:

Immunogen, antigen, epitope, hapten Paratope… Paratope: “The site in the variable (V) domain of an antibody or T-cell receptor that binds to an epitope on an antigen

The key event…:

The key event…

The basis of immunogenicity…:

The basis of immunogenicity… Foreignness Molecular size Chemical composition and heterogeneity Degradability

The basis of immunogenicity…:

The basis of immunogenicity… Foreignness Molecular size Chemical composition and heterogeneity Degradability

Presentation of processed antigen…:

Presentation of processed antigen…

There are two general classes of antigens:

There are two general classes of antigens Exogenous ( external ) Endogenous ( internal )

There are two general classes of antigens:

There are two general classes of antigens Exogenous: presented by A ntigen P resenting C ells (APC’s). These are macrophages, B-cells, and some dendritic cells Endogenous: typically peptides derived from any protein; an infected cell displays “not-self” proteins and is, thus, an “altered self cell”

There are two general classes of antigens:

There are two general classes of antigens Exogenous: these antigens are presented in MHC-II; they are seen by T-cells with a TCR and an associated protein called CD4 Endogenous: these antigens are presented by MHC-I; they are seen by T-cells with a TCR and an associated protein called CD8

There are two classes of T-cells:

There are two classes of T-cells T H have CD4 which interacts with MHC-II; thus, CD4 + T-cells are “MHC-II restricted.” T H cells are “helper cells” that send signals ( via cytokines and surface proteins ) to other cells of the immune system. The T H cells function as the “brain” of the immune system.

There are two classes of T-cells:

There are two classes of T-cells T C have CD8 which interacts with MHC-I; thus, CD8 + T-cells are “MHC-I restricted.” T C cells become cytotoxic T lymphocytes (CTL’s) which attack “altered self-cells ( e. g., infected cells.) “Altered self-cells” are also called “target cells.” They are the targets for the CTL’s cytotoxicity.

Experimental systems… viz. “haptens”:

Experimental systems… viz. “haptens” Hapten: a low molecular-weight molecule that can be made immunogenic by conjugation to a suitable carrier…

Haptens…:

Haptens…

Haptens…:

Haptens…

PowerPoint Presentation:

Antigen Processing

PowerPoint Presentation:

T cells do not recognise native antigens Y Y B Y Y Y Y Y Y Y B Y T Y T Proliferation and antibody production No proliferation No cytokine release Cross-linking of surface membrane Ig Y B Y B Y B Y B Y B Y B Y B

PowerPoint Presentation:

Cell surface peptides of Ag Antigens must be processed in order to be recognised by T cells Y T T cell r esponse No T cell response No T cell response No T cell response No T cell response Soluble native Ag Cell surface native Ag Soluble peptides of Ag Cell surface peptides of Ag presented by cells that express MHC antigens ANTIGEN PROCESSING

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