LECTURE 3: Relationship of Antigens to the Host

• AUTOLOGOUS ANTIGEN

• TISSUE SPECIFIC ANTIGEN

• SYNGENEIC ANTIGEN

• ALLOGENEIC / HOMOLOGOUS ANTIGEN

• XENOGENEIC / HETEROLOGOUS ANTIGEN

• SUPERANTIGEN

RELATIONSHIP OF ANTIGENS TO THE HOST:

AUTOLOGOUS ANTIGEN

Known as autoantigen

autoantigen

Autologous antigen is also known as?

AUTOLOGOUS ANTIGEN

Found within the same individual; not foreign

AUTOLOGOUS ANTIGEN

The body's immune system usually exercises tolerance to self antigens

AUTOLOGOUS ANTIGEN

In some situations, antibodies may be produced in response to normal self antigens → Autoimmune disease

Autoimmune disease

In some situations, antibodies may be produced in response to normal self antigens —> ____

(AUTOLOGOUS ANTIGEN)

AUTOLOGOUS ANTIGEN

Example: Insulin as autoantigen in type 1 diabetes

Insulin in type 1 diabetes

Example of autoantigen:

AUTOLOGOUS ANTIGEN

SEQUESTERED ANTIGEN

SEQUESTERED ANTIGEN

These are autologous antigens that do not usually come in contact with antibody-producing cells since they are inaccessible to antibody-forming tissues

Immune-privileged sites

• Eyes

• Testes, Ovaries

• CNS

Example of Sequestered Antigen:

SEQUESTERED ANTIGEN

Examples: Immune-privileged sites

• Eyes

• Testes, Ovaries

• CNS

TISSUE SPECIFIC ANTIGEN

Various organs contain antigens that are both common and unique to those organs.

TISSUE SPECIFIC ANTIGEN

These are proteins or molecules predominantly expressed in specific tissues or organs of the body.

TISSUE SPECIFIC ANTIGEN

Examples:

• Thyroglobulin

• Myelin Basic Protein

• Thyroglobulin

• Myelin Basic Protein

EXAMPLES OF TISSUE SPECIFIC ANTIGEN:

Thyroglobulin

protein produced by thyroid gland

(TISSUE SPECIFIC ANTIGEN)

Myelin Basic Protein

protein found in myelin sheath that surround the nerve cells

(TISSUE SPECIFIC ANTIGEN)

Hashimoto’s thyroiditis & Graves’ disease

Disease associated with thyroglobulin

(TISSUE SPECIFIC ANTIGEN)

Multiple sclerosis

Disease associated with Myelin Basic Protein

(TISSUE SPECIFIC ANTIGEN)

SYNGENEIC ANTIGEN

Found in individuals of an inbred strain (or between identical twins), who are genetically identical

SYNGENEIC ANTIGEN

Same genetic markers

SYNGENEIC ANTIGEN

An antigen that comes from a genetically compatible source

SYNGENEIC ANTIGEN

Example:

• Transplantation in Mice

• Twins

• Transplantation in Mice

• Twins

EXAMPLES OF SYNGENEIC ANTIGEN:

ALLOGENEIC / HOMOLOGOUS ANTIGEN

Known as alloantigen

alloantigen

Allogeneic / Homologous Antigen are also known as?

ALLOGENEIC / HOMOLOGOUS ANTIGEN

Antigens that are found on the surface of cells from individuals of the same species but with different genetic backgrounds, particularly in the context of MHC.

ALLOGENEIC / HOMOLOGOUS ANTIGEN

Forms alloantibodies

alloantibodies

Allogeneic / Homologous Antigen forms?

Organ Transplantation

EXAMPLE OF ALLOGENEIC / HOMOLOGOUS ANTIGEN:

ALLOGENEIC / HOMOLOGOUS ANTIGEN

Example:

• Organ Transplantation

ALLOGENEIC / HOMOLOGOUS ANTIGEN

Example:

• When an individual receives a transplant from a genetically different donor, the recipient's immune system can recognize the alloantigens present on the transplanted cells as foreign.

ALLOGENEIC / HOMOLOGOUS ANTIGEN

Example:

• This recognition can lead to an immune response against the transplanted tissue, potentially causing rejection of the transplant.

XENOGENEIC / HETEROLOGOUS ANTIGEN

Known as heteroantigen or heterophile antigens

• heteroantigen

• heterophile antigens

Xenogeneic / Heterologous Antigen is also known as?

XENOGENEIC / HETEROLOGOUS ANTIGEN

Antigens present in the tissues or cells of a different species that can trigger an immune response if transplanted or introduced into a human.

XENOGENEIC / HETEROLOGOUS ANTIGEN

Prefix “xeno-” means foreign or from another species.

XENOGENEIC / HETEROLOGOUS ANTIGEN

Example:

• Animal-to-Human Transplants

  • Pig organs → studied as potential sources for human transplants.

Animal-to-Human Transplants

EXAMPLE OF XENOGENEIC / HETEROLOGOUS ANTIGEN:

Pig organs

Studied as potential sources for human transplant.

(XENOGENEIC / HETEROLOGOUS ANTIGEN)

SUPERANTIGEN

They are a special class of microbial proteins (usually toxins) that cause massive, non-specific activation of T-cells, leading to an exaggerated immune response.

SUPERANTIGEN

Can interact with a much broader range of T cells, leading to a massive immune response causing cytokine storm causing selfdamage

SUPERANTIGEN

Examples:

• Staphylococcus aureus - Toxic Shock Syndrome Toxin-1, enterotoxin

• Streptococcus pyogenes - exotoxin

• Staphylococcus aureus

• Streptococcus pyogenes

EXAMPLES OF SUPERANTIGEN:

Staphylococcus aureus

Toxic Shock Syndrome Toxin-1, enterotoxin

(SUPERANTIGEN)

Streptococcus pyogenes

exotoxin

(SUPERANTIGEN)

AUTOLOGOUS ANTIGEN

Identify the Relationship of Antigens to the Host based on its example:

Insulin as autoantigen in type 1 diabetes

AUTOLOGOUS ANTIGEN: SEQUESTERED ANTIGEN

Identify the Relationship of Antigens to the Host based on its example:

• Immune-privileged sites

  • Eyes

  • Testes, Ovaries

  • CNS

TISSUE SPECIFIC ANTIGEN

Identify the Relationship of Antigens to the Host based on its example:

Thyroglobulin - protein produced by thyroid gland

• Hashimoto’s thyroiditis & Graves’ disease

TISSUE SPECIFIC ANTIGEN

Identify the Relationship of Antigens to the Host based on its example:

Myelin Basic Protein - protein found in myelin sheath that surround the nerve cells

• Multiple sclerosis

SYNGENEIC ANTIGEN

Identify the Relationship of Antigens to the Host based on its example:

Transplantation in Mice: 2 genetically identical mice from an inbred strain

SYNGENEIC ANTIGEN

Identify the Relationship of Antigens to the Host based on its example:

Twins

ALLOGENEIC / HOMOLOGOUS ANTIGEN

Identify the Relationship of Antigens to the Host based on its example:

Organ Transplantation

XENOGENEIC / HETEROLOGOUS ANTIGEN

Identify the Relationship of Antigens to the Host based on its example:

Animal-to-Human Transplants

SUPERANTIGEN

Identify the Relationship of Antigens to the Host based on its example:

Staphylococcus aureus - Toxic Shock Syndrome Toxin-1, enterotoxin

SUPERANTIGEN

Identify the Relationship of Antigens to the Host based on its example:

Streptococcus pyogenes - exotoxin