ANTIGENS

KEY TERMS

Antigen: a substance that reacts with antibodies or sensitized T

Immunogen: any substance capable of inducing an immune response which leads to the sensitization of T cells and antibody production

Immunogenicity: the ability of an immunogen to stimulate a body’s response

Autoimmune responses: reactions to our own self antigens & the basis of autoimmune disorders

ANTIGENS & IMMUNOGENS

• ANTIGENS

  • May or may not be able to induce/elicit an immune response

  • Not always foreign molecules; can be from our bodies or self antigens

• IMMUNOGENS

  • All immunogens are antigens

ALL IMMUNOGENS = ANTIGENS NOT ALL ANTIGENS ARE IMMUNOGENS

FACTORS/CHARACTERISTICS OF IMMUNOGENCITY

Macromolecular Size

• Larger the molecular weight = more potent the immunogen

  • However, molecular shape affects this as well

• Needs to have at least 10,000 daltons to be recognized by the immune system

  • Most active immunogen are > 100,000 daltons

Foreignness

• The more unrelated a molecule is to the host/body = the more immunogenic it’ll be

• The more distantly related molecules are to the host, the more likely they’ll be recognized as being foreign by the lymphocytes

• The more taxonomically distant the immunogen is from the host = the more immunogenic it is

  • Ex. A plant protein is more likely to be immunogenic to an animal than a protein from another animal

• Autoantibodies (antibodies to self-antigens) are an exception to this

Chemical Composition & Molecular Complexity

• The more complex the molecule is = more likely to stimulate an immune response

• Proteins & polysaccharides are most effective immunogens

  • G

• Carbohydrates are less immunogenic

  • Smaller & simpler in structure

Ability to Be Processed

EPITOPES

• what stimulates

• Produces this against antibodies

• B

HAPTENS

• l