ANTIGENS AND ANTIBODIES

antigen

any substance capable of causing a specific immune response

what are antigens

large molecules such as proteins, carbohydrates, lipids or nucleic acids

other examples of antigens

virus particles, whole microorganisms, toxins, egg whites

where are antigens found and where do they work?

• in body fluids such as lymph, blood

• they work on the outside of the cell before the pathogen enters

self antigens

large molecules produced in a person’s body that do not cause an immune response

non-self antigens

foreign compounds that do trigger an immune response

what is an antibody?

a y shaped specialised protein that is produced by plasma cells

where are antibodies found?

in the plasma

when are antibodies produced?

in response to a non- self antigen

what are the 5 classes of antibodies

IgA, IgD, IgE, IgG, IgM

what does an antigen and antibody form?

combine to form antigen antibody complex (similar to lock and key model)

what is the role of antigen presenting cells?

1. present the antigens from the pathogen on the surface of their own cell membranes to be recognised by lymphocytes (B and T cells)

2. digest pathogens and break them into smaller fragments

what can an antigen presenting cell be?

macrophage, dendritic cells, undifferentiated B cells

How do antibodies work? (not really tested in SCSA)

• each antibody has a different mode of action

  1. bind to the pathogen to inhibit reactions with other cells and compounds

  2. bind to the surfaces of viruses, stopping them from entering the cell

  3. agglutinate bacteria, viruses to assist phagocytosis

  4. react with soluble substances to make them insoluble for easy phagocytosis

  5. coat bacteria so they are more easily consumed by phagocytes

  6. dissolve organisms