Antigens and Immune Response Flashcards
What are antigens?
Molecules that can generate an immune response when detected by the body
Where are antigens found?
Surface of cells
What are foreign antigens?
Antigens that aren’t normally found in the body that the immune response usually responds to
What are pathogens?
Organisms that cause disease
What triggers an immune response?
Abnormal or foreign antigens
What are toxins?
Poisons that are molecules not cells
Describe the process of phagocytosis:
- Phagocyte recognises foreign antigens on pathogen.
- Cytoplasm of phagocyte moves round pathogen, engulfs it
- Pathogen now contained in phagocytic vacuole in cytoplasm of phagocyte.
- Lysosome fuses with phagocytic vacuole. Lysozymes break down pathogen.
- Phagocyte presents pathogen’s antigens. Acts as antigen presenting cell.
How is a T-Cell activated?
The antigens on the pathogen bind to the receptor proteins on the T-Cell forming an antibody-antigen complex.
What do helper T-cells do?
Release chemical signals that activate and stimulate phagocytes and cytotoxic T-cells. Activate B-cells.
What do cytotoxic T-cells do?
Kill abnormal and foreign cells
What do B-cells do?
Secrete antibodies
How is a B-cell activated?
Binding of an antigen to an antibody on the surface of a B-cell and substances released from helper T-cells.
What is this process called?
Clonal selection
What do activated B-cells divide into?
Plasma cells
What do plasma cells do?
Secrete loads of antibodies specific to the antigen.
What are monoclonal antibodies?
An antibody produced from a single group of genetically identical B-cells.
What is agglutination?
When pathogens become clumped together because the antibody has 2 binding sites. Phagocytes bind to these antibodies and phagocytose many pathogens at once.
What are antibodies?
Proteins
What makes an antibody specific?
Variable regions which have unique tertiary structures complementary to one specific antigen.
What is the cellular response?
T-cells and other immune system cells that they interact with, e.g. phagocytes, form the immune response.
What is the humoral response?
B-cells, clonal selection and the production of monoclonal antibodies form the humoral response.
What is the primary response?
When an antigen enters the body for the first time, it stimulates an immune response - the primary response. This is slow because there aren’t many B-cells to make the antibody needed for the antigen but will eventually overcome the infection. Person shows symptoms meanwhile. After being exposed T and B cells produce memory cells for the next infection.
What is the secondary response?
If same pathogen enters again, body will respond quicker and stronger. Clonal selection happens faster. Memory B cells activated and can divide. Memory T cells activated to kill. Often don’t show symptoms.
