Communicable diseases: specific immune system Flashcards
What is the specific immune system?
Known as active or acquired immunity, and is slower than non-specific immune response.
What are antibodies?
Y-shaped glycoproteins called immunoglobulins. Bind to specific antigens on the pathogen or toxin that has triggered a response.
Describe the structure of antibodies
2 long identical polypeptide chains called heavy chains, and two shorter identical chains called light chain. Chains held together by disulfide bridges. Disulfide bridges between the polypeptide chains, giving shape and strength.
How are antibodies specialised?
Bind to antigens with a protein ‘lock and key’ mechanism, as the antigens and antibodies binding site are complementary to each other. High specificity as the variable region is different for different antigens. The rest of the antibody is always the same, and is known as the constant region. Forms an antigen-antibody complex when joined.
How do antibodies work?
1) Antibody in an antigen-antibody complex acts as an opsonin. Complex is easily engulfed and digested by phagocytes.
2) Most pathogens can no longer effectively invade the host cells when part of the complex.
3) Antibodies act as agglutinins, causing pathogens carry antigen-antibody complexes to clump. This prevents the spread and easier to engulf many pathogens at once.
4) Antibodies act as anti-toxins, binding to toxins produced by pathogens, making them harmless.
Describe T helper cells
Have CD4 receptors on plasma membrane. Bind to surface antigens on APC’s. Produce interleukins (type of cytokine). Stimulate activity of B cells, increasing antibody production. Stimulates production of other T cells, and attracts macrophages.
Describe T killer cells
Destroy the pathogen. Produces perforin, making the plasma membrane permeable.
Describe T memory cells
live a long time and give immunological memory. Divide to form clones of T killer cells that destroy the pathogen, on second contact.
Describe T regulator cells
Suppress the immune system, control ®ulate. Stop immune response when pathogen eliminated, so self antigens are recognised, preventing autoimmune response. Interleukins help in this.
Describe plamsa cells
Produce antibodies and release them.
Describe B effector cells
Divide and form the plasma cell clones.
Describe B memory cells
Provide immunological memory. Programmed to remember a specific antigen and enable a rapid response when a pathogen is encountered again.
Give the process of cell-mediated immunity
1) Macrophages engulf and digest pathogens in phagocytosis. Process the antigens from the surface of the pathogen to form APC’s.
2) Receptors on some of the T helper cells fit the antigens. These are activated and produce interleukins, stimulating more T cells to divide rapidly by mitosis. Form clones of identical activated T helper cells that have the right antigen for a particular pathogen.
3) Cloned T cells:
develop into T memory cells, give rapid response in secondary.
produce interleukins for phagocytosis.
produce interleukins to stimulate B cells to divide.
develop into T killer cells and destroy infected cells.
Give the process of humoral immunity
1) Activated T helper cells bind to the B cell APC. This is clonal selection - B cell with the correct antibody to overcome a particular antigen is selected.
2) Interleukins produced by activated T helper cells activate B cells.
3) B cells divide by mitosis to give clones of plasma cells and b memory cells. Clonal expansion.
4) Cloned plasma cells produce antibodies that are complementary to antigens on surface of pathogen. Bind to antigen and disable, or act as opsonins/agglutinins. Primary immune response.
5) Some cloned B cells form B memory cells. These help in a rapid response if the pathogen is encountered again. This is the secondary immune response and is much faster.
What are autoimmune diseases?
Immune system does not recognise ‘self’ immune cells and attacks them. Immunosuppressant drugs are treatments which reduce the effects, but cannot cure them.
