Adaptive immunity: Third line of defence Flashcards
Explain how adaptive immune system responds to a pathogen
Responds to a specific pathogen and remembers a primary response for future pathogen threats
- Antibody-mediated immunity (humoral) –> Involves B cells which are activated and multiply
- Cell-meditated immunity –> Involves T cells which multiplies into 1 of 4 cell types
Outline B cells and their function
- Made in the bone marrow
- Produces plasma and memory B cells
- Plasma cells: produce antibodies that interfere with antigen’s function –> phagocytes can then kill them
Describe the ways in which antibodies deal with antigens
- Neutralisation: antibodies bind to bacterial toxins and block their action
- Agglutination: formation of antigen-antibody complex –> activates phagocyte –> destroys antigen
- Precipitation: antibodies bind to soluble antigens –> become insoluble
What are memory B cells?
Remain in the lymph tissue and provide immunological memory
- The required antibody (to previously exposed antigen) will be produced faster and in large amounts
Outline the process of antibody mediated immunity
- Antigen presenting B cells/ macrophages move to lymph nodes
- They are inspected by Helper T cells that have antigen receptor
- H.T. cells release cytokines –> stimulates cloning of millions of B cells specific to antigen
- Millions of memory B cells are also cloned
- Activated B cells produce plasma cells that stay in lymph nodes
- Plasma cells secrete antigen-specific antibodies that move to blood and lymph to infected areas
- They form antigen antibody complex, inactivates pathogen/toxin
- The pathogen is destroyed depending on its type
- Inflammatory response is activated, attracting phagocytes –> clearing debris
Outline the four types of T cells and their function
Lymphocyte produced in bone marrow, MATURED in thymus
- Cytotoxic (killer) T cells: destroys foreign, infected, or abnormal host cells by binding with the cell and producing a toxic chemical –> ruptures the cell
- Helper T cells: secretes cytokines which stimulates the production of B and T cells, increased phagocyte activity, promotes inflammation
- Suppressor T cells: inactivates B and T cells after an infection has occurred
- Memory T cells: remains in the body to recognise later infections by the same antigen
Outline the process of cell-mediated immunity
- Foreign material is engulfed by macrophages –> displays the antigen attached to the MHC II molecules
- Antigen presenting macrophages move to lymph nodes and are examined by H.T. cells (w/ T cell receptor)
- The helper T cells activate the cloning of millions of cytotoxic and memory T cells specific to antigen
- C.T. cells leave lymph nodes to the site of infection. Their antigen receptor binds to antigen displayed on infected cell
- C.T. cells then release chemicals that destroy the cell and any pathogens in it
- The cytokines also increase inflammation and attract more macrophages –> who carry out phagocytosis –> help destroy pathogens and clean debris
- Some C.T. cells produce interferon that protects cells around an infected ell from viral invasion
- Once the infection has been defeated, suppressor T cells release other chemicals to stop C.T cells from action and replication
What’s self vs non-self
Self: all nucleated cells of the body posses unique and distinct surface molecules that identify as “self”
- function as identification tags and are called major histocompatibility complex molecules (MHC) [ set of cell surface proteins essential for identifying foreign ]
Non-self: any foreign substance that triggers the immune response is an antigen
Outline the two classes of MHC molecules
MHC I: in all nucleated body cells and allows T cells to recognise body cells and not attack itself
MHC II: found on surface of specialised cells, called antigen presenting cells
What are mast cells?
Body cell that produces histamine which triggers immune response
What are dendritic cells?
Type of phagocyte that becomes and antigen presenting cells. Links innate and acquired response
How do cells become antigen presenting cells?
- A bacterium engulfed by a macrophage, encased by a vacuole
- Lysosomes fuse with the vacuole and digest the bacterium
- Antigens from digested bacterium are presented with MHC II on cell surface
- Macrophage becomes antigen-presenting cell
What are cytokines and their role in the immune response?
Group of small proteins secreted by several types of cells, e.g. macrophages, helper T cells
- Interferons: produced to kill viruses
- Lymphokines: produced by lymphocytes –> attracts other immune cells to site of infection
