Cells: The immune system Flashcards
What is an antigen
They are foreign chemical markers (usually proteins) on the surface of a cell membrane or viral particles that can generate an immune response
What do antigen allow the immune system to identify
- Pathogens
- Abnormal body cells (Cancerous or pathogen-infected cells)
- Toxins (Poison)
- Cells from other individuals of the same species (from blood/organ transplants of diff blood types)
What several defence mechanisms do our bodies have against pathogens
*Preventing entry:
- Inflammation:
- Recognising ‘foreign’ cells
State the difference between specific and non-specific immune response
- Specific immune responses protects the body against specific pathogens as the responses are tailored to the particular pathogen
WHEREAS
- Non-specific immune response is the same for all pathogens
Outline the first line of defences our body has
- The skin - acts as a barrier preventing bacteria from getting in AND secretes enzymes (found in sweat) that can kill bacteria
- The lungs - secretes mucus which traps pathogens and removes it through the ciliated epithelial cells
- Stomach - secretes hydrochloric acid that kills pathogens
- Eyes - secretes tears that contains enzymes that digest pathogens
- Blood - contains white blood cells that eliminate pathogens
List how pathogens are spread
- Food and water
- Insect bite
- Direct contact
- Indirect contact
- Airborne droplets
What are the main stages of the immune response
- Phagocytosis
- Cell mediated response (T-lymphocytes)
- Humoral response (B- lymphocytes , antibody production)
Describe what occurs during phagocytosis
- A phagocyte recognises the foreign antigen on a pathogen AND phagocyte the binds to the pathogen via receptors
- THEN the cytoplasm of the phagocyte move around the pathogen - engulfing it via endocytosis WHICH forms a phagosome (a phagocytic vacuole)
- AFTER the lysosomes fuse with the pathogen and the lysozymes break down the pathogen into soluble materials
- THEN the phagocyte presents the pathogens antigens on its surface t o activate other immune system cells AND the phagocyte is acting as an antigen-presenting cell
What is endocytosis
It is a cellular process in which substances are brought into the cell
What are the two types of white blood cells
- T-lymphocytes (T-cells)
- B-lymphocytes (B-cells)
What response are T cells involved in
The cell mediated response
What response are B cells involved in
The humoral response
Describe what happens in the cell mediated response
- T-cells have receptor proteins on its surface that minds to complementary antigens presented to it by phagocytes
- THIS activates the T-cell and stimulates the differentiation of the T-cells AND/OR undergoes clonal expansion (mitosis)
- T-cells differentiate into helper T-cells, cytotoxic T-cells and memory T-cells
- Helper T-cells also activate B-cells allowing then to undergo clonal selection
State the function of helper T-cells and what they are
- They are a type of immune cell
- They release chemical signals that activate and stimulate phagocytes and cytotoxic T-cells
- They also activate B-cells
State the function of cytotoxic T-cells and what they are
They are a type of immune cell which kill abnormal and foreign cells
What are antibodies
Proteins that have binding sites that are commentary to the antigens (to form antigen-antibody complexes) AND destroys the pathogen by releasing substances e.g perforin
Describe what happens in the humoral response
- B-cells (covered in antibodies) binds to an antigen complementary to the shape of the antibody on its surface (clonal selection)
- The pathogen is endocytosed (engulfed) , and the antigen presented on the plasma membrane
- Helper T-cells binds to the presented antigen (now on the surface of the B-cell) WHICH stimulates the B-cells to divide by mitosis (clonal expansion) and differentiate into plasma cells and memory B-cells
What are plasma cells
A type of immune cell that makes large amounts of a specific antibody
What are the antibodies that plasma cells secrete called
Monoclonal antibodies
How many binding sites does an antibody have (and how is it relative to the amount of foreign antigens it can bind to)
Two - it can bind to two foreign antigens at the same time causing the pathogens to become clumped together
What is agglutination
The clumping together of cells or particles caused by antibodies which assists phagocytosis
Why is agglutination beneficial
It allows phagocytes to bind to the antibodies and phagocytose many pathogens at once - which leads to the destruction of pathogens which carry the antigen
What region stays the same in antibodies
The constant regions
What does the specificity of an antibody depend on
The variable region - which has a unique tertiary structure (due to the different amino acid sequencing
What region of an antibody forms antigen binding sites
The variable region
What is the primary immune response
When an antigen enters the body for the first time and activates the immune system
What is the secondary immune response
When the same pathogen enters the body again, producing a quicker and stronger immune response
Why does the immune system produce a quicker, stronger response during the secondary immune response
- Clonal selection happens faster
- Memory B-cells are activated and divide into plasma cells that produce the right antibody to the antigen
- Memory T-cells are activated and divide into the correct type of T-cells to kill the cell carrying the antigen
- THIS OFTEN HAPPENS BEFORE ANY SYMPTOMS BEGIN TO SHOW
What do T- and B-cells produce after being exposed to an antigen
Memory cells
State the role of memory T-cells
Remember the specific antigen and remember it for the second time around
State the role of memory B-cells
Record the specific antibodies needed to bind to the antigen
