Topic 2 C: Cells and The Immune System Flashcards
What do proteins do on the cell surface membrane?
act as antigens.
What do antigens do?
allow the immune system to tell the difference between your own, healthy
body cells (known as ‘self’ cells) and ‘foreign’ invaders
What are antigens?
molecules (usually proteins) that can generate an immune
response when detected by the body
Where are antigens found?
usually found on the surface of cells, including all your body cells
What are foreign antigens?
Antigens that aren’t normally found in the body
What antigens does the immune system respond to?
foreign antigens
Antigens allow the immune system to identify:
Pathogens, Abnormal body cells, Toxins, Cells from other individuals of the same species
What are pathogens?
organisms that cause disease, e.g. bacteria, viruses and fungi.
All pathogens have antigens on their surface — these are identified as foreign
by immune system cells, which then respond to destroy the pathogen.
What are Abnormal body cells?
Cancerous or pathogen-infected cells have abnormal antigens on their surface, which trigger an immune response.
What are Toxins?
- poisons
- they are molecules, not cells.
Some toxins are produced by bacteria, e.g. the bacterium Clostridium botulinum releases a protein toxin that affects the nervous system, causing the symptoms of botulism. The immune system can respond to toxins, as well as the pathogens
that release them.
What happens when you receive cells from another person, such as in an organ transplant
or blood transfusion?
cells will have some antigens that are different
to your own (unless the donor is genetically identical to you)
- foreign antigens trigger an immune response. This response leads to the rejection of transplanted organs if drugs aren’t taken to suppress the recipient’s immune system.
What are the most important antigens for blood transfusions?
ABO blood group antigens
What happens if the donated blood contains A or B antigens that aren’t recognised by the recipient’s immune system?
Antigens will generate an immune response.
What are the main stages of the immune response?
- Phagocytosis
- T-Cells
- B-Cells
- Antibody production
What is a phagocyte?
E.g macrophage
- is a type of white blood cell that carries out
phagocytosis (engulfment of pathogens)
Where are phagocytes?
found in the blood and in tissues and are the first cells to respond to an immune system trigger inside the body.
What does a phagocyte do?
recognises the foreign antigens on a pathogen
What does the cytoplasm of the phagocyte do.
Moves round the pathogen, engulfing it
- so pathogen is now contained in a phagocytic vacuole in cytoplasm of the phagocyte.
What does a lysosome do with the phagocytic vacuole?
- is an organelle that contains enzymes called lysozymes
- fuses with the phagocytic vacuole.
The lysozymes break down the pathogen
What happens after the lysosome fuses with rhe phagocytic cell.
phagocyte presents the pathogen’s antigens — it sticks the antigens on its surface to activate
other immune system cells.
- The phagocyte is acting as an antigen‑presenting cell.
What are T cells?
- also called a T-lymphocyte
- type of white blood cell
- has receptor proteins on its surface that bind to complementary antigens
presented to it by phagocytes. This activates the T-cell.
What do different types of T-cells do?
- respond in different ways.
- e.g helper T-cells (TH cells) release chemical signals that activate and stimulate phagocytes and cytotoxic T-cells (TC cells), which kill abnormal and foreign cells. TH cells also activate B-cells, which secrete antibodies
What are B cells
- also called B-lymphocytes
- type of white blood cell
- They’re covered with antibodies — proteins that bind to antigens to form an antigen-antibody complex.
What does each B cell have?
different shaped antibody on its membrane, so different ones bind to different shaped antigens