cell recognition and the immune system Flashcards
What is an antigen?
Foreign protein on the cell membrane with a specific shape that stimulates an immune response.
What is a pathogen?
Microorganism that causes disease.
What is the role of the lysozyme in phagocytosis?
Lysozyme fuses with phagosome and releases hydrolytic enzymes to hydrolyse the pathogen.
Provide some examples of antigens.
Glycoproteins, toxin, abnormal cells.
Describe two ways pathogens cause disease.
Viruses - invade the cells and replicate, damage and kill.
Bacteria - produce toxins.
Why is phagocytosis considered considered a non specific immune response?
Doesn’t involve antigen recongition.
Explain the importance of an antigen presenting cell?
T-helper cells bind to it and stimulate the divide of other lymphocytes to help fight off infection.
Describe how a phagosome is formed.
Phagocytes engulf the pathogen and form a vesicle called a phagosome.
Explain the effect of antigenic variability.
Viruses mutate causing the antigens to change shape.
As a result it is no longer complementary to the variable region of the antibody.
Describe how phagocytosis of a virus leads to presentation of its antigens (3 marks)
Engulfing forms phagosome.
Phagosome fuses with lysosome.
Virus destroyed by lysozymes.
Antigens from virus are presented on the cell membrane.
Describe how presentation of a virus antigen leads to the secretion of an antibody against this virus antigen (3 marks).
T-helper cell binds to antigen.
Helps stimulate specific B-cell.
Divides by mitosis.
Forming plasma cells that release antibodies.
