Cell Recognition + Immune System

• What is a pathogen?

  A microorganism which causes disease.
• What is immunity?


  The means by which the body protects itself from infection.
• What other molecules can the immune system identify other than pathogens?

  Cells from different organisms (transplant cells), abnormal body cells, toxins.
• What are the 2 types of white blood cells?

  Lymphocyte and phagocyte.
• What are the 2 types of lymphocytes?

  T-Lymphocyte and B-Lymphocyte.
• What is used to identify cells as self or non-self?

  The proteins on the cell-surface membrane.
• What is an antigen?

  Part of an organism or substance which is recognised as non-self and stimulates an immune response.
• What are the 2 types of defence?

  Specific and non-specific.
• What are the 2 types of non-specific defence?

  Physical barrier and phagocytosis.
• What is the role of a phagocyte?

  To ingest and destroy pathogens (phagocytosis).
• What is phagocytosis?


  The ingesting of large particles into vesicles by the cell-surface membrane.
• What attracts phagocytes?


  Chemical products of pathogens, or dead, damaged or abnormal cells.
• What allows phagocytes to recognise and attach to chemicals on the surface of the pathogen?

  Receptors on the cell-surface membrane.
• When the pathogen is engulfed, what is the vesicle called?

  A phagosome.
• What fuses with the phagosome?

  Lysosome.
• What do the lysosomes contain and what do they do to the pathogen?

  The lysosomes contain hydrolytic enzymes called lysozymes. These break down the pathogen.
• What happens after the pathogen has been digested in the phagosome?

  The soluble products are absorbed into the cytoplasm of the phagocyte.
• What are the 2 types of specific defence?

  Cell mediated response and humoral response.
• What type of cells are involved in cell-mediated response?

  T-Lymphocytes.
• Where are T-Lymphocytes made?

  The bone marrow.
• Where do T-Lymphocytes mature?

  The thymus.
• What type of cells are involved in humoral response?

  B-Lymphocytes.
• Where are B-Lymphocytes made?

  The bone marrow.
• Where do B-Lymphocytes mature?

  The bone marrow.
• What is cell mediated immunity?


  The response of T-Lymphocytes to foreign antigens presented on a body cell.
• What role do B-Lymphocytes play in the immune system?

  They are associated with the humoral immunity.
• What do T-Lymphocytes respond to?

  Antigen presenting cells.
• What is an antigen presenting cell?


  A cell which presents antigens which are foreign on their cell surface membrane.
• What is the role of a T-helper cell?


  It stimulates cytotoxic T-cells, B-cells and phagocytes.
• What is the role of cytotoxic (Tc) T-cells?


  They produce perforin to kill body cells that have been infected by viruses.
• What is meant by humoral immunity?


  The second stage of an immune response, in which B cells produce antibodies.
• What does a B cell have on its surface to fit the invasive antigen?


  A specific antibody. This antibody will only fit this antigen and vice versa.
• What does a B cell do to the antigen when it has attached to the antibody on its surface?


  It is taken in by endocytosis and then presented on the surface (it is an APC).
• How is a B cell stimulated to divide by mitosis?

  An activated Th cell binds to the processed antigens on the B cell to stimulate it to divide by mitosis, creating clones. This is clonal selection.
• What are the antibodies created from B cell clones described as?

  Monoclonal Antibodies.
• What can the B-Cell clones differentiate into?

  Plasma cells and memory cells.
• What do plasma cells do?

  Create specific antibodies during the primary immune response.
• What do memory cells do?


  During the secondary immune response, they differentiate into plasma cells to produce antibodies.
• What is an antibody?

  A protein created by a B-Cell, it has two identical, specific binding sites.
• What does an antibody do?

  It binds to a specific antigen, which is complementary to its specific binding site.