Immune Response

• A phagocyte is a type of white blood cell that carries out phagocytosis. They're found in the blood and in the issue and are the first cells to respond to an immune system trigger inside the body.
• Phagocytosis:

  • Phagocyte engulfs the pathogen.
  • Lysosome fuses with phagocytic vacuole.
  • Pathogen is hydrolysed and phagocyte presents antigens on it's cell-surface membrane.
• T-Cells: A type of white blood cell. It has receptor proteins on its surface that bind to complementary antigens presented to it by phagocytes. This activates the T-cell. Different types of T-cells respond in different ways.
• Helper T-cells release chemical signals that activate and stimulate phagocytes and cytotoxic T-cells, which kill abnormal and foreign cells. Helper T-ells also activate B-cells, which secrete antibodies.
• B-cells: A type of white blood cell. They're covered with antibodies- proteins that bind to antigens to form an antigen-antibody complex. Each B-cell has a different shaped antibody on its membrane.
• B-cells: when the antibody on the surface of a B-cell meets a complementary shaped antigen, it binds to it. The activated B-cell divides into plasma cells.
• Cellular Response: The T-cells and other immune system cells that they interact with for a cellular response.
• Humoral Response: B-cells, clonal selection and the production of monoclonal antibodies form the humoral response.
• Both types of immune response ( cellular and humoral ) are needed to remove a pathogen from the body.
• The Primary Response:

  When an antigen enters the body for the first time it acivates the immune system. The primar response is slow as there aren't many B-cells that can make the antibody needed. Eventually the body will produce enough of the right antibody to overcome the infection.

  After being exposed to an antigen, both T- and B-cells produce memory cells. These memory cells remain in the body for a long time. Memory T-cells remember the specific antigen and will recognise it a second time round. Memory B-cells record the specific antibodies needed to bind to the antigen.
• The Secondary Response:

  If the same pathogen enters the body again, the immune system will produce a quicker, stronger 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. The secondary response often gets rid of the pathogen before you begin to show any symptoms.