phagocytosis, b cells and t cells

what is the immune system made up of?

• specialised cells that respond specifically to foreign objects and protect an individual from harm

what is involved in the humoral vs cellular immune response?

• cellular- phagocytes, pathogens, t-cells

• humoral- b cells, clonal selection, monoclonal antibodies

what potential cells are created during humoral?

• plasma cells

• memory b cell

what potential cells are created during cellular immune response?

• cytotoxic cells

• memory t-cells

• t-helper cell

what cells does the immune system detect?

• pathogens

• cells from other organisms

• abnormal body cells

• toxins

what are pathogens?

• organisms that cause disease

  • some pathogens are micro-organisms (such as bacteria and viruses

  • others are fungi or protists

examples of cells from other organisms?

• an organ transplant, which can induce an immune response

examples of abnormal body cells?

• cancerous cells

  • immune cells can detect the presence of cells in the body that are not functioning as normal

what are toxins?

• harmful substances produced by pathogens

• immune cells can detect the presence of toxins

why does the immune system respond to pathogens and other foreign bodies?

• due to the presence of antigens

what are antigens?

• foreign protein/molecules that can generate an immune response when detected by the body

• they are present on the cell surface membrane of all cells

  • they signal to the immune system if the cells are foreign

specificity of antigens?

• every cell has specific antigens

• the antigens bind to the complementary receptors on the cell surface membrane of the immune cells

self signals?

• not all antigens induce an immune response

• antigens can also signal if the cells are ‘self’ or they belong to the host organism

what is an antibody?

• a protein specific to an antigen, that is produced by b cells

how does the immune system respond to antigens?

• lysozymes break down the foreign cells

• phagocytosis of the foreign cells

• production of antibodies that bind to the antigens and inhibit the functioning of the foreign cells

what are phagocytes?

• type of white blood cell that carries out phagocytosis

• they are found in the blood and in tissues

• they are the first cells to respond to an immune system trigger inside the body

process of phagocytosis?

• a phagocyte recognises the foreign antigen on a pathogen

• the cytoplasm of the phagocyte moves round the pathogen, engulfing it

• the pathogen is now contained in a phagocytic vacuole (a bubble) in the cytoplasm of the phagocyte

• a lysosome fuses with the phagocytic vacuole and the lysozymes break down the pathogen

• the phagocyte then presents the pathogen’s antigen — it sticks the antigens on its surface to activate other immune system cells

activation of t cells?

• phagocytes activate t lymphocyte cells

  • this is because the receptors on the surface of the t-cell are complementary to the pathogen’s antigens on the surface of the phagocyte

what are 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

what are the different types of t cells?

• helper t cells: release chemical signals that activate b cells, stimulate phagocytes and activate cytotoxic t cells

• cytotoxic t cells: kill abnormal and foreign cells

what else do t cells activate?

• b cells, which secrete antibodies

what are b cells?

• another type of white blood cell

• they are covered with antibodies

• each b cells production has a different shaped antibody on its membrane. so different ones bind to different antigens

• b cells divide into plasma cells

what are antibodies?

• a protein with specific binding sites produced by B cell lymphocytes in response to the presence of the appropriate antigen.

• proteins that bind to antigens and form an antigen-antibody complex

what is clonal selection?

• in the body, there are many different b cells, each with a different receptor

• an antigen comes in

• only the b cells with a complementary receptor binds to it

• that specific b cell is ‘selected’

what is clonal expansion?

• the selected b cell is activated by a t helper cell

• it divides by mitosis to produce lots of identical copies of itself (plasma cells/clones)

  • the t-helper cell basically gives the b cell the green light that is able to produce antibodies against the antigen.

activation of b cells?

• when the antibody on the surface of the b cells production meets a complementary shaped antigen, it binds to it

• this, together with the substances released from the helper t cells, activates the b cell

  • this is called clonal selection

• the activated b cells production divides into plasma cells

what is the action of b cells called?

• the humoral response

what are plasma cells?

• they are identical to b cells

• they secrete many antibodies specific to the antigen - these are called monoclonal antibodies

  • they bind to the antigens on the surface of the pathogen to form lots of antigen-antibody complexes.

what are monoclonal antibodies?

• antibodies produced from cloned plasma cells

OR

• antibodies with the same tertiary structure as a B cell

what is agglutionation?

• agglutination clumps the pathogens together

• the pathogens are engulfed by phagocytes via phagocytosis

• the pathogens are destroyed