A-Level Biology The Immune System Notes

Alternative transcript:

a type of white blood cell. They're covered. with antibodies Each B-cell has a different shaped antibody on its membrane, so different ones bind to different antigens. 1) when the antibody on the surface of a B-cell meets a complementary shaped antigen, it binds to it 2) This, together with substances released from T-cells, activates the B-cell. This process is called clonal selection 3) The activated B-Cen divides into plasma cels 4.Plasma cells make more antibodies Plasma cels are identical to the B-cell. They secrete loads of 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 An antibody has 2 binding sites, so can bind to 2 pathogens at the same time. This means that pathogens become clumped together - this is called agglutination Pragocytes then bind to the antibodies + phagocytose many pathogens at once. This process leads to destruction of pathogens caming this antigen in the body Primary immune response 1) when an antigen enters the body for the first time, it activates the immune system 2) Primary response is slow because there aren't many B-cells that can make an antibod I needed to bind to it 3) Eventually the body will produce enough of the right antibody to overcome the infection infected person will snow symtoms of the disease meanwhile 4) After being exposed to the antigen, both T-cells and B-cells produce memory cells These memory cells remain in the body for a long time, memory T-ceus remember the specific antigen and will recognise it second time round Memory B-ceus record the specific antibodies needed to bind the autigen. 5) The person is now immune + their immune system has the ability to respono quickly to a second infection. secondary immune response 1) if the same pathogen enters the body again, the immune system will produce a quicker, stronger immune response - the secondary response. 2) clonal selection happens faster. memory &-cells are activated + divide into plasma cells that produce the right antibody to the antigen. Memory T-cells are activated + divide into the correct type of T-cells to kill the cell carrying the antigen 3) The secondary response often gets rid of the pathogen before you begin showing symtoms