How do B cells know when to make antibodies?
B cells make antibodies when they ‘recognise’ the antigen (unique surface molecules) on a bacterium or virus. Every B cell makes only one type of antibody. Each type of antibody binds to only one type of bacterium or one type of virus. There are billions of different B cells in the body, but of these billions there is only a tiny number which can recognise any particular antigen. These few B cells can’t make enough antibody to protect you against disease. However, if the B cells which ‘recognise’ a particular antigen start to proliferate (multiply), then within a few days there will be enough B cells of that type to protect you against the disease (i.e. to agglutinate the bacteria or neutralise the virus.) B cell proliferation is due to Th cells. Th cells produce cytokines which tell B cells to proliferate. What happens to virus-infected cells? Tc cells (T cytotoxic cells) engage in hand-to-hand combat. They attack and destroy any cells which become infected with viruses. They do this
