Outline the action of B lymphocytes following initial contact with an antigen or antigen presenting cell. (6 marks)

There are 4 stages to the response of B lymphocytes upon contact with antigens. These are antigen presentation, clonal selection, clonal expansion and differentiation. During antigen presentation the lymphocytes come into contact with the antigen or antigen presenting cell. The next stage is clonal selection where the B lymphocyte with receptors complementary to the antigens on the pathogen are selected. Following this clonal expansion occurs where the selected B cells divide by mitosis to produce many clones. Finally during differentiation the B lymphocytes differentiate to B plasma cells and B memory cells.