The immune response (Edexcel A-level Biology A)

This fully-resourced lesson describes the roles of antigens, antibodies, B cells and T cells in the body’s immune response. The PowerPoint and accompanying worksheets have been designed to cover specification points 6.8 & 6.9 as detailed in the Pearson Edexcel A-level Biology A specification and includes descriptions of the involvement of plasma (effector) cells and macrophages as antigen-presenting cells.

In the previous lesson on the non-specific responses, the students were introduced to macrophages and dendritic cells as antigen-presenting cells and the start of this lesson challenges their recall and understanding of this process. Time is taken to discuss how the contact between these cells and lymphocytes is critical for the initiation of the body’s (specific) immune response. Moving forwards, a quick quiz competition is used to introduce the names of the different T cells that result from differentiation. Their specific roles are described including an emphasis on the importance of the release of cytokines in cell signalling to activate other immune system cells. T memory cells are also introduced so that students can understand their role in immunological memory and active immunity as described in an upcoming lesson covering point 6.12. The next part of the lesson focuses on the B cells and describes how clonal selection and clonal expansion results in the formation of memory B cells and effector cells. A series of understanding and application questions are then used to introduce the structure of antibodies and to explain how the complementary shape of the variable region allows the antigen-antibody complex to be formed. The lesson concludes by emphasising that the pathogen will be overcome as a result of the combination of the actions of phagocytes, T killer cells and the antibodies released by the effector cells.