The non-specific responses (Edexcel Int. A-level Biology)

This lesson describes the non-specific responses of the body to infection which include inflammation, lysozyme action, interferon and phagocytosis. The detailed PowerPoint and accompanying resources have been primarily designed to cover the content of point 6.8 of the Edexcel International A-level Biology specification but key details such as antigen-presentation are also introduced to prepare students for upcoming lessons on the immune response (6.9 & 6.10).

At the start of the lesson, the students are challenged to recall that cytosis is a suffix associated with transport mechanisms and this introduces phagocytosis as a form of endocytosis which takes in pathogens and foreign particles. This emphasis on key terminology runs throughout the course of the lesson and students are encouraged to consider how the start or end of a word can be used to determine meaning. The process of phagocytosis is then split into 5 key steps and time is taken to discuss the role of opsonins as well as the fusion of lysosomes and the release of lysozymes. A series of application questions are used to challenge the students on their ability to make links to related topics including an understanding of how the hydrolysis of the peptidoglycan wall of a bacteria results in lysis. Students will be able to distinguish between neutrophils and monocytes from a diagram and at this point, the role of macrophages and dendritic cells as antigen-presenting cells is described so that it can be used in the next lesson. The importance of cell signalling for an effective immune response is discussed and the rest of the lesson focuses on the release of two chemicals - interferons and histamine. During the interferon section, references are made to a previous lesson on HIV structure and action so students can understand how the release of these signalling proteins helps neighbouring cells to heighten their anti-viral defences. A step by step guide is used to describe the release of histamine in the inflammatory response and the final task challenges students to use this support to form a detailed answer regarding the steps in inflammation.