Overview of the immune response: two major groups of defences mechanisms. Skin & mucous membranes: rapidly regenerating surfaces, peristaltic movement, mucociliary escalator, vomiting, flow of urine/tears, coughing, lysosyme, sebaceous/mucous secretions, antimicrobial peptides, stomach acid, commensal organisms. Cellular and humoral defences: complement proteins, phagocytosis, macrophages, neutrophils, nk cells, no ros, cytokines. Cellular and humoral defences: antibodies, cytokines, t helper cells, cytotoxic t cells. As in the examples above, we can break the innate immune response into three categories: anatomical barriers physical barriers. Discussed in lecture 2 (just bellow!: humoral componenets at the anatomical barriers blood-borne factors. Cytokines: cellular components innate cells defeneders. Microbial encounters happen at mucosal surfaces: any surface potentially open to environemnt. Lysozomes in tears can dissolve cell walls of bacteria within the eye. Lining the trachea is mucus and cilia which suspend invaders and drive them out of the airway. The stomach is fairly acidic and limits growth of some bacteria.