Mechanisms for preventing pathogens from entering the body Mechanisms for initially dealing with any foreign substances present in body Mucous membranes and secretions Cilia in respiratory tract Lysozyme in tears, mucus and saliva- best against Gram positive invaders Commensal organisms colonize an area, fight off pathogens for the space and prevent them from growing there Cytokines Phagocytes Preventing blood loss Keratinised skin covering Flushing of the urinary tract Saliva flow Acidic condition in saliva and sweat, and especially stomach High salt content in sweat prevent non- osmotolerant microbes from growing Interferon Complement (proteins) Natural Killer (NK) cells Inflammation Fever -Low-weight proteins and glycoproteins that act as signalling molecules of the immune system that act locally, are short lasting and result in a variety of responses -An example of a cytokine that is usually released by virus-infected cells and signal neighbouring cells to prepare for viral infection Group of over 20 types of blood proteins (some are enzymes) that when activated result in a cascade of events that lyses pathogenic cells. -release of histamine from damaged cells causes phagocytes to be attracted to area, redness and swelling are symptoms -an increased temperature results in a quicker response and is an attempt to provide unsuitable environment for pathogen -platelets and blood proteins that become insoluble create a plug if tissue is damaged -cells that engulf and digest foreign material, includes granulocytes and macrophages -large granular lymphocytes that innately target virus-infected cells and cancer cells by releasing proteins that can cause lysis or induce apoptosis

1 st line of defence Mechanisms for preventing pathogens from entering the body 2 nd line of defence Mechanisms for initially dealing with any foreign substances present in body Non-specific immunity summary-solution Physical barriers Keratinised skin covering Mucous membranes and secretions Mechanical means Cilia in respiratory tract Flushing of the urinary tract Saliva flow Chemical means Lysozyme in tears, mucus and saliva- best against Gram positive invaders Peroxidases Acidic condition in saliva and sweat, and especially stomach High salt content in sweat prevent non- osmotolerant microbes from growing Presence of normal micro-biota (normal flora) Commensal organisms colonize an area, fight off pathogens for the space and prevent them from growing there Defensive molecules Cytokines-Low weight proteins and glycoproteins that act as signalling molecules of the immune system that act locally, are short lasting and result in a variety of responses Interferon-an example of a cytokine that is usually released by virus- infected cells and signal neighbouring cells to prepare for viral infection Complement (proteins)-group of over 20 types of blood proteins (some are enzymes) that when activated result in a cascade of events that lyses pathogenic cells Cellular defences Phagocytes -cells that engulf and digest foreign material, includes granulocytes and macrophages Natural Killer (NK) cells-large granular lymphocytes that innately target virus-infected cells and cancer cells by releasing proteins that can cause lysis or induce apoptosis Protective responses Inflammation-release of histamine from damaged cells causes phagocytes to be attracted to area, redness and swelling are symptoms Preventing blood loss -platelets and blood proteins that become insoluble create a plug if tissue is damaged Fever-an increased temperature results in a quicker response and is an attempt to provide unsuitable environment for pathogen