Ch1

• to defend against foreign invaders by generating a coordinated immune response

• innate (non-specific) • adaptive (specific)

• toxins • pollution • bacterial • virus • parasite • fungi

• to provide first line defence against pathogens

• non-specific • no memory • in-born

• physical • chemical • physiological • phagocytic

• respiratory tract => nasal hair –> remove inhaled particles => mucosal membrane and mucus –> mucosa secretes mucus which trap microbes –> microbes are removed by the beating of cilia on the epithelial cells, coughing and sneezing • skin => outer layer of dead skin with waterproof keratin protein –> prevent penetration of microbes • body fluids => urine and sweat can flush out microbes by the physical movement

• lysozyme (digestive enzyme) => present in tears and saliva => digest bacterial cell wall –> bacterial cell will soon lysed • sebum => secreted by sebaceous gland => unsaturated fatty acids inhibit the growth of bacteria and fungi due to a slightly acidic environment => over-production –> clog or block follicles –> inflammation –> pimple • acid => HCI in urine (uric acid), stomach (gastric acid) and vaginal secretion (lactic acid) –> acidic environment inhibit the growth of bacteria

• temperature => fever inhibit the growth of some pathogens and stimulate killer T cells which target virus-infected/abnormal/cancer cells • pH => low pH in stomach kills most microbes and destroy their toxins as it will be denatured under extreme pH => rapid pH change from the stomach to the upper intestine (2–>8) • normal flora => non-pathogenic bacteria lives on mucosal surface –> compete nutrients and attachment sites on epithelia –> pathogens have lower chance to survive

• chemical is the acid itself while physiological is the acidic environment

• lymphocytes • phagocytes

• neutrophils • monocytes (macrophages)

• most abundant kind of WBC • granulocytes circulating in the blood • move quickly to the infection sites and engulf pathogens

• able to present antigen on cell surface • activate T cells and immunity • engulf dead cells and microbes

• ameboid movement –> diapedesis (phagocytes squeeze to migrate out of blood vessels) • chemotaxis –> phagocytes move towards microbes due to the attraction of chemotaxins (histamine)

• attachment => phagocytes bind to microbes via their cell surface receptors • ingestion => microbes are injected by membrane invaginations (pseudopodia) and enclosed by phagosome • killing => lysosome fuse with phagosome forming phagolysosome –> release digestive enzymes –> microbes are killed • degradation => microbes are digested inside the phagolysosome –> digested products are released by exocytosis

• when innate defence mechanisms fail to stop the pathogens • it develops due to the exposure to various antigens

• works in antigen-specific manner to eliminate the antigen and provide prolonged protection for future challenge

• specific –> specialised response for best protection • diverse –> protection against various pathogens • memory –> enhanced response with repeated exposure • self and non-self discrimination –> lower autoimmunity

• big, round nucleus centered in the cell

• antigen-presenting cells (macrophages, B cells and dendritic cells) • lymphocytes (B and T cells)

• to activate T cells

• active natural –> infection • passive natural –> transfer of antibodies from mother to foetus via placenta • active artificial –> vaccination • passive artificial –> injection of ready-made antibodies

• active –> produce own antibodies • passive –> receives ready-made antibodies • artificial –> injection