immunity

immunity Acquired immunity has two components – cell mediated immunity (CMI) and antibody mediated immunity or humoral immunity. . Cell mediated immunity When pathogens are destroyed by cells without producing antibodies, then it is Type of innate immunity Mechanism . Anatomical barriers Skin Prevents the entry of microbes. Its acidic environment (pH - ) retards the growth of microbes. Mucus membrane Mucus entraps foreign microorganisms and competes with microbes for attachment. . Physiological barriers Temperature Normal body temperature inhibits the growth of pathogens. Fever also inhibits the growth of pathogens. Low pH Acidity of gastric secretions (HCl) kills most ingested microbes. Chemical mediators Lysozyme acts as antibacterial agent and cleaves the bacterial cell wall. Interferons induce antiviral state in the uninfected cells. Complementary substances produced from leucocytes lyse the pathogenic microbes or facilitate phagocytosis. . Phagocytic barriers Specialized cells (Monocytes, neutrophils, tissue macrophages) phagocytose, and digest whole microorganisms. . Inflammatory barriers Tissue damage and infection induce leakage of vascular fluid, containing chemotactic signals like serotonin, histamine and prostaglandins. They influx the phagocytic cells into the affected area. This phenomenon is called diapedesis. Table . Innate immunity- types and mechanisms XII Std Biology-Zoology Chapter- XII Std Biology-Zoology Chapter- Human Health and Diseases