8.2 Innate immunity

. Innate immunity Innate immunity is the natural phenomenon of resistance to infection which an individual possesses right from the birth. 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 Zoology Chapter XII Std Zoology Chapter Immunology The innate defense mechanisms are non-specific in the sense that they are effective against a wide range of potentially infectious agents. It is otherwise known as non-specific immunity or natural immunity. A number of innate defense mechanisms are operative non-specifically against a large number of microorganisms as shown in the Table . and Fig. . . Lysozyme in tears Removal of airbrone particles Physical barrier Low pH of vagina Rapid pH change Flushing of urinary tract Skin Bronchi mucus,cilia Gut acid Fig. . Various anatomical and physiological barriers to microbial attack