MICR290_Chapter 15_AFernando_part 1 LECTURE AUDIO

Chapter 15: Innate Immunity

Overview of Innate Immunity

• Innate immunity is the immunity that we are born with, providing a first line of defense against pathogens from the moment of birth.

• It includes immediate responses to pathogens that enter the body once a newborn is exposed during delivery and subsequent environmental exposure.

Newborn Immune Response

• At birth, a newborn is exposed to various microbes in the surrounding environment, including pathogens.

• Innate immunity acts as a primary defense mechanism against these infections, working to resist and combat potential illnesses.

Types of Immunity

• Acquired Immunity: Distinct from innate immunity; it develops over time through exposure to antigens. It is further divided into:

  • Active Immunity: Immunity that develops after exposure to a pathogen.

  • Passive Immunity: Short-term immunity acquired from another organism, like maternal antibodies.

Body's First Line of Defense

• Portals of Entry: Discusses how microbes can enter the body via various routes:

  • Skin: Major barrier against pathogens and first line of defense protection.

  • Mucous Membranes: Covering respiratory, digestive, urinary, and reproductive systems, serving as additional barriers.

• Extracellular Enzymes: Enzymatic responses that aid in microbial destruction.

  • Phagocytosis: The process by which certain cells ingest and eliminate pathogens.

Skin Structure and Function

• Skin consists of two layers:

  • Epidermis: The outermost layer providing a barrier.

  • Dermis: The underlying layer containing supportive structures.

• Skin serves as a physical barrier and contains various chemical defenses:

  • Sweat (Perspiration): Contains salt, which inhibits pathogenic growth due to its high salinity.

  • Antimicrobial Peptides: Secreted compounds that can destroy microbes; includes substances such as leukocidins, which are toxic to bacteria.

Important Chemical Defenses

• Lysozyme: An enzyme found in tears that destroys bacterial cell walls, aiding in microbial elimination.

• Sebum: Secreted by oil glands, maintaining skin moisture, pliability and lowering the skin’s pH to inhibit bacterial growth:

  • Sebum contributes to skin's slightly acidic environment, deterring pathogenic colonization.

Conclusion

• Overall, innate immunity is an essential initial defense system that employs barriers, enzymes, and other biochemical factors to prevent infections in newborns and throughout life.