Immunity Lecture 9

Immunity

• Immunity is the body's defense against infectious organisms and other invaders through the immune response
• The immune system is composed of special cells, proteins, tissues, and organs that defend against invaders and maintain health

Types of Immunity

• Non-specific (Innate) Immunity: acts against all invaders and is not specific to a certain group of micro-organisms
• Specific (Acquired) Immunity: develops during lifetime as a result of exposure to antigens and involves production of antibodies and specialized lymphocytes against specific antigens

Non-specific Immunity

• Skin is the first barrier and mechanism of non-specific defense
• Epithelial surfaces form a physical barrier that is impermeable to most infectious agents
• Sebaceous glands in the dermis provide an environment unsuitable for microbe survival
• Sweat glands secrete sweat that washes off infections and has a high salt content that dries microorganisms
• Flushing action of tears and saliva helps prevent infection of the eyes and mouth
• Saliva contains anti-bacterial properties due to lysozymes
• Movement due to peristalsis or cilia in the gastrointestinal and respiratory tract helps remove infectious agents
• Gut flora can prevent pathogenic bacteria colonization by secreting toxic substances

Specific Immune Response

• Found in two types: Naturally Acquired Immunity and Artificially Acquired Immunity
• Two mechanisms of adaptive immunity:
  • Humeral Immunity: involves cellular macromolecules in body fluids, targeting extracellular pathogens like bacteria
  • Cellular Immunity: involves activation of phagocytes, T-lymphocytes, and release of cytokines, targeting microbes that survive inside cells, such as viruses, fungi, protozoans, cancers, and intracellular bacteria, and plays a role in transplant rejection