HOST

• Republic of the Philippines
• North Eastern Mindanao State University
• Tagbina, Surigao del Sur
• Unit III: Infection and Host Resistance
• Lesson B: Host Response to infection
• Host Response to infection

  • Non-specific host resistance
  • Specific host resistance
  • Vaccines in the elimination of disease
• Intended Learning Outcome: The students will be able to discuss immunity and its efficacy.
• Non-specific Host Resistance:
• Natural Barriers Against Infection

  • Skin
  • Mucous Membranes
  • Respiratory Tract
• Skin


  Acts as a formidable barrier against invading microorganisms, unless physically disrupted (e.g., by arthropod vectors, injury, or surgical incision)
• Mucous Membranes


  Many are bathed in secretions with antimicrobial properties, such as lysozyme, immunoglobulins (IgG and secretory IgA), and proteins that bind iron
• Respiratory Tract


  Has upper airway filters, and the mucociliary epithelium transports invading organisms away from the lung. Alveolar macrophages and tissue histiocytes in the alveoli engulf these organisms, but these defenses can be compromised by large numbers of organisms, air pollutants, or inborn defects
• Specific Host Resistance:
• Adaptive Immune Responses


  • Antibodies
  • Lymphocytes (T cells and B cells)
  • Cell-Mediated Immunity
  • Humoral Immunity
  • Memory Cells
• Antibodies


  Proteins produced by B lymphocytes that specifically recognize and neutralize pathogens
• Lymphocytes


  T lymphocytes (T cells) directly attack infected cells, while B lymphocytes (B cells) produce antibodies
• Cell-Mediated Immunity


  T cells orchestrate immune responses against intracellular pathogens
• Humoral Immunity


  B cells secrete antibodies into the bloodstream to combat extracellular pathogens
• Memory Cells


  After an initial encounter with a pathogen, memory T and B cells "remember" it, allowing faster and more effective responses upon subsequent exposure
• Vaccines in the Elimination of Disease:
• Vaccines


  Stimulate the immune system to recognize and remember specific pathogens without causing the actual disease, inducing the production of memory cells for a rapid and robust response if the individual encounters the pathogen later
• Herd immunity


  Achieved through widespread vaccination, reducing the overall disease burden in a population
• References: Bush, L. M. (2022). Host Defense Mechanisms Against Infection. Retrieved from Charles E. Schmidt College of Medicine, Florida Atlantic University. (Reviewed/Revised August 2022 | Modified November 2022)