Overview of Immunity

Overview of Immunity

• Immunity protects the body from harmful pathogens (bacteria, viruses, fungi).
• A coordinated response from many cells and molecules is involved.
• The immune system identifies and eliminates pathogens.
• Immunity is categorized into innate and adaptive.

Innate Immunity

• Innate immunity is the body's initial defense against pathogens.
• It provides a rapid, non-specific response.
• Key components: physical barriers (skin, mucous membranes), phagocytic cells (macrophages, neutrophils), and natural killer (NK) cells.
• Innate responses recognize pathogen patterns, not specific molecules.

Adaptive Immunity

• Adaptive immunity is a specific and effective response to pathogens.
• Specialized cells recognize and target specific pathogens.
• Key components: lymphocytes (T cells, B cells), antibodies.
• Adaptive immunity has memory; faster and stronger responses upon re-exposure.

Key Immune Cells

• Macrophages: Phagocytose pathogens, present antigens to T cells.
• Neutrophils: Phagocytic cells, initial infection response.
• Natural Killer (NK) cells: Kill infected or cancerous cells via cytotoxic granules.
• T cells: Lymphocytes involved in cell-mediated immunity, recognize and kill infected cells or regulate responses.
  • Helper T cells (CD4+): Activate other immune cells (B cells, cytotoxic T cells).
  • Cytotoxic T cells (CD8+): Directly kill infected cells.
• B cells: Lymphocytes that produce antibodies.
  • Antibodies: Bind to pathogen antigens, marking them for destruction.

Antigen Presentation

• Antigens trigger immune responses.
• Cells like macrophages process and present antigens on their surface.
• This allows T cells to recognize and respond to pathogens.

Immune System Disorders

• Immunodeficiency disorders: Weakened or impaired immune system function.
• Autoimmune disorders: Immune system attacks body's own tissues.
• Hypersensitivity reactions: Overreactions to harmless substances, causing allergic responses.

Immune Responses

• Inflammation: Localized response to infection/injury; increased blood flow, swelling, pain; innate and adaptive immune cells involved.
• Complement system: Proteins enhancing immune responses, promoting inflammation and pathogen destruction.

Cytokines

• Cytokines are signaling molecules from immune cells, regulating immune responses.
• They coordinate different immune cell activities.
• Examples: interferons, interleukins, tumor necrosis factor.

Immune System Development

• Immune system develops throughout childhood.
• Exposure to pathogens (and vaccinations) strengthens the immune system.

Immunological Memory

• Adaptive immunity's remarkable feature.
• Past pathogen encounters create faster and more robust responses.
• Basis for vaccination strategies.

Vaccination

• Introduces a harmless pathogen form to stimulate an adaptive response.
• Creates memory cells, developing antibodies for future encounters.
• Prevents infections before symptoms arise.