Lymphatic and Immune System Review

Lymphatic System

  • General Overview:
    • Consists of cells and biochemicals traveling in lymphatic vessels.
    • Supports fluid circulation and works closely with the cardiovascular system.
  • Functions:
    1. Transportation of Interstitial Fluid:
    • Removes excess fluid from interstitial spaces, returning it to the bloodstream.
    1. Lipid Absorption:
    • Absorbs fats from the digestive system and transports via specialized capillaries called lacteals.
    1. Immune Defense:
    • Protects the body against diseases, coexisting with microbials in the environment.

Immunity Overview

  • Types of Immunity:
    1. Innate Immunity:
    • Includes physical barriers (like skin), cellular components (like phagocytes), and biochemical defenses (like complement proteins).
    • Components:
      • Epithelial barriers (skin, mucous membranes)
      • White Blood Cells (e.g., Neutrophils, Eosinophils, NK cells)
      • Complement System - a series of proteins aiding the immune response.
    1. Adaptive Immunity:
    • Specific and involves lymphocytes (T cells and B cells) that retain memory to enhance responses to previously encountered pathogens.
  • Timeframe After Infection:
    • Innate components are active within hours.
    • Adaptive response takes days (B lymphocytes: hours, T lymphocytes: days).

Neutrophils

  • Classification: Granulocytes and phagocytes that react to inflammation and bacterial products through chemotactic signaling.
  • Role in Infection:
    • Increase during acute bacterial infections (called Neutrophilia).
    • Release cytotoxic substances:
      • Free radicals, defensins, elastase (proteolytic enzymes) that can damage tissues.

Monocytes and Macrophages

  • Monocytes: Migrate to tissues and differentiate into macrophages.
  • Macrophages:
    • More powerful phagocytes than neutrophils, capable of cleaning up dead cells and debris.
    • Functions include cytokine secretion and antigen processing. - Live for months to years and can proliferate at inflammation sites.

Natural Killer (NK) Cells

  • Role:
    • Kill virus-infected and tumor cells without prior exposure or specificity to an antigen.

Complement System

  • Components: Comprised of 20 plasma proteins.
  • Functions:
    • Enhance inflammation, recruit phagocytes (chemotaxis), directly lyse target cells, and opsonize pathogens to increase phagocytosis effectiveness.
  • Activation Pathways:
    • Classical Pathway: Triggered by antibody-antigen complexes.
    • Alternative Pathway: Mediated by microbial components.

Inflammation - Cardinal Signs

  1. Redness: Increased blood flow
  2. Swelling: Increased capillary permeability
  3. Heat
  4. Pain
  5. Loss of function

Virus Replication

  1. Virus enters a host cell.
  2. Outer coat stripped inside the cell.
  3. Viral nucleic acid released into the cell.
  4. Nucleic acid utilizes the host's machinery to produce more viruses.
  5. New viruses are assembled, often leading to host cell destruction.

Adaptive Immunity

  • Mechanism:
    • The specific system recognizes and destroys foreign invaders, retaining a memory of encounters for swift future responses.
  • Components: Largely mediated by lymphocytes, specifically B-cells and T-cells.

T Cells

  • Types:
    • T Helper Cells: Activate other immune cells, stimulate B-cell proliferation, and secrete pro-inflammatory cytokines.
    • Cytotoxic T Cells: Target foreign cells directly, including cancer and virus-infected cells.

B Cells

  • Function: Responsible for humoral immunity by producing antibodies.
  • Types:
    • Memory B Cells: Rapid response to previously encountered antigens.
    • Plasma B Cells: Produce specific antibodies upon activation but are typically short-lived.

Hypersensitivity Reactions

  • Type I Hypersensitivity:
    • Also known as allergy, caused by an excessive IgE response to allergens leading to symptoms like hives, asthma, and potentially anaphylaxis.