Endotoxins and Types of Immunity

Endotoxins

• Composed of lipopolysaccharide (LPS), found only in Gram-negative bacteria.
• Toxicity arises from the Lipid A portion of LPS.
• Released upon bacterial death and cell wall lysis.
• Symptoms of exposure include fever, chills, hypotension, granulocytosis, and disseminated intravascular coagulation.
• Endotoxic shock is often a result of Gram-negative septicemia.

Types of Immunity

• Natural/Innate Immunity: Includes physical barriers (skin, urine flushing), and physiological barriers (vaginal acid pH).
• Adaptive/Acquired Immunity: Involves antibodies, complement system, memory B and T cells, categorized into:
  • Humoral Immunity: Action of antibodies in body fluids.
  • Cellular Immunity: T-lymphocytes directly attacking infected cells.

Invasion and Dissemination

• Invasion involves penetrating and growing in host tissues; varies by organism.
• Dissemination is the spread of pathogens to distant body sites, commonly through blood or lymph.

Routes of Transmission

• Airborne, food and waterborne, and vector-borne transmissions are key methods of pathogen spread.
• Examples: Anopheles mosquitoes transmit malaria; Aedes mosquitoes transmit dengue; cockroaches can spread diarrhea.

Types of Infections

• Local Infection: Confined to a specific area (e.g., boils, abscesses).
• Focal Infection: Originates locally, spreads to other areas (e.g., tonsillitis).
• Iatrogenic Infection: Resulting from medical procedures (e.g., post-surgery wounds).
• Systemic Infection: Spreads through blood and lymph.
• Opportunistic Infection: Occurs in immunocompromised hosts or when pathogens enter a different body part.
• Secondary Infection: Follows primary infection, exploiting a weakened immune system.
• Latent Infection: Clinically silent until reactivation occurs, potentially causing severe illness later.

Disease Classification

• Sporadic Disease: Occurs occasionally.
• Endemic Disease: Constantly present in a specific location or population.
• Epidemic Disease: Affects a large number of people rapidly.
• Pandemic Disease: Spreads across a larger region globally.

Effects of Infectious Disease

• Signs: Objective, measurable changes in the host (e.g., temperature, swelling).
• Symptoms: Subjective experiences reported by the host (e.g., pain, fatigue).

Immune Defense Mechanisms

• Physical barriers include skin and mucosal surfaces.
• Cleansing Mechanisms: Cough/sneeze reflex, nasal hair, cilia in the respiratory tract.
• Antimicrobial Substances: Lysozymes destroy bacterial cell walls; bile salts disrupt membranes.

Microbial Flora

• Indigenous microbiota are normal flora residing in or on the body.
• Types:
  • Resident Microbiota: Permanently inhabit and colonize areas for extended periods.
  • Transitory Microbiota: Temporarily inhabit a part of the body.

Toxins

• Classified as:
  • Exotoxins: Released by live bacteria; can cause severe damage even without bacterial death (includes cytotoxins, neurotoxins).
  • Endotoxins: Released from dying Gram-negative bacteria and can trigger strong immune responses.

Inflammation

• Protective response involving swelling, redness, heat, and pain, signaling potential tissue damage.
• Phagocytes, including neutrophils and macrophages, play crucial roles during inflammation.

Immune Response

• Essential for protecting against pathogenic microorganisms; can fail under immunocompromised states (radiation, chemotherapy).
• Provides memory to recognize and respond to future infections.