Immunity: Innate and Adaptive Overview

Innate Immunity

• Definition: The body's first line of defense against pathogens; non-specific and immediate response.
• Components:
  • Physical Barriers: Skin, mucous membranes.
  • Chemical Barriers: Antimicrobial substances (e.g., lysozyme, acidity).
  • Cellular Components:
    • Phagocytes: Macrophages, neutrophils.
    • Natural Killer (NK) Cells: Target virus-infected and tumor cells.
  • Inflammatory Response: Increases blood flow, recruits immune cells to sites of infection.
  • Complement System: Series of proteins that enhance phagocytosis and lyse pathogens.

Adaptive Immunity

• Definition: Specific immune response that develops over time; involves memory.
• Components:
  • Lymphocytes:
    • B Cells: Produce antibodies; responsible for humoral immunity.
    • T Cells:
      • Helper T Cells (CD4+): Assist other immune cells.
      • Cytotoxic T Cells (CD8+): Destroy infected cells.
  • Antibodies: Proteins that specifically recognize and neutralize pathogens.
  • Memory Cells: Long-lived cells that respond more rapidly upon re-exposure to the same pathogen.

Microbial Infections

• Types of Microbes:
  • Bacteria: Prokaryotic organisms; can be pathogenic or beneficial.
  • Viruses: Acellular; require host cells to replicate.
  • Fungi: Eukaryotic organisms; can cause infections in immunocompromised individuals.
  • Parasites: Organisms living on or in a host; can be unicellular or multicellular.
• Pathogenesis: Mechanisms by which microbes cause disease, including:
  • Adherence to host cells.
  • Invasion and colonization.
  • Toxin production.
  • Evasion of host immune response.

Pharmacological Treatments

• Antibiotics: Target bacterial infections by inhibiting growth or killing bacteria.
• Antivirals: Inhibit viral replication; often specific to certain viruses.
• Antifungals: Treat fungal infections; can target cell membrane or cell wall synthesis.
• Immunotherapy: Enhances or modulates the immune system; includes monoclonal antibodies and checkpoint inhibitors.
• Vaccination: Stimulates adaptive immunity to provide long-lasting protection against specific pathogens.

Immune System Disorders

• Hypersensitivity Reactions: Exaggerated immune responses; includes allergies and anaphylaxis.
• Autoimmune Diseases: Immune system mistakenly attacks the body's own tissues (e.g., rheumatoid arthritis, lupus).
• Immunodeficiencies: Reduced immune response; can be primary (genetic) or secondary (acquired, e.g., HIV/AIDS).
• Chronic Inflammation: Prolonged inflammatory response that can lead to tissue damage and disease (e.g., asthma, inflammatory bowel disease).

Innate Immunity

• First line of defense against pathogens; operates non-specifically and immediately.
• Physical Barriers: Includes skin and mucous membranes that block pathogen entry.
• Chemical Barriers: Comprise antimicrobial substances like lysozyme and acidic environments that deter microbes.
• Cellular Components:
  • Phagocytes: Such as macrophages and neutrophils that engulf and digest pathogens.
  • Natural Killer (NK) Cells: Target and destroy virus-infected and tumor cells.
• Inflammatory Response: Promotes increased blood flow and recruits immune cells to infected areas.
• Complement System: A series of proteins that enhance the ability of antibodies and phagocytic cells to clear microbes and damaged cells.

Adaptive Immunity

• Specific immune response that develops over time; capable of remembering past infections.
• Lymphocytes:
  • B Cells: Responsible for producing antibodies, key players in humoral immunity.
  • T Cells:
    • Helper T Cells (CD4+): Support various immune functions.
    • Cytotoxic T Cells (CD8+): Specialized in destroying infected cells.
• Antibodies: Proteins designed to specifically recognize and neutralize particular pathogens.
• Memory Cells: Long-lasting cells that enable a quicker immune response upon re-exposure to pathogens.

Microbial Infections

• Types of Microbes:
  • Bacteria: Prokaryotic organisms that can be harmful or beneficial to hosts.
  • Viruses: Acellular entities that rely on host cells for replication.
  • Fungi: Eukaryotic organisms that can infect immunocompromised individuals.
  • Parasites: Organisms that depend on a host for survival; could be unicellular or multicellular.
• Pathogenesis: The various mechanisms by which microbes cause disease, including:
  • Adhering to host cells.
  • Invading and colonizing host tissues.
  • Producing toxins.
  • Evading the host’s immune response.

Pharmacological Treatments

• Antibiotics: Effective against bacterial infections, either inhibiting growth or killing bacteria.
• Antivirals: Target and inhibit the replication of specific viruses.
• Antifungals: Treat fungal infections by disrupting cell wall or membrane synthesis.
• Immunotherapy: Modifies or enhances the immune response, including treatments like monoclonal antibodies and checkpoint inhibitors.
• Vaccination: Stimulates adaptive immunity, fostering long-lasting protection against targeted pathogens.

Immune System Disorders

• Hypersensitivity Reactions: Overreactions of the immune system, including allergic responses and anaphylaxis.
• Autoimmune Diseases: Conditions where the immune system attacks its own tissues, examples include rheumatoid arthritis and lupus.
• Immunodeficiencies: Diminished immune responses that can be primary (genetic) or secondary (acquired, e.g., from HIV/AIDS).
• Chronic Inflammation: Ongoing inflammation that can cause tissue damage and lead to diseases like asthma and inflammatory bowel disease.

Immunity

• The body's ability to resist or eliminate pathogens, such as bacteria, viruses, fungi, and parasites.
• Innate Immunity:
  • Acts as the first line of defense, offering a non-specific response.
  • Comprises physical barriers like skin and mucous membranes, and immune cells such as phagocytes and natural killer cells.
  • Key features include the inflammatory response and the complement system, which enhance the immune defense.
• Adaptive Immunity:
  • Provides a specific response to pathogens with the involvement of lymphocytes.
  • B cells produce antibodies that neutralize pathogens, while T cells have helper and cytotoxic roles.
  • Memory cells formed during the initial exposure allow for a faster response to subsequent infections.
• Key Components:
  • Antibodies: Proteins from B cells that specifically target and neutralize pathogens.
  • Antigens: Unique molecules found on pathogens that are recognized by the immune system as threats.
  • Cytokines: Proteins that regulate and mediate immune responses and inflammation.
• Vaccination:
  • Introduces a harmless version of a pathogen to stimulate the adaptive immune response.
  • Helps create memory cells, ensuring a quicker and more effective response on future encounters.

Microbiology

• The scientific study of microorganisms, encompassing bacteria, viruses, fungi, and parasites.
• Microorganisms:
  • Bacteria:
    • Single-celled prokaryotic organisms that can be beneficial (e.g., gut flora) or pathogenic (causing disease).
    • Reproduce asexually via binary fission, classified into types such as Gram-positive, Gram-negative, anaerobic, and aerobic.
  • Viruses:
    • Acellular entities that require host cells for replication, consisting of nucleic acid (DNA/RNA) and a protein coat.
    • Cause diseases by invading host cells and hijacking their machinery for reproduction.
  • Fungi:
    • Eukaryotic organisms that can be unicellular (yeasts) or multicellular (molds).
    • Essential for decomposition and nutrient cycling; some species are pathogenic, such as Candida and Aspergillus.
  • Parasites:
    • Organisms that live on or within a host, obtaining nutrients at the host's expense.
    • Includes protozoa, helminths (worms), and ectoparasites like lice and ticks.
• Microbial Pathogenesis:
  • Refers to the mechanisms through which microorganisms induce disease.
  • Includes factors like virulence factors (toxins, adherence properties) and host susceptibility which can influence disease outcomes.
• Microbiome:
  • Consists of the variety of microorganisms inhabiting specific environments, particularly the human body.
  • Plays a vital role in digestion, metabolism, and the regulation of the immune system.

Interrelationship Between Immunity and Microbiology

• The immune system is designed to detect and respond to microbial infections effectively.
• Microbial antigens serve as triggers for the adaptive immune response.
• Some successful pathogens possess the ability to evade or manipulate the immune responses, such as through antigenic variation.
• A solid understanding of microbiology is crucial for the development of effective vaccines and treatments targeting infectious diseases.

Test your knowledge on the two main types of immunity: innate and adaptive. This quiz covers the components, functions, and responses of both immune systems. Dive deep into the roles of phagocytes, lymphocytes, and the complement system.