Immune System

Immune System Overview

  • Daily Encounters with Microorganisms

    • Animal bodies encounter millions of microorganisms daily.

    • Microorganisms seek food and warm environments to live and reproduce.

    • While many microorganisms are harmless, some can cause illness.

  • Immune System Functionality

    • The immune system defends against pathogens, which are organisms capable of causing disease.

    • Its primary function includes distinguishing between self and non-self cells, facilitating the identification and destruction of potential pathogens.

    • Without the immune system, animals would be constantly diseased.

Types of Immunity

  • Innate Immunity

    1. External Innate Immunity (Barrier)

    • First Line of Immune Defense:

      • Skin

      • Mucous membranes

      • Respiratory system

      • Digestive system

      • Urinary system

    1. Internal Innate Immune Response

    • Serves as the second line of defense.

    • Characteristics of Internal Innate Immunity:

      • Rapid response

      • Non-specific destruction of non-self invaders

      • No immunological memory of past infections.

      • Present at birth

      • Utilizes physical, chemical, and cellular components for protection.

    • Inflammation:

      • A local reaction initiated by the innate immune system in response to trauma, infection, or chemical exposure.

      • Results in increased blood flow and white blood cell accumulation.

    • Phagocytosis:

      • The ingestion of pathogens by certain cells (e.g., macrophages and neutrophils).

  • Adaptive Immunity

    • Functions as the third line of defense.

    • Characteristics of Adaptive Immunity:

    • Targets specific organisms, slower to respond than innate immunity.

    • Develops and adapts over time as the animal matures and contacts various antigens.

    • An antigen is defined as any foreign substance that binds to lymphocyte receptors, inducing an immune response.

    • Capable of immunological memory.

    • Upon exposure to an antigen, the system utilizes:

      • Antibodies

      • Memory cells

      • Plasma cells

      • B lymphocytes

      • T lymphocytes

Subtypes of Adaptive Immunity

  • Humoral Immunity:

    • Activated by extracellular pathogens leading to antibody production.

    • B Lymphocytes:

    • Originate in bone marrow, migrate to lymphoid tissues.

    • Create antibodies facilitating phagocytosis and pathogen destruction, effective against extracellular pathogens.

    • Antibody Definition:

    • An immunoglobulin molecule synthesized in response to an antigen, specific to that antigen, leading to phagocytosis.

  • Cell-Mediated Immunity:

    • Mediated by T lymphocytes, does not rely on antibody production.

    • Provides immunity against intracellular pathogens (antigens on cell surfaces).

Active vs. Passive Immunity

  • Active Immunity:

    • Natural: Resulting from infection.

    • Artificial: Induced by vaccination.

  • Passive Immunity:

    • Natural: Involves maternal antibodies passed to the offspring.

    • Artificial: Involves the administration of monoclonal antibodies.

Immune System Functionality

  • Job: Keep out or eliminate pathogens (viruses, bacteria, parasites, fungi).

  • Characteristics of Immune Responses:

    • Non-specific (innate): No memory, rapid response.

    • Specific (adaptive): Memory, longer response time.

    • First Line of Defense: Physical barriers (skin, mucous membranes).

    • Second Line of Defense: Inflammatory response, phagocytes (e.g. neutrophils, macrophages).

Understanding Antigens and Immune Responses

  • Pathogen Location:

    • If outside the cell: B-cells produce antibodies (humoral response).

    • If inside the cell: T-cells mediate cell-mediated response.

  • B-cell Functionality:

    • Memory B-cells produce specific antibodies ensuring a rapid response upon re-encountering antigens.

    • Effector (Plasma) cells produce antibodies.

  • T-cell Functionality:

    • T-cells respond to infected or cancerous cells through surface receptors and release perforins to eliminate affected cells.

Autoimmune Diseases

  • Definition: Diseases resulting from an immune attack against the individual’s own tissues, indicating defective tolerance of self-antigens.

  • Clinical Examples: Type I diabetes, perianal fistulas, pannus, immune-mediated hemolytic anemia/thrombocytopenia.

  • Treatment: Typically involves immunosuppression and/or symptomatic therapies.

Immunosuppression

  • Occurs when immune functions or portions of the immune system are turned off due to:

    • Infection

    • Environmental factors (diet, stress, etc.)

    • Medications

  • Considerations: Immunosuppressed animals in treatment or hospitalization require special attention, particularly related to vaccination and client education.

Diagnostic Testing Methods

  • Antigen Tests: Detect actual organisms or parts, indicating that organisms are currently present.

  • Antibody Tests: Indicate prior exposure to organisms, potentially verifying whether the organism is present or absent.

Vaccination Considerations

  • Purpose: To help prevent infections by common viruses and bacteria, including zoonotic diseases.

  • Vaccine Definition: A suspension of living or inactivated organisms used as an antigen to stimulate immunity.

  • Administering Vaccines:

    • Understanding the features of infectious vs. non-infectious vaccines.

    • Stimulation of acquired immune responses through vaccination.

  • Infectious Vaccines:

    • Contain weakened antigens that can infect host cells, mimicking natural exposure for a more robust immune response.

    • Maternal antibodies can interfere with vaccination efficacy; vaccines should be administered properly, avoiding interference.

Specific Vaccines and Their Use

  • Types of Infectious Vaccines:

    • Included vaccines for: canine distemper, adenovirus, parvovirus, parainfluenza, Bordetella, feline leukemia, rabies, etc.

    • Immunity might be achieved rapidly post-vaccination (approximately 4 days) provided maternal antibodies are low enough.

  • Non-Infectious Vaccines:

    • Require adjuvants to enhance immune response due to not infecting host cells; reactions might occur more frequently.

  • Examples: Rabies, canine influenza, FIV, etc.

Adverse Vaccine Effects

  • Common adverse events may include:

    1. Local inflammation at injection sites (swelling, bruising).

    2. Systemic reactions such as lethargy, fever, and anorexia.

    3. Injection site reactions (e.g., lumps, hair loss).

    4. Allergic reactions (e.g., swollen eyes, potential anaphylaxis).

    5. Rare occurrences of tumor formation, especially in cats (adjuvant vaccines).

Documentation of Vaccinations

  • Records must comprehensively include:

    • Vaccine names, manufacturer, and lot numbers.

    • Expiry dates and administration details.

    • Important for identifying and managing adverse reactions.

Preventing Infectious Diseases

  • Methods to prevent infectious diseases include:

    1. Reducing exposure (quarantine, cleanliness).

    2. General health maintenance (nutrition, grooming).

    3. Specific immunity stimulation through vaccination.

    4. Disease treatment (e.g., using heartworm preventatives).

    5. Maintaining herd immunity through strategic vaccination.

Conclusion

  • 5 Rights of Drug Administration for Vaccines:

    1. Right patient: Healthy enough to respond, free from vaccinations contraindications.

    2. Right drug: Confirm vaccination is suitable for the patient.

    3. Right dose: Standardized dosages for all species.

    4. Right route: Ensure correct administration method (SQ, IM, IN).

    5. Right time: Assess if vaccinations are necessary at the current moment.