Animal Husbandry and Health 4 (Immunology and disease management)

Definition of immunology

Immunology is the scientific study of the immune system, focusing on its structure, function, disorders, and interactions with pathogens and vaccines. It examines how body defenses are orchestrated to protect livestock from infectious diseases.

Explain 3 ways in which immunology is importnant in Livestock

• Disease Prevention: Understanding immunology aids in developing effective vaccines and treatment strategies to reduce livestock morbidity and mortality.

• Productivity Enhancement: Healthy animals have higher productivity in terms of milk yield, meat quality, and reproductive health.

• Antibiotic resistance: immunology offers alternative strategies for disease prevention that minimize antibiotic use, promoting a more sustainable approach to animal farming

Explain the functions of the Immune System (3)

1. Recognition:
• Detail: Immune cells distinguish self from non-self, crucial for targeting pathogens without harming the body’s own cells.
• Mechanism: Receptors on T cells and B cells bind to antigens on pathogens, initiating an immune response.

2. Defense Mechanisms:
• Physical Barriers: Skin and mucosal membranes prevent pathogen entry.
• Cellular Responses:
• Phagocytes: Engulf and neutralize invaders.
• NK Cells and Cytotoxic T Cells: Destroy infected or abnormal cells.
• Chemical Barriers: Secretions and proteins that deactivate or kill pathogens.

3. Memory:
• Detail: Post-exposure, the immune system creates memory cells that enable a quicker, more effective response to future infections.
• Benefit: Fundamental for the effectiveness of vaccinations and natural immunity development.

Explain the 3 main functions of innate and adaptive immunity

Innate Immunity Functions:
• Barrier protection through skin and mucosal surfaces.
• Phagocytosis where cells like macrophages engulf and digest pathogens.
• Inflammation to isolate and control infection sites.

Adaptive Immunity Functions:
• Production of antibodies by B-cells that neutralize specific antigens.
• Killing of infected cells directly through cytotoxic T-cells.
• Creation of memory cells that lead to quicker responses on re-infection.

What is innate immunity?

The first line of defense, offering a broad and immediate response to all pathogens.

Innate immunity - explain how physical barriers contribute to immunity

• Skin: Acts as a protective barrier that prevents pathogens from entering the body.

• Mucous Membranes: Line the respiratory, gastrointestinal, and genitourinary tracts, trapping pathogens and facilitating their removal from the body.

Innate immunity - explain how chemical barriers contribute to immunity

• Stomach Acid: Destroys bacteria and other pathogens that enter the stomach, providing a chemical barrier to infection.

• Enzymes and Antimicrobial Peptides: Found in saliva, tears, and other bodily fluids, these substances provide a biochemical defense by breaking down bacterial cell walls and disrupting the function of pathogens.

Innate immunity - explain how cellular defenses contribute to immunity (phagocytes)

Phagocytes:
• Types: Include macrophages and neutrophils
• These cells engulf and digest pathogens through a process known as phagocytosis. They are essential in the initial response to infections and also play a role in activating other immune cells by presenting antigens.
• Act as the first line of defense against infections, quickly responding to pathogens and clearing infections before they can spread.

Explain the role of monocytes and granulocytes in immunity

Monocytes:
• Serve as precursors to macrophages and dendritic cells; involve in phagocytosis and antigen presentation.
• Role in Immunity: Link between innate and adaptive immunity.

Granulocytes:
• Neutrophils: Fast-acting phagocytes, predominant in bacterial infections; release antimicrobial peptides. • Eosinophils: Target parasites and play key roles in allergic responses.
• Basophils: Least abundant but vital in mounting allergic reactions and releasing histamine.

What is adaptive immunity? What are the main components of adaptive immunity?

Adaptive immunity is the component of the immune system that is specifically tailored to recognize and remember previous encounters with pathogens, providing a highly specialized and enhanced response upon subsequent exposures.

Key Components of Adaptive Immunity:
• B-Cells
• T-Cells
• Antibodies

Lymphocytes: Explain the function of B-Cells T-Cells and Antibodies

• B-Cells: Responsible for producing antibodies that specifically target antigens. They play a critical role in humoral immunity, where antibodies neutralize pathogens or mark them for destruction.

• T -Cells :
• Helper T -Cells: Facilitate the activation of B cells to produce antibodies and enhance the function of other immune cells.
• Cytotoxic T -Cells: Directly kill cells infected by viruses and other intracellular pathogens.

• Antibodies: Proteins that specifically bind to antigens, neutralizing pathogens and facilitating their removal by other immune cells.

Antigen specificity and memory capabilities of T-Cells and B-Cells

B Cells:
• Function: Responsible for antibody production that neutralizes pathogens.
• Memory B Cells: Long-term immunity, crucial for vaccine efficacy.

T Cells:
• Antigen Recognition: T cells recognize specific antigens presented by antigen-presenting cells like macrophages, and B cells.
• Activation and Differentiation: Upon recognizing an antigen, T cells become activated and proliferate.
• Activate upon subsequent exposures to the same antigen,

Explain 5 roles that antibodies play in immunity

• Neutralization
• Antibodies bind to antigens on pathogens, blocking them from entering cells. • Prevents the pathogen from infecting host cells.

• Opsonization • Antibodies coat pathogens, marking them for destruction by immune cells. • Phagocytes (like macrophages) easily recognize and engulf coated pathogens.

• Agglutination
• Antibodies bind multiple pathogens, causing them to clump together. • Clumped pathogens are easier for immune cells to clear out.

• Complement Activation
• Antibodies trigger the complement system, leading to the destruction of pathogens.
• Complement proteins form pores in the pathogen’s cell membrane, causing it to burst.

• Blocking Toxins
• Antibodies bind to toxins, neutralizing them and preventing them from causing harm.

What is inflammation?

Inflammation is a complex biological response of vascular tissues to harmful stimuli, such as pathogens, damaged cells, or irritants. It is a protective response involving immune cells, blood vessels, and molecular mediators.

Infections (Pathogenic) or Physical Trauma (Non-pathogenic):

• Redness: Caused by the dilation of small blood vessels within the damaged area.

• Heat: More blood flow to the area increases temperature, which can inhibit the growth of some pathogens.

• Swelling (Edema): Accumulation of fluid as blood vessels become permeable, allowing immune cells to enter the site of infection or injury.

• Pain: Induced by the release of chemicals and increase sensitivity of nerve endings at the site of injury or infection.

Function and Role of Inflammation (3)

• Mobilization of Immune Cells: Primarily, inflammation serves to mobilize neutrophils, macrophages, and other immune cells to the site of infection or injury. These cells work to eliminate the pathogen and begin repair of the tissue.

• Barrier Formation: Helps to prevent the spread of infection.

• Initiation of Repair: Following clearance of pathogens, inflammation signals the start of the healing process.

What is passive immunity? What types of passive immunity are there (2)?

Passive immunity is the type of immunity acquired from another source without the immune system generating a response. It is "borrowed" and temporary.

Natural Passive Immunity:
• Occurs when antibodies are transferred from a mother to her baby through the placenta during pregnancy, and through breast milk after birth (Colostrum).

Artificial Passive Immunity:
• Involves the administration of antibodies to an individual, typically through injections. These antibodies are derived from the serum of an infected person or animal and are used to treat or prevent certain diseases like rabies, tetanus, or snake bites. (Immunoglobulin Therapy, Antivenom or Hyperimmune Serum. Not vaccines )

What is active immunity?

Active immunity results from the activation of the immune system by a pathogen, causing the production of antibodies and memory cells.

What is the difference between natural active immunity and artificial active immunity?

• Natural Active Immunity: Developed when a person is exposed to a live pathogen, develops the disease, and then recovers, leaving a pool of memory cells specific to that pathogen.

• Artificial Active Immunity: Achieved through vaccination where a modified form of the pathogen stimulates the immune system without causing serious illness.

How do vaccines work?

Vaccines simulate a natural infection by introducing antigens, which are parts or weakened versions of pathogens, into the body without causing the disease. This exposure prompts the immune system to develop an immune response, including the production of antibodies and the activation of T cells.

• Memory Development: Crucially, vaccines also lead to the formation of memory cells. These cells remember the specific antigens and are primed to respond rapidly and effectively if the body encounters the real pathogen in the future.

Types of vaccines (3)

Live Vaccines:
• Contain a version of the living microbe that has been weakened so it cannot cause disease in healthy people.
• Example: Bovine Viral Diarrhea Virus (BVDV) vaccines used in cattle.

Killed (Inactivated) Vaccines:
• Made from microorganisms that have been killed through physical or chemical processes. • Example: Rabies vaccine used in domestic animals.

Subunit Vaccines:
• Include only the antigens that best stimulate the immune system.
• Example: Hepatitis B vaccine for humans, which is relevant for veterinary applications in similar diseases.

How do pathogens evade immune system defenses? (3 ways)

Intracellular Hiding
• Pathogens hide within host cells • HIV: Immune suppression (destruction of CD4+ T-cells) and intracellular residency to evade immune surveillance.

Antigenic Variation
• Pathogens alter their surface proteins through genetic mutations or recombination, which changes their antigens
• Malaria: Uses antigenic variation to frequently change its surface proteins, avoiding the antibodies produced by the host.

Immune Suppression
• Pathogens secrete substances that directly inhibit immune function.

Disease example: Foot-and-Mouth Disease (characteristics;mechanism of infection:immune evasion;prevention and control)

Characteristics: FMDV is a highly contagious virus affecting clovenhoofed animals, including cattle, sheep, goats, and pigs. It belongs to the Picornaviridae family and is known for its rapid mutation rate, leading to various serotypes and strains.

Mechanism of Infection:
• Rapid Spread: FMDV spreads quickly through direct contact between animals, contaminated farming equipment, feed, and even via aerosolized secretions over long distances.
• Antigenic Variation: The virus frequently alters its surface proteins (antigens), which allows it to evade the host’s immune responses.

Immune Evasion:
• Molecular Mimicry: FMDV may mimic host molecules, confusing the immune system and preventing an effective immune response.
• Interference with Immune Signaling: The virus can disrupt the production and signaling of cytokines, which are crucial for initiating immune defenses.

Prevention and Control:
• Vaccination: Use of polyvalent vaccines to protect against multiple strains, despite challenges in updating vaccines to match circulating variants.
• Biosecurity: Implementation of stringent biosecurity measures to prevent disease introduction and transmission on farms.