Specific and Non-Specific Defences

What is the main difference between non-specific and specific defenses in the immune system?

Non-specific defenses are the body's first line of defense against all pathogens, while specific defenses are directed at particular pathogens.

What are non-specific defences?

They are the body's initial defense against all pathogens, functioning through mechanisms such as skin, mucus, and immune responses.

What is the role of skin in non-specific defenses?

Skin serves as an effective barrier that prevents the entry of microorganisms, as long as it is not cut or broken.

What are sebaceous glands?

These are oil glands in the skin that produce sebum, which helps kill some pathogenic bacteria.

How does sweat contribute to non-specific defenses?

Sweat contains salts and fatty acids that prevent the growth of many microorganisms.

What do mucous membranes do?

They line body cavities that open to the exterior and secrete mucus to inhibit the entry of microorganisms.

What function do hairs serve in the respiratory system?

Hairs in the nose capture particles inhaled while breathing, trapping up to 90% of them.

What is the purpose of cilia in the respiratory system?

Cilia move mucus containing trapped particles toward the throat for coughing or swallowing, assisting in removing pathogens.

What role do acids play in the immune system?

Acids kill many bacteria taken in with food or present in swallowed mucus.

What is lysozyme, and where is it found?

Lysozyme is an enzyme that kills bacteria and is found in tears, saliva, and other bodily secretions.

What is the function of cerumen?

Cerumen, or ear wax, protects the outer ear from bacterial infections.

How do body fluids act as flushing agents?

Body fluids like urine can help keep areas free of pathogens by preventing bacterial growth.

What are the four protective reflexes against infection?

Sneezing, coughing, vomiting, and diarrhea help protect the body from infection.

How do phagocytes contribute to non-specific defenses?

Phagocytes engulf and digest microorganisms and cell debris, eliminating many pathogens.

What types of cells are known as phagocytes?

Monocytes, macrophages, neutrophils, and dendritic cells are all types of phagocytes.

What happens during the inflammatory response?

It reduces the spread of pathogens, destroys them, and begins the repair of damaged tissue.

What are the four signs of inflammation?

Redness, swelling, heat, and pain are the four signs of inflammation.

What is the role of mast cells in inflammation?

Mast cells release histamine to increase blood flow and permeability in response to tissue damage.

What does histamine do during the inflammatory response?

Histamine causes vasodilation and increases the permeability of blood capillaries, leading to redness and swelling.

What triggers fever in the body?

Fever is triggered by pyrogens that reset the hypothalamus's thermostat to a higher level.

What are some benefits of having a fever?

Fever can inhibit bacterial and viral growth and accelerate the body’s repair processes.

What is the lymphatic system?

It is a system consisting of lymph vessels, nodes, and organs that helps defend against pathogens.

What are lymph nodes?

Lymph nodes are clustered masses of lymphoid tissue that filter lymph and contain phagocytes.

What is the role of antibodies in the immune response?

Antibodies bind to specific antigens to inactivate them or mark them for destruction by phagocytes.

Define antigen. What role do they play in immunity?

Antigens are substances capable of triggering a specific immune response; they are typically foreign compounds.

What are B-lymphocytes?

B-lymphocytes are a type of white blood cell responsible for producing antibodies as part of the immune response.

How are T-lymphocytes involved in the immune response?

T-lymphocytes are responsible for cell-mediated immunity by directly attacking infected cells.

What is the difference between self and non-self antigens?

Self antigens are produced by the body and do not trigger an immune response, while non-self antigens trigger an immune response.

What two types of immunity are there?

Humoral (antibody-mediated) immunity and cell-mediated immunity.

What is the function of macrophages in the immune system?

Macrophages engulf and digest pathogens, and they also play a role in activating other immune cells.

What does the term 'phagocytosis' refer to?

Phagocytosis refers to the process by which phagocytes engulf and digest microorganisms.

What causes pus to form during an infection?

Pus forms from dead phagocytes, debris, and tissue fluid accumulating at the site of infection.

How do T-cells recognize infected cells?

T-cells recognize infected cells through specific antigen presentation on the surface of those cells.

What are the clinical implications of swollen lymph nodes?

Swollen lymph nodes may indicate an active infection as they increase lymphocyte production and filtering activity.

Why is good hygiene important in preventing infection?

Good hygiene practices, like handwashing, reduce the likelihood of pathogen transmission.

What is the role of mechanical barriers in the immune system?

Mechanical barriers like skin and mucous membranes prevent pathogen entry into the body.

What is immunization?

Immunization is the process of stimulating the immune system to develop a defense against specific pathogens.

What is quarantine, and why is it important?

Quarantine restricts movement of individuals to limit disease spread, especially from travelers arriving from infected areas.

What is the function of interleukin-1 during an infection?

Interleukin-1 is a pyrogen that influences the hypothalamus to raise body temperature during infection.

How do antibodies help in agglutination?

Antibodies cause particles to clump together, making them easier for phagocytes to capture and destroy.

What is the significance of 'itis' in medical terminology?

'Itis' denotes inflammation of specific organs or tissues, such as arthritis or bronchitis.

What does it mean for lymph nodes to become hyperplastic?

Hyperplastic lymph nodes increase in size due to an increase in lymphocyte production during infections.

How does the body return to its normal temperature after a fever?

The hypothalamus resets the temperature set point back to normal, leading to vasodilation and sweating.

What is the primary outcome when the immune system successfully eliminates a pathogen?

The successful elimination of a pathogen leads to recovery and often the development of immunity for future infections.

What are the steps in the humoral immune response?

• 1.Foreign invader (non-self antigen) reaches the lymphoid tissue

  2.Antigen-presenting cells detect and recognise the invader and present the antigen to specific B-cells which are activated/stimulated/sensitised

  1. 3.The antigen is also presented to helper T-cells, leading to release of cytokines (small proteins that are released in response to antigens and act as messengers in the immune response). Cytokines cause helper T-cells to clone themselves, to release different cytokines, which then activate B-Cells

  2. 4. B-Cells are stimulated to enlarge and rapidly divide via mitosis to produce clones

  3. 5.Most of the clones become plasma (effector) cells.

  4. 6. Plasma cells produce antibodies (with a specific active site) that are released into the blood, lymph and extracellular fluid until they reach the site of invasion.

  5. 7.The remaining cells become memory cells, which spread to all body tissues to allow the response to occur more rapidly should the antigen enter the body again.

What are the steps in the cell-mediated immune response?

• 1. Foreign invader (non-self antigen) reaches the lymphoid tissue

  2. Antigen-presenting cells detect and recognise the invader and present the antigen to specific T-cells, which are activated/stimulated/sensitised.

  3.Specific T-cells enlarge and rapidly divide via mitosis to form clone cells.

  4.Most clones become killer T-cells (cytotoxic cells) which migrate to the site of infection where they attach to the invading cells and secrete a chemical (cytotoxin) that destroys the antigen. They then seek more antigens to destroy.

  5.Other clones become helper T-cells, which play a role in humeral and cell-mediated immunity. They bind to the antigen on antigen-presenting cells and secrete cytokines.

  1. 6.Cytokines act by:

     • Attracting lymphocytes to the site of infection and cause them to become sensitised and activated which intensifies the response.

     • Attract macrophages to the site of infection so they can destroy pathogen/antigen via phagocytosis

     • Intensify phagocytotic activity of macrophages

     • Promote the action of killer T-cells

  2. 7. The remaining clones become suppressor T-cells, which act when the immune activity becomes excessive and the infection has successfully been dealt with. They release substances that inhibit B-cell and T-cell activity, slowing down the immune response.

What are the steps involved in the fever response?

• In case of rapid onset:

  1. 1. Hypothalamus responds to pyrogens by increasing the thermoregulatory ‘set point’ above the normal value

  2. 2. Person’s thermoreceptors detect the body temperature, and hypothalamus recognises that as lower than the new, higher set point

  3. 3. Person feels cold and, as a consequence, homeostatic mechanisms such as vasoconstriction, shivering etc occur

  4. 4. These responses conserve heat & increase heat production, driving the body temperature up rapidly

  5. 5. Crisis (the point where the fever breaks), the hypothalamus changes the ‘set point’ back to normal

• In this situation person feels hot & appears flushed, as skin vasodilation & profuse sweating occurs

What are the steps involved in the inflammatory response?

1. 1. Mast cells: specialised cells that are present in most tissues.

   • They stimulate and coordinate inflammation by releasing chemicals.

   • When stimulated by mechanical damage or by local chemical changes, mast cells release histamine, heparin & other substances into tissue fluid

2. 2. Histamine: increases blood flow through the area due to vasodilation & causes walls of blood capillaries to become more permeable so fluid is filtered from blood.

   • Increased blood flow causes heat & redness, and escape of fluid from blood causes swelling

3. 3. Heparin: prevents clotting in immediate area of injury.

   • A clot of fluid around area does form & this slows spread of pathogen into healthy tissues

4. 4. Phagocytes are attracted by the chemicals released from mast cells, and complement system proteins.

   • Phagocytes, particularly neutrophils, actively consume micro-organisms & debris by phagocytosis

5. 5. Pain is felt due to stimulation of pain receptors by the abnormal conditions in the tissue

6. 6. Pus forms from dead phagocytes (filled with bacteria, debris & dead cells) & tissue fluid

7. 7. New cells produced by mitosis & repair of damaged tissue takes place

What are antigens?

Antigens are substances that can provoke an immune response, typically foreign molecules such as proteins, polysaccharides, or nucleic acids found on the surface of pathogens or infected cells.

How do antibodies recognize antigens?

Antibodies recognize antigens through specific binding to unique regions (epitopes) on the antigen's surface, allowing for targeted immune responses.

What is the role of antibodies in the immune response?

Antibodies neutralize pathogens, opsonize them for phagocytosis, and activate complement systems to enhance the immune response.