Immune System Worksheet 1 Bio 221 Lecture

What is the function of the immune system?

A group of organs and cells that defends the body against pathogens, removes damaged cells, absorbs nutrients, and identifies and destroys abnormal or cancerous cells.

What are the components of the immune system?

The immune system includes white blood cells (leukocytes), lymphatic vessels, lymph nodes, the spleen, thymus gland, bone marrow, and MALT (mucosa-associated lymphoid tissue).

Name the 5 types of white blood cells and their basic functions.

Neutrophils –- Phagocytose bacteria and debris.

Lymphocytes—Include B cells, T cells, and NK cells; responsible for adaptive and innate immunity.

Monocytes— Become macrophages; engulf pathogens and dead cells.

Eosinophils–-Attack parasites and modulate allergic responses. Basophils—Release histamine and heparin during inflammation and allergies.

What are the functions of the lymph vessels?

They transport lymph, return excess interstitial fluid to the bloodstream, and help move immune cells throughout the body.

What are characteristics of lymph vessels?

Lymph vessels have thin walls, valves to prevent backflow, and resemble veins in structure.

What are lymph nodes?

Lymph nodes are small, bean-shaped organs that filter lymph and house lymphocytes to initiate immune responses.

Approximately how many lymph nodes are in the body?

There are about 600 to 700 lymph nodes in the human body.

What fibers and cells are present in lymph nodes?

Lymph nodes contain reticular fibers that trap particles and white blood cells, including:

• Lymphocytes – Recognise and respond to specific antigens.

• Macrophages—Engulf and destroy pathogens and debris.

• Dendritic cells – Capture antigens and present them to lymphocytes to activate immune responses.

What is MALT?

MALT (mucosa-associated lymphoid tissue) is lymphoid tissue that protects mucosal surfaces—such as those in the digestive, respiratory, urinary, and reproductive tracts—from pathogens.

What are specific types of MALT?

Specific types of MALT include tonsils, Peyer’s patches in the small intestine, and the appendix.

What are the functions of the spleen?

The spleen filters blood, removes old red blood cells, stores platelets, and activates lymphocytes to initiate immune responses.

Distinguish between red pulp and white pulp.

The red pulp filters blood and removes old red blood cells, while the white pulp contains lymphocytes and initiates immune responses.

What is the function of the thymus gland?

The thymus gland is where T lymphocytes (T-cell) mature and differentiate, allowing them to function properly in immune responses.

What is the role of thymosin?

Thymosin is a hormone that promotes the development and maturation of T cells.

Distinguish between nonspecific (innate) and specific immunity.

Innate immunity provides general, immediate defense with no memory, while specific (adaptive) immunity targets particular antigens and has memory for faster future responses.

→ “memory” refers to the immune system’s ability to remember a pathogen it has encountered before.

Name some components of the first line of defense.

The first line of defense consists of physical and chemical barriers such as skin, mucous membranes, tears, saliva, stomach acid, and normal microbiota that prevent pathogens from entering the body.

What are PAMPs and DAMPs?

: PAMPs (pathogen-associated molecular patterns) are molecules present on pathogens that signal infection, while DAMPs (damage-associated molecular patterns) are molecules released by injured or stressed cells to signal tissue damage.

What are PRRs (TLRs)?

Pattern recognition receptors (PRRs), such as Toll-like receptors (TLRs), are found on immune cells and detect PAMPs and DAMPs, triggering immune responses against pathogens or cell damage.

What cells have PRRs?

Macrophages, dendritic cells, and neutrophils have PRRs, allowing them to detect PAMPs and DAMPs and initiate immune responses.

What happens when PRRs are activated?

When PRRs are activated, they trigger immune responses, including inflammation, cytokine release, and activation of other immune cells to fight pathogens or respond to tissue damage.

What are the symptoms of inflammation and name two vasodilators.

The symptoms of inflammation are redness, heat, swelling, pain, and loss of function. Two vasodilators that contribute to these symptoms are histamine and bradykinin.

What is margination and diapedesis?

• Margination is when white blood cells stick to the walls of blood vessels at the site of infection.
  

• Diapedesis is when these white blood cells squeeze through the vessel walls to reach the infected or damaged tissue.

What are the steps of phagocytosis?

1. Chemotaxis – The phagocyte moves toward the pathogen.

2. Adherence – The phagocyte binds to the pathogen, sometimes aided by opsonins.

3. Ingestion – The pathogen is engulfed into a phagosome.

4. Digestion – The phagosome joins with a lysosome to form a phagolysosome, where the pathogen is broken down.

5. Exocytosis – Waste materials are expelled from the cell.

What is an opsonin?

An opsonin is a molecule, such as an antibody or complement protein, that coats a pathogen, making it easier for immune cells to recognise and engulf, thereby enhancing phagocytosis.

What is complement?

Complement is a group of plasma proteins that enhance immune responses by destroying pathogens (lysis), coating them for easier engulfment (opsonization), and promoting inflammation.

Name the 2 ways complement is activated.

Complement can be activated by the classical pathway, which depends on antibodies, or the alternative pathway, which is triggered directly by pathogen surfaces.

What is the action of interferon, and what secretes it?

Interferons are proteins secreted by virus-infected cells that signal nearby cells to produce antiviral proteins, helping prevent the spread of infection.

What is the hypoferremic response?

The hypoferremic response is when the body reduces the amount of iron in the blood during infection to limit bacterial growth, since many bacteria need iron to survive.

What is a pyrogen, and how does its secretion improve immune response?

A pyrogen is a substance that causes fever, either from pathogens or immune cells. Fever speeds up immune cell activity and slows the growth of pathogens, enhancing the body’s defense.

What are lymph vessels and what do they contain?

Lymph vessels are blind-ended tubes filled with lymph, a clear fluid derived from interstitial fluid.

How does lymph move through lymph vessels?

Lymph flows one way through vessels aided by valves, skeletal muscle contraction, and pressure changes during breathing.

What is the main function of lymph vessels?

They collect excess interstitial fluid from capillary beds and return it to the bloodstream.

• Example: About 30 L of fluid is filtered from capillaries daily, 27 L reabsorbed, and 3 L recovered by lymph vessels as lymph.

What are the functions of lymph vessels?

Lymph vessels pick up excess filtered fluid from capillary beds, absorb fats from the intestines and transport them to the bloodstream, and expose lymph to white blood cells for immune monitoring.

What are granulocytes and what are their types and functions?

Granulocytes are a type of white blood cell that contain granules in the cytoplasm.

Types:

• Neutrophils – Most abundant; phagocytise pathogens.

• Eosinophils – Red granules; involved in allergic reactions and parasitic infections.

• Basophils – Least abundant; release histamine and mediate allergic reactions.

What are agranulocytes, and what are their types and functions?

Agranulocytes are white blood cells without visible cytoplasmic granules.

Types:

• Monocytes – Become phagocytic macrophages and give rise to dendritic cells.

• Lymphocytes—Carry out specific immune responses, including B cells, T cells, and NK cells.

Where do granulocytes and agranulocytes come from?

Both granulocytes and agranulocytes are derived from hematopoietic stem cells in the bone marrow.

• Granulocytes develop from myeloid progenitor cells.

• Monocytes (agranulocytes) also come from myeloid progenitors, while lymphocytes come from lymphoid progenitor cells.

How much of the spleen is made up of red pulp?

Red pulp makes up about three-quarters (¾) of the spleen and is responsible for filtering blood and removing old red blood cells.

What are key features of the thymus gland?

The thymus gland shrinks with age (involutes) and secretes thymosin.

What is the difference between innate (non-specific) and adaptive (specific) immunity?

• Innate (non-specific) immunity: Present at birth, works immediately, does not require prior exposure, responds the same way to all pathogens, and does not improve with repeated exposure.

• Adaptive (specific) immunity: Develops after first exposure, is not effective at birth, targets specific pathogens, and improves with repeated exposure due to immune memory.