Immune System: Key Concepts in Physiology and Immunology

What is immunity?

The body's ability to protect itself.

What distinguishes 'self' from 'non-self'?

'Self' refers to healthy vs damaged vs infected cells; 'non-self' includes bacteria, viruses, parasites, allergens, etc.

What are the three lines of defense in the immune system?

1. Barrier Protection (first line), 2. Innate Immune Response (second line), 3. Active Immune Response (third line).

What characterizes the innate immune response?

It is rapid (minutes to hours), non-specific, and has no memory of pathogens.

What is the role of antigen-presenting cells (APCs)?

They activate the adaptive immune response.

What is the primary function of interstitial fluid?

It is the fluid outside of cells.

What is blood composed of?

Blood consists of plasma (liquid component) and various cells, including red blood cells and immune cells.

What is the lymphatic system's primary function?

It redistributes fluids and facilitates the immune system by transporting white blood cells.

What are the components of lymph?

Interstitial fluids, white blood cells (leukocytes), and no red blood cells (RBCs).

What is the site of production for all white blood cells?

Bone marrow.

Where do T cells mature?

In the thymus gland.

What is the function of the spleen in the immune system?

It stores white blood cells, controls blood cell levels, and filters out old RBCs.

What is the role of mucosa-associated lymphoid tissue (MALT)?

It samples the external environment and delivers information to immune cells.

What are physical barriers in the immune system?

Skin and mucosal/ciliated epithelia.

What are examples of mechanical protection in the immune system?

Mucous, sneezing, coughing, and intestinal secretions.

What are chemical barriers in the immune system?

Stomach acid (pH) and lysozyme destruction.

What is the role of phagocytic cells?

They consume foreign material like debris, fungal spores, and viruses/bacteria.

What are the steps of phagocytosis?

1. Recognize common features of foreign material, 2. Engulf material, 3. Digest material, 4. Release debris, 5. Raise alarm to immune system.

What are cytokines?

Signals released by phagocytes to attract and activate other immune cells.

What types of white blood cells are phagocytes?

Neutrophils and monocytes/macrophages.

What is the function of natural killer (NK) cells?

They scan and kill infected or harmful cells.

What is the major histocompatibility complex (MHC)?

A set of molecules displayed on cell surfaces that help the immune system recognize self-cells (MHC-I) and present antigens (MHC-II).

What happens if an NK cell detects MHC-I on a target cell?

The NK cell backs off and does not kill the target cell.

What is an epitope?

A piece of foreign material presented on the surface of a cell after phagocytosis.

What is the difference between innate and adaptive immune responses?

Innate is rapid and non-specific, while adaptive is slower, specific, and has memory.

What is the role of lymph nodes?

They connect lymphatic vessels and filter lymph fluid.

What is the function of lymphatic ducts?

They drain lymph into veins, specifically the subclavian veins.

What are Peyer's patches?

Areas in the intestines rich in M cells that sample ingested food for immune response.

What is the complement system?

A group of proteins in circulation ready to destroy foreign cells, produced in the liver.

How many different types of proteins are in the complement system?

Over 30 different types of proteins.

What is the role of inflammation in the immune response?

Inflammation signals lead white blood cells (WBCs) to the site of infection (chemotaxis).

What is opsonization?

The process of labeling material as targets for phagocytosis.

What do membrane attack complexes do?

They form large holes in foreign cell walls to kill by lysis.

What triggers the inflammatory response?

Tissue damage leads to the release of histamines and cytokines, recruiting WBCs.

What are the main differences between innate and adaptive immunity?

Innate immunity is constantly present and general; adaptive immunity is variably present and specific.

What are dendritic cells?

Professional antigen-presenting phagocytes that connect the innate immune system to the adaptive immune system.

What is the humoral response?

The defense against circulating pathogens mediated by B cells.

What is the cell-mediated response?

The defense against compromised cells of the body mediated by T cells.

What is the role of memory T cells?

They retain immunity against specific pathogens.

What is the function of cytotoxic T cells?

They destroy infected self-cells presenting pathogens on MHC-I.

What are antibodies?

Y-shaped proteins used to identify foreign material; they can be attached to B cells or released into blood plasma.

What are the two types of chains in an antibody?

Heavy chain and light chain.

What is the significance of variable regions on antibodies?

They bind antigens, allowing the immune system to target specific pathogens.

How do B cells become activated?

When an antibody on a B cell binds to its specific antigen, requiring helper T cells for full activation.

What are the two sub-types of B cell clones after activation?

Memory cells and plasma cells.

What do plasma cells do?

They rapidly produce and release specific antibodies.

What is active immunity?

Adaptive immunity gained from your own immune system discovering and protecting against a pathogen.

What is passive immunity?

Adaptive immunity gained from someone else's immune system discovering and protecting against a pathogen.

What is the difference between natural and artificial active immunity?

Natural active immunity comes from infection, while artificial active immunity comes from vaccination.

What is natural passive immunity?

Maternal antibodies passed through the placenta.

What is artificial passive immunity?

Monoclonal antibody treatment.