Immune System Part One: Non-specific Defence

Pathology

the scientific study of the causes, mechanisms, and effects of disease

Immunology

the scientific study of the immune system and how the body protects itself against infection, disease, and foreign invaders

Normal flora

Microorganisms that normally live on or inside the body without causing harm and may provide benefits.

Symbiosis

A close relationship between two different species living together.

Mutualism

A symbiotic relationship where both organisms benefit.

Commensalism

A relationship where one organism benefits and the other is neither helped nor harmed.

Opportunistic pathogens

Microorganisms that normally do not cause disease but can cause illness when the host’s defenses are weakened.

Local Infection

An infection confined to one specific area of the body.

Systemic Infection

An infection that spreads throughout the body, often through the blood or lymphatic system.

Primary Infection

The initial infection caused by a pathogen in the body.

Secondary Infection

An additional infection that develops during or after a primary infection, often because the body's defences are weakened.

Non-specific defense systems

Body defenses that protect against a wide range of pathogens without targeting a specific one; part of innate immunity.

Avoidance

The host prevents exposure to pathogens through behaviours or barriers, such as avoiding contaminated food.

Resistance

The host prevents pathogens from entering, establishing themselves, or multiplying in the body.

Effector mechanisms (mediators)

The host uses immune responses to eliminate pathogens or limit their harmful effects.

Tolerance

The host limits damage caused by a pathogen without necessarily eliminating it.

Sensor cells

Cells that detect pathogens or tissue damage and trigger an immune response.

Macrophages

is to destroy microbial/microscopic threats via phagocytosis, trigger inflammation, and attract other immune system cells to help repel threat

Dendritic cells

is to engulf the pathogen and carry molecular pieces (antigenic material) of the pathogen to cells of the specific immune system (so they need to move)

Mast cells

is primarily to trigger inflammation and activate the circulatory system to more effectively fight infectious threat (they mainly stay stationary)

DAMPs

Damage Associated Molecular Patterns

Neutrophils

• White blood cells that rapidly respond to infections by engulfing and destroying pathogens, especially bacteria.

• move in and out of the blood stream and will migrate to the location of infections
  (they are not normally found in healthy tissues).

Monocytes

circulate in the blood, typically for a few days (depending on specific type). When an injury or infection occurs, monocyte production is increased.

Natural killer cells (NK)

a type of lymphocyte that are produced by the same stem cells that produce the T and B
cells of the specific immune system (more later).

Chemotaxis

The movement of cells toward chemical signals, guiding immune cells to sites of infection or inflammation.

Adherence

The process by which immune cells attach to pathogens or infected tissues so they can destroy them.

Cytolysis

The destruction of a cell by breaking its cell membrane, causing its contents to leak out.

Inflammation

The body's response to injury or infection, bringing immune cells and chemicals to the affected area to fight pathogens and begin healing.

Cytokines

Signaling proteins released by cells that coordinate immune responses and regulate inflammation.

Histamine

A chemical released by immune cells that widens blood vessels and increases their permeability during inflammation.