THE IMMUNE SYSTEM

Immune system

protects the body by defending against disease causing pathogens, identifying and destroying abnormal or cancerous cells

Pathogens

A disease-causing agent that enters the body

viruses, bacteria and fungi

Antigen

A molecule recognized by the immune system as foreign

often found on the surface of a pathogen

triggers immune response including antibody production

First line of defense

Physical barriers

outside of the body: skin

Inside of the body: mucous membranes

Second line of defense

Innate immune system

Innate immune cells

first responders after injury/infection

initiate acute and rapid (minutes-hours) inflammatory response

Inflammation

destroys pathogens and assist healing of damaged tissues

Phagocytes

destroy foreign cells by “eating” them and signal other immune cells

monocytes/macrophages

neutrophils

dendritic cells

Natural killer (NK) cells

cells kill cells compromised by pathogen/tumor

Third line of defense

Adaptive immune system

Adaptive immune system

involved in protection against viruses

only present in about 1% of organisms including humans

takes days to mobilize

comprised of a type of leukocyte called a lymphocyte

B cells (B-lymphocyte)

produce antibodies that the immune system “remembers”

T-cells (T-lymphocytes)

helps when the invader is inside a cell

killer (cytotoxic) T cells, helper T cells, memory T cells, regulatory T cells

Humoral vs cellular immunity

present in both: innate and adaptive immune systems can be divided into humoral components and cellular components

Humoral immunity

processes occuring outside of cells

cellular immunity

processes occurring inside of cells

Cytokines

small signaling proteins released by immune cells and other cells in the body

bind to receptors on nearby cells and change how those cells behave

immune system chemical messengers

Cytokines help

activate and direct immune cells

recruit leukocytes to an infection or injury

initiate, maintain, or reduce inflammation

coordinate healing and recovery

pro-inflammatory cytokines

increase immune activity and inflammation

anti-inflammatory cytokines

limit inflammation and help restore balance

Cytokine activity

you can feel cytokine activity

short term cytokine activity can produce “sickness behavior”

research suggests that individuals can detect their levels of pro-inflammatory cytokines through interoception

feelings of general malaise and chronic fatigue

Adaptive

conserve energy for recovery

chronic illnesses involving the immune system

AIDS

many cancers

autoimmune disorders

chronically elevated inflammation