Overview of the Immune System and Its Defenses

Innate Immunity

It works right away to protect the body, attacks anything harmful without focusing on one specific kind, involves skin, white blood cells (neutrophils), and proteins (complement system), and does not remember past infections.

Adaptive Immunity

It takes time to activate, targets specific threats, involves B cells and T cells, remembers infections, and responds faster and stronger to the same threat.

Normal Microbiota

Help protect the body by taking up space and nutrients, making it harder for harmful germs to grow, training the immune system to fight infections, and controlling inflammation.

First-Line Defenses

To stop harmful germs from getting into the body and causing infection.

Mechanical Barriers

Block or push out germs, including skin, mucus and tiny hairs in the nose and throat, and tears and saliva.

Chemical Barriers

Use substances to kill or stop germs, including stomach acid, enzymes in tears and saliva, and sweat and body oils.

Physical Barriers

Act as a shield against germs, including skin, mucous membranes, and the blood-brain barrier.

Neutrophils

Common white blood cells that are the body's first line of defense against infection, moving quickly to sites of infection to help fight bacteria and fungi.

Eosinophils

Have large, red-orange granules and a two-lobed nucleus, fight parasitic infections, help with allergic reactions, and release enzymes and toxins to kill parasites.

Basophils

Least common white blood cells with a two-lobed nucleus and dark purple granules that release histamine to start inflammation and play a role in allergic reactions.

Mast Cells

Found in tissues instead of blood, have large granules, release histamine to start inflammation, help with allergic reactions, and are located near body openings.

Monocytes

White blood cells that can turn into macrophages and dendritic cells. Travels in blood

Macrophages

Big white blood cells that swallow and break down germs and dead cells.

Dendritic Cells

Antigen-presenting cells take in antigen material, process it, and show it on their surface for T cells to recognize.

Monocytes

travel in the blood and can change into macrophages or dendritic cells.

Macrophages

found in tissues, eat germs and dead cells and help alert other immune cells.

Dendritic cells

found in the skin and organs, capture germs and tell other immune cells to respond.

T-cells

help control the immune response and attack infected or non-normal cells. They also mature in the thymus.

B cells

make antibodies to fight off infections and mature in the bone marrow.

Natural Killer Cells

kill infected or cancer cells without needing antibodies and attack cells directly when they are stressed or infected.

Chemokines

signals that guide immune cells to the infection/injury site.

Interleukins

helps the immune system communicate with each other and control the growth and activity of different immune cells.

Interferons

Essential in protecting the body from viruses by warning nearby cells and making immune cells more active.

Goals of inflammation

1. Protect the body - fight off infections/injuries 2. Limit damage - prevent harm from spreading 3. Heal the body - repair the affected area.

Phases of inflammation

1. Vascular - blood vessels dilate and leak fluid to the injured area. 2. Cellular - white blood cells move to the injured area. 3. Resolution - inflammation goes down and tissue begins to heal.

Chronic inflammation

It may develop when the inflammatory response goes on too long, harming tissues and causing more damage.

Goals of fever

It boosts the body's defense against viruses, makes immune cells work better, increases the production of white blood cells, slows the growth of some harmful germs, and helps tissue repair faster.

FUO

A fever that lasts at least 3 weeks with no clear cause after one week of tests.

Intermittent fever

It is when the body temperature goes up but returns to a normal state at some point during the day.

Pel-Ebstein fever

Fever lasts 3-10 days, followed by a period without fever for the same amount of time.

Relapsing fever

fever comes and goes, with normal temperature in between, caused by certain bacteria spread by ticks.

Remittent fever

the temperature stays high and fluctuates but never goes back to normal.

Sustained fever

the temperature stays high and does not change much throughout the day.

Tertian fever

fever happens every 1st and 3rd day, usually seen in malaria caused by Plasmodium vivax.

Quartan fever

fever happens every 1st and 4th day, usually seen in malaria caused by Plasmodium malariae.