Anatomy & Physiology (Immune System)

Pathogens

Potentially harmful foreign invaders that cause disease.

Five types of pathogens

Bacteria, viruses, fungi, protozoa, and helminths.

Microorganisms

The group of pathogens containing bacteria, viruses, and fungi.

Parasites

The group of pathogens containing protozoa and helminths.

Pathogenesis

The process through which pathogens cause disease.

Two main defense strategies

Preventing pathogens from entering and destroying those that do.

Autoimmune disease

An immune response triggered against the body's own healthy tissues.

Three levels of defense

The first two are nonspecific (innate); the third is specific (adaptive).

Nonspecific immunity

Innate defense mechanisms that protect against all kinds of pathogens.

Specific immunity

Adaptive or acquired defense that identifies and targets specific pathogens.

First line of defense

Physical and chemical barriers preventing external pathogens from entering.

Skin barrier

A physical barrier of dead cells with oily, acidic secretions.

Sebum

Unsaturated fatty acids providing a protective film that inhibits growth.

Lysozyme

An antimicrobial protein in secretions that breaks down bacterial cell walls.

Vibrissae

Nose hair that filters microbes, dust, and pollutants.

Cilia in lungs

Hair-like structures that trap and sweep foreign substances toward the throat.

Gastric juice

A highly acidic stomach secretion that kills microbes.

Symbiotic bacteria

Beneficial microbes in the gut and vagina that out-compete pathogens.

Urine

A fluid that physically flushes microbes from the urethra.

Expulsion mechanisms

Defecation and vomiting, which physically expel microorganisms.

Second line of defense

Nonspecific internal mechanisms targeting pathogens that entered the body.

Phagocytes

White blood cells that engulf pathogens using pseudopods.

Leukocytes

The general term for white blood cells.

Phagocytosis

The process of engulfing pathogens by extending pseudopods.

Hematopoiesis

The process of forming all blood cells in bone marrow.

Helminths

Parasitic worms that act as pathogens.

Sweat and sebum acidity

Chemical secretions on skin that inhibit bacterial growth.

Adaptive immune memory

Reduces the likelihood of sickness from previously-encountered pathogens.

Pseudopods

Extensions used by phagocytes to surround and engulf pathogens.

Monocytes

Circulating blood cells that mature into larger, long-living macrophages.

Macrophages

Mature monocytes that remove dead cells, debris, and pathogens.

Macrophage movement

They travel throughout the blood, lymph, and body tissues.

Macrophage role in inflammation

They play an important role in chronic inflammation.

Neutrophils

The most abundant type of white blood cell.

Neutrophil primary target

They primarily phagocytize bacteria during acute inflammation.

Neutrophil response time

They respond within minutes to the site of injury.

Mast Cells

Cells that secrete histamine and serotonin to cause inflammation.

Dendritic Cells

Messengers between the innate and adaptive immune systems.

Dendritic cell function

Acquire and present antigens to lymphocytes to activate them.

Dendritic cell origin

They can differentiate from monocytes, similar to macrophages.

Non-phagocytic white blood cells

Basophils and eosinophils.

Basophils

White blood cells that secrete chemicals such as histamine.

Histamine function

Triggers vasodilation to bring more phagocytes to an area.

Histamine symptoms

Responsible for the symptoms of allergies and the common cold.

Eosinophils

Short-lived cells that attack parasites and aid allergic responses.

Eosinophil proteins

Can be harmful to both pathogens and the body's own tissues.

Natural Killer (NK) Cells

Cells that attack abnormal or infected cells, like tumors.

NK cell mechanism

They release toxic granules to kill target cells.

Complement System

A group of about 30 proteins assisting defense reactions.

Complement System functions

Enhances phagocytosis, attracts phagocytes, and promotes cell lysis.

Complement protein synthesis

Generally synthesized by the liver.

Interferons

Proteins secreted by virus-invaded cells to warn neighboring cells.

Chemokines

Cytokines that guide cell movement along a chemical gradient.

Pyrogens

Substances that induce fevers.

Fever benefits

Inhibits bacterial growth and increases tissue repair rates.

Inflammatory Response

Biological response to harmful stimuli like infection or injury.

Five signs of inflammation

Swelling, pain, redness, warmth, and organ dysfunction.

Latin terms for inflammation signs

Tumor, dolor, rubor, calor, and functio laesa.

Chemokines

Chemical signals released by damaged cells to initiate the inflammatory response.

Mast cells

Cells that release histamine when stimulated by chemokines, bacteria, or direct damage.

Histamine

A chemical that causes capillary endothelial cells to enlarge and increases vessel porosity.

Vasodilation

The widening and increased porosity of blood vessels during inflammation.

Symptoms of vasodilation

Redness, increased temperature, and swelling in the affected tissue.

Metabolic effect of vasodilation

Increased local temperature, which raises the metabolic rate of nearby cells.

Selectins

Adhesion molecules displayed on the inner surface of activated capillary endothelial cells.

Neutrophil margination

The process where neutrophils are slowed down and roll along selectins on capillary walls.

Integrins

Adhesion receptors on neutrophils activated by chemicals in the bloodstream.

Margination (pavementing)

The accumulation and adhesion of leukocytes to blood vessel walls.

Diapedesis

The squeezing of leukocytes through openings in the capillary walls.

Alternative terms for diapedesis

Extravasation or emigration.

Exudation

The passage of plasma fluid, proteins, and antibodies from blood into interstitial fluid.

Edema

Fluid buildup in tissues due to exudation, visible as swelling (tumor).

Kinin system

A plasma-activated system generating proteins that sustain physical inflammation, like vasodilation.

Coagulation system

A plasma-activated system responsible for clotting at the site of injury.

Fibrinolysis system

A plasma-activated system that counter-balances the coagulation (clotting) effect.

Complement function in phagocytosis

Helps phagocytes engulf foreign cells and stimulates basophils to secrete histamine.

Basophils

Leukocytes stimulated by the complement system to secrete additional histamine.

Biochemical cascade

A signaling pathway where reactions to stimuli trigger a series of subsequent reactions.

Immune response

The specific third line of defense that targets particular foreign antigens.

Antigen

A foreign molecule, usually a protein or polysaccharide, identified as non-self.

Examples of antigens

Toxins, viral protein coats, or unique molecules on bacteria, protozoa, and pollen.

Major Histocompatibility Complex (MHC)

Glycoproteins on cell membranes used by the immune system to distinguish self from non-self.

Epitopes

Molecular protein fragments from inside a cell displayed on MHC molecules.

MHC uniqueness

Highly unique to each individual, except in cases like identical twins.

T-cell and MHC interaction

T-cells read MHC-displayed epitopes to check cells for foreign invaders.

Active MHC classes in immunity

Only MHC Class I and MHC Class II.

Number of MHC classes

There are three classes of MHC in total.

Erythrocytes and MHC Class I

Erythrocytes are the only cells in the body that do not display MHC Class I.

MHC Class I Display

All nucleated cells in the body display MHC Class I protein fragments.

Cytotoxic T-cell CD8 Receptor

Cytotoxic T-cells dock their CD8 receptors to MHC Class I molecules.

Cytotoxic T-cell Activation Trigger

If T-cell receptors fit the MHC Class I epitope, the T-cell triggers apoptosis.

Apoptosis

Programmed cell death triggered by cytotoxic T-cells in infected cells.

Cytotoxic T-cells in Adaptive Immunity

They play a role because their receptor shapes vary for each unique antigen.

MHC Class II Presenters

Displayed typically by antigen-presenting cells (APCs) like B-cells, macrophages, and dendritic cells.

Antigen-Presenting Cells (APCs)

Cells (B-cells, macrophages, dendritic cells) that consume antigens and display their epitopes.

Helper T-cell CD4 Receptor

Helper T-cells dock their CD4 receptors to MHC Class II molecules.

Naive Helper T-cell

A helper T-cell that has not yet been exposed to any antigens.

Naive Helper T-cell Activation

Occurs when its receptors bind to an MHC Class II epitope and learn to recognize it.

Helper T-cell Response to Activation

The activated helper T-cell starts secreting cytokines and multiplying itself.

Cytokine Function

Chemical signals that tell nearby B-cells and cytotoxic T-cells to target a specific antigen.