Immunity and Defense Mechanisms: Key Concepts in Human Biology

Immunity

The ability of an organism to resist infection.

Innate immunity

Rapid, present at birth. Non-specific, first and second lines of defense.

Adaptive immunity

Slow response. Memory component. Highly specific-targeted, third line of defense.

First line of defense

Innate: Skin and Mucosal Membranes | Physical Factors | Chemical Factors.

Prebiotics

Chemicals (nutrients) that support the growth of beneficial microorganisms.

Probiotics

Live microbial cultures that provide health benefits.

Second Line of Defense

Innate: Commonly associated with inflammation and fever.

Inflammation

Local or systemic defensive response triggered by damage to tissues.

Signs and symptoms of inflammation

Pain, redness, immobility, swelling (edema), heat.

Acute inflammation

Develops rapidly, lasts for few days to few weeks.

Chronic inflammation

Develops more slowly, lasts months to years; may be severe and progressive.

Neutrophils

Highly phagocytic; most active in early stages of infection; first responders.

Histiocytes

Fixed macrophages that are residents in tissues and organs.

Free (wandering) macrophages

Roam tissues and gather at sites of infection, clean-up crew.

Natural Killer (NK) Cells

Kill infected cells by releasing perforin, causing membrane to perforate and rupture.

Leukopenia

Low white blood cell count. Lowered immune system.

Leukocytosis

High white blood cell count. Overactive immune system.

Cytokines

Signaling proteins regulating immunity and inflammation.

Fever

Abnormally high body temperature (38C or higher, 100.4F or higher).

Complications of Fever

Tachycardia, acidosis, dehydration, seizures, coma.

Interferons

Released by host cells in response to the presence of several viruses.

Antigens

Substances that cause the production of antibodies.

Antibodies

Own immune cells make them.

Primary response

First time the immune system combats a particular foreign substance.

Secondary response

Later interactions are faster and more effective due to 'memory'.

Humoral immunity

Addresses threats outside of the cell.

B cells

Lymphocytes created and mature in red bone marrow. Recognize antigens and make antibodies.

Plasmacytes

Activated B cells that produce antibodies.

Memory cells

Store information for future infections.

Cellular immunity

Targets infected cells (inside of cell).

Cytotoxic T cells

Target and kill infected cells as well as destroy tumor cells, activated by antigens.

Helper T cells

Signal other cells to attack pathogen, most important T cell.

Suppressor T cells

Regulate and reduce activity of other T cells as needed.

Immunoglobulins

IgM associated with primary humoral immune response.

IgG

Higher in secondary immune response, easier to produce.

Natural adaptive immunity

Active - Experienced the disease and produced associated antibiotics and memory cells.

Passive immunity

Passed from mother to fetus, transferred in last 3 months, temporary.

Artificially Acquired Immunity

Active - Immunization or vaccination.

Passive artificial immunity

Injection of antibodies generated by a different person or animal.

Allergies

Histamines cause inflammatory response.

Autoimmune disease

Body attacks itself.

Severe combined immunodeficiency (SCID)

Absence of T and B cell function, Genetic (Born with).

Acquired immunodeficiency syndrome (AIDS)

Caused by HIV, Similar to SCID, Targets white blood cells.

Virulence

The degree of pathogenicity.

Infection

Invasion or colonization of the body by pathogens.

Disease

An abnormal state in which the body is not performing normal functions.

Koch's postulates

Used to prove the cause of an infectious disease.

Communicable disease

A disease that can spread from one host to another.

Contagious diseases

Diseases that are easily spread from one host to another.

Vesicles

Fluid-filled lesions.

Bullae

Vesicles larger than 1 centimeter.

Macules

Flat, reddened lesions.

Papules

Raised lesions.

Pustules

Raised lesions with pus.

Impetigo

Red sores around nose and mouth that break open and leave crust.

Folliculitis

Infections of the hair follicles.

Sty

Folliculitis of an eyelash.

Furuncle (boil)

Type abscess; localized region of pus surrounded by inflamed tissue.

Carbuncle

Damage and inflammation of deep tissue from spreading furuncle, clusters.

Scalded skin syndrome

Fever, irritation, large sheets of skin affected.

Toxic shock syndrome (TSS)

Caused by S. aureus; fever, vomiting, shock, and organ failure.

Staphylococcus Epidermidis

Part of normal skin microbiota. Produces biofilm on catheters.

Staphylococcus Aureus

Carried in the nasal passages. Produces damaging toxins and causes Sepsis.

MRSA

Methicillin-resistant Staphylococcus aureus; spread through direct contact.

Group A streptococci (GAS)

Streptococcus pyogenes; causes strep throat, cellulitis, impetigo.

Necrotizing Fasciitis

Flesh-eating disease caused by exotoxin A produced by S. pyogenes.

Pseudomonas aeruginosa

Gram-negative, aerobic rod; produces exo- and endotoxins.

Buruli Ulcer

Caused by Mycobacterium Ulcerans; enters via a break in the skin.

Acne

Skin cells shed in hair follicles and combine with sebum, causing blockages.

Warts

Caused by papillomavirus, transmitted via contact.

Smallpox

Caused by an orthropoxvirus; completely eradicated by vaccination.

Chickenpox (Varicella)

Caused by herpesvirus varicella-zoster; prevented by a live vaccine.

Shingles

Reactivation of latent varicella-zoster virus due to stress or lowered immunity.

Herpes Simplex

Caused by HSV-1 and HSV-2; remains latent and usually develops as cold sores.

Measles/Rubella

Viral disease transmitted by respiratory route; prevented by MMR Vaccine.

Congenital Rubella Syndrome

Causes fetal damage/mortality; can be prevented by the MMR vaccine.

Cutaneous mycoses

Caused by dermatophytes

Ringworm

Circular rash caused by fungal infection

Athletes foot

Fungal infection that causes an itchy, stinging, burning rash on your skin of your feet

Subcutaneous Mycoses

Usually caused by fungi that inhabit the soil

Sporotrichosis

Caused by Sporothrix schenkii; dimorphic fungus, enters a wound, and forms a small ulcer

Candidiasis

Overgrowth of Candida albicans. Occurs in skin and mucous membranes of genitourinary tract and mouth

Thrush

Candida Albicans infection of the oral cavity. When antibiotics suppress competing bacteria

Scabies

Caused by Mites, burrow in the skin to and lay eggs

Pediculosis (Lice)

Feed on blood from the host, lay eggs (nits) on the hair and attach to the shafts

Conjunctivitis

An inflammation of the conjunctiva, commonly caused by Haemophilus influenzae bacterium

Ophthalmia Neonatorum

Caused by Neisseria gonorrhoeae. Untreated cases may lead to blindness

Inclusion Conjunctivitis

Caused by Chlamydia Trachomatis. Spread through swimming pool water

Trachoma

Caused by some types of Chlamydia Trachomatis. Leading cause of blindness worldwide

Sepsis

Body's excessive reaction to infection leading to full body inflammation

Keratitis

Infection of the cornea from contaminated contact lenses

Bacterial Meningitis

Initial symptoms of fever, headache, and a stiff neck, may progress to convulsions and coma

Neisseria Meningitidis Meningitis

Begins as a throat infection, rash, and bacteremia. Outbreaks common in dorms and military barracks

Streptococcus Pneumoniae Meningitis

Infection of the brain and spinal cord. Healthy nasopharyngeal carriers cause pneumonia and otitis media

Listeriosis

Caused by Listeria monocytogenes. Usually foodborne and asymptomatic meningitis more common in the immunocompromised

Tetanus

Caused by Clostridium tetani. Tetanospasmin neurotoxin released from dead cells

Botulism

Caused by Clostridium botulinum. Intoxication comes from ingesting the botulinum exotoxin

Poliomyelitis

Caused by the poliovirus. Transmitted by the ingestion of water containing feces containing the virus

Rabies

Caused by the rabies virus, genus Lyssavirus. Usually transmitted by the saliva of animal bite

Rheumatic fever

Inflammation of the heart valves. Autoimmune complication of S.pyogenes infections