Immune System Flashcards
Pathogens
■ Microscopic organisms that cause disease:
o viruses
o bacteria
o fungi
o parasites
■ nEach attacks in a specific way
Body defenses
■ Provide resistance to fight infection, illness, and disease
■ 2 categories of defenses:
■ nonspecific (innate) defenses
■ specific (adaptive) defenses
Nonspecific defenses
■ Always work the same way
■ Against any type of pathogen agent
7 types of nonspecific resistance
- Physical barriers
- Phagocytic cells
- Immunological surveillance
- Interferons
- Complement
- Inflammation
- Fever
Specific defenses
■ Protect against specific pathogens
■ Depend on activities of lymphocytes
■ Specific resistance (immunity):
■ develops after exposure to environmental hazards
Nonspecific and specific defenses
Operate together to provide resistance to infection and disease
7 nonspecific defenses: physical barriers
■ Keep hazardous materials outside the body
■ Outer layer of skin
■ Hair
■ Epithelial layers of internal
passageways – Mucous Membranes
■ Secretions that flush away materials:
■ sweat glands, mucus, and urine
■ Secretions that kill or inhibit microorganisms:
■ enzymes, antibodies, acidity of skin and stomach acid
■ Respiratory system modifications
■ Mucus-coated hairs in nose
■ Cilia of upper respiratory tract sweep dust- and bacteria-laden mucus toward mouth
■ Surface barriers breached by nicks or cuts - second line of defense must protect deeper tissues
Phagocytes
■ Attack and remove dangerous microorganisms
■ First line of cellular defense
2classes of phagocytes
■ Microphages:
■ neutrophils and eosinophils
■ Macrophages:
■ large phagocytic cells derived from monocytes
2 types of macrophages
■ Fixed macrophages
■ Free (wandering) macrophages
Fixed macrophages
■ Also called histiocytes
■ Stay in specific tissues or organs:
■ e.g., dermis and bone marrow
Specific Histiocytes
■ Microglia:
■ found in central nervous system
■ Kupffer cells:
■ found in liver sinusoids
Free (wandering) macrophages
■ Travel through blood stream
■ Special free macrophages:
■ alveolar macrophages (phagocytic dust cells)
3 functional characteristics of free macrophages and mircophages
■ Emigration – the ability to move through capillary walls
■ Chemotaxis – They are attracted or repelled by chemicals in surrounding fluids
■ Cytokines
■ Adhesion - phagocytosis begins:
■ when phagocyte attaches to target adhesion
■ Some microorganisms evade adherence with capsule
NK cell function
■ Identifies and attaches to abnormal cell (non-selective)
■ without the “self” cell surface protein markers
■ Antibody coating target cell
■ or with abnormal markers
■ Induce apoptosis in cancer cells, foreign and virus-infected cells
■ Secrete potent chemicals that enhance inflammatory response
Interferons
■ Proteins (cytokines) released by activated lymphocytes, macrophages and virus-infected cells
Cytokines
■ Chemical messengers released by tissue cells:
■ to coordinate local activities
■ Can trigger production of antiviral proteins in surrounding normal cells
■ Antiviral proteins:
■ do not kill viruses
■ block replication in cell
3types of interferons
■ Alpha and Beta interferons:
■ produced by leukocytes
■ Also attract and stimulate NK cells
■ Gamma interferons:
■ secreted by T cells and NK cells
■ Widespread immune mobilizing effects
■ stimulate macrophage activity
■ Since IFNs activate NK cells and macrophages, indirectly fight cancer
■ Artificial IFNs used to treat hepatitis C, genital warts, multiple sclerosis, hairy cell leukemia
Complement
■ Plasma contains ~ 20 complement (C) proteins:
■ that complement antibody action
■ Include C1–C9, factors B, D, and P, and regulatory proteins
■ Major mechanism for destroying foreign substances
■ Our cells contain complement activation inhibitors
Complement (C) proteins
■ Form the complement system
■ Complements action of antibodies
Complement activation
■ Enhances both innate and adaptive defense
■ 3 pathways activate the complement system
■ classical pathway
■ alternative pathway
■ Lectin pathwa
Classical pathway
■ Fast method
■ C1 binds to or is fixed to antibody molecule attached to antigen (bacterium)
■ Bound (fixed) protein acts as enzyme:
■ catalyzes chemical reaction between other C proteins
Alternative pathway
■ Slow method (No antibody involved)
■ Involves the exposure to antigen on the surface of a microbe :
■ factor P (properdin)
■ factor B
■ and factor D interact in plasma
Lectin pathway
■ Slow method (also no antibody involved)
■ After digesting microbes, macrophages release substances that:
■ Cause the liver to produce lectins
■ Lectins bind to microbes causing the activation of C3
Complement Activation
■ All 3 pathways end with:
■ conversion of inactive complement protein (C3)
■ to active form (C3a + C3b)
4 effects of complement activation
- Stimulation of inflammation - stimulates histamine release
- Promoting chemotaxis - Attraction of phagocytes to areas of pathogen through chemical signals
-increases the number of leukocytes in a tissue - Opsonization
▪ Enhancement of phagocytosis by :
■ complements working with antibodies (opsonins) to coat pathogens and make it easier for macrophages to bind - Destruction of target cell pathogens (lysis):
■ 5 complement proteins join to form membrane attack complex (MAC)
Inflammation
■ Also called inflammatory response
■ A biological response
■ Triggered by any stimulus that kills cells or injures tissue
■ Begins with chemicals released into ECF by injured tissues, immune cells, blood proteins
■ Macrophages and epithelial cells of boundary tissues bear Toll-like receptors (TLRs)
■ 11 types of TLRs recognize specific classes of infecting microbes
■ Activated TLRs trigger release of cytokines that promote inflammation
Cardinal signs and symptoms of inflammation
■ Swelling (tumor)
■ Redness (rubor)
■ Heat (calor)
■ Pain (dolor)
4 Effects of inflammation
- Temporary repair and barrier against bacteria
- Retards spread of pathogens into surrounding areas
- Mobilization of local and systemic defenses:
■ and facilitation of repairs (regeneration) - Alerts adaptive immune system
Injured cells release:
■ prostaglandins
■ proteins
■ potassium ions
Products of inflammation
■ Necrosis:
■ local tissue destruction in area of injury
■ Pus:
■ mixture of debris and necrotic tissue
■ Abscess:
■ pus accumulated in an enclosed space
Fever
■ A high body temperature:
■ increases body metabolism
■ accelerates HR, respiratory function, protein use, immune function, and mental processing
■ inhibits some viruses and bacteria
■ Causes liver and spleen to sequester iron and zinc (needed by microorganisms)
■ A maintained body temperature above 37°C (99°F)
