Unit 4 - Immune System PART C-E Flashcards
List the Innate Immunity – Physical Barriers
- Skin
- Hairs in Nasal Passageway / Eyelashes
- Mucous Membranes
Innate Immunity – Physical Barriers
Skin:
- tough protective layer outer layer (cells are KERATINIZED)
- sweat from sweat glands contains BACTERIOCIDAL CHEMICALS
- SEBUM (oil) from sebaceous glands blocks pores and reduces cracking of skin
Innate Immunity – Physical Barriers
Hairs in Nasal Passageway / Eyelashes:
filter larger airborne particles
Innate Immunity – Physical Barriers
Mucous Membranes:
- lines all body cavities/tracts that open to the outside of the
body including the respiratory, gastrointestinal, urinary, and
reproductive, tracts. - mucus produced by Goblet cells in mucus membranes traps pathogens and other particles
Innate Immunity – Mechanical Barriers
Involves flushing mechanisms (cilia that move creating fluid flow)
Innate Immunity – Mechanical Barriers
Examples:
- Mucociliary escalator
- Flow of tears
- Flow of urine
- Coughing and Sneezing
Innate Immunity – Mechanical Barriers
Mucociliary escalator:
- Involves the mucus membrane of the respiratory tract which is composed of a ciliated pseudostratified epithelium. The mucus produced by the goblet cells in this membrane traps microbes/debris.
- The beating (movement) of the cilia lining the bronchi and trachea then pushes the mucus along with its trapped microbes/debris from the lungs towards the pharynx (throat).
Innate Immunity – Mechanical Barriers
Flow of tears:
Tears produced by the lachrymal gland flow over the surface of the eye diagonally, removing microbes and debris.
Innate Immunity – Mechanical Barriers
Flow of urine:
Removes microbes and debris from the urinary tract.
Innate Immunity – Mechanical Barriers
Coughing and Sneezing:
Blows out irritants (at speeds ≥ 160 km per hour)
Innate Immunity – Chemical Barriers
- pH
- Enzymes
- Antibodies
- Complement System
- Interferons (& innate defense against viruses)
Innate Immunity – Chemical Barriers
pH:
acidity creates inhospitable environment for microbes
a. Skin
b. Stomach
c. Mucous Membranes
Innate Immunity – Chemical Barriers
pH in SKIN:
Skin = pH 4.5 – 6 (referred to as the “acid mantle”)
Innate Immunity – Chemical Barriers
pH in STOMACH:
Stomach = hydrochloric acid, pH = 1 – 2
Innate Immunity – Chemical Barriers
pH in MUCOUS MEMBRANE:
Mucous Membranes = e.g. nasal cavity mucus has pH of 5.5-6.5
Innate Immunity – Chemical Barriers
Enzymes:
damage microbes (especially bacteria)
a. Lysozyme
b. Proteases
Innate Immunity – Chemical Barriers
Enzymes
Lysozyme:
damage bacterial cells walls of unencapsulated bacteria.
Found in many body fluids including tears, sweat, saliva, intestinal and bronchial mucus, breast milk).
Innate Immunity – Chemical Barriers
Enzymes
Proteases:
(e..g. pepsin = digestive enzymes associated with
gastrointestinal tract) – antibacterial activity.
Innate Immunity – Chemical Barriers
Antibodies
gA (Immunoglobulin A) antibodies:
bind to pathogens, clump them together and mark them for phagocytosis in case they cross into the internal environment.
Found in many body fluids including tears, sweat, saliva, intestinal and bronchial mucus, breast milk.
Physical, mechanical & chemical barriers
- Epithelium
- Glandular Secretions
- Stomach Acidity
- Mechanical Removal
Epithelium
the protective barrier of skin & mucous membranes is the body’s 1st line of defense
Glandular Secretions
secretions include: - mucous - antibodies - enzymes to trap & disable pathogens
Stomach Acidity
the low pH of the stomach helps destroy swallowed pathogens
Mechanical Removal
pathogens can be physically removed
- mucociliary escalator
- tears
- coughing, sneezing
- GI motility
Innate Immunity – Chemical Barriers
Complement System:
Part of initial response to bacterial invasion.
Cascade of over 30 proteins (found in extracellular fluids) that results in phagocytosis or lysis of foreign cells.
- the complement proteins are secreted in inactive forms that are activated as the cascade proceeds
- the cascade ends with the formation of MEMBRANE ATTACK COMPLEX, a group of lipid proteins that insert themselves into the cell membrane of pathogens & virus-infected cells & form giant pores (allow water & ions to enter the pathogen cells)
- result: cells swell & lyse
The most important protein of the complement system is…
complement protein C3 and specifically the C3b portion of this protein.
Other functions of the complement system include:
a. Activation of inflammation via mast cells
b. Opsonization (marking/flagging) of bacteria (via C3b).
c. Complement proteins acting as chemotaxins
(chemicals that attract cells) which helps to direct
phagocytes towards invading pathogens like bacterial
cells.
Opsonins
are molecules that coat foreign particles to make them visible “food” for phagocytic leukocytes
Some cytokines act as _____ that raise body temp by altering the hypothalamic set-poit
pyrogens
Chemotaxins
chemicals that attract cells
- (signal molecules that attract leukocytes to help fight the infection)
Describe the 3 steps in the immune responses to extracellular bacteria
- bacterial infections cause inflammation & trigger immune responses
- ACTIVATION OF THE COMPLEMENT SYSTEM
- formation of membrane attack complex
- activation of mast cells, with production of chemotaxins & histamine
- complement proteins act as opsonins to enhance phagocytosis - ACTIVITY OF PHAGOCYTES
- complement, antibodies, & other proteins act as opsonins to enhance phagocytosis - ADAPTIVE IMMUNE RESPONSE
- antigen-presenting cells stimulate other lymphoid cells to produce antibodies & cytokines
Innate Immunity – Chemical Barriers
Complement Activation:
a. Classical Pathway
b. Alternative Pathway
Fig 24.6
Innate Immunity – Chemical Barriers
Complement Activation:
a. Classical Pathway
(requires that adaptive immune response has occurred)
C1 complement proteins are activated by binding to antibodies (IgG, IgM) that are already bound to pathogen (e.g. bacteria).
Cascade produces C3 and C3b.
Innate Immunity – Chemical Barriers
Complement Activation:
b. Alternative Pathway
(completely innate)
- Carbohydrates on pathogen surface directly activate formation of C3 and C3b.
Innate Immunity – Chemical Barriers
Complement Activation:
c. Result of both pathways:
i. C3b acts as opsonin that flags/marks pathogens for PHAGOCYTOSIS (phagocytes have C3b receptors)
ii. C3b helps to form MEMBRANE ATTACK COMPLEXES (MAC)
- Is converted to C5b, which punctures holes (pores) in microbe cell membranes, allowing Na+ and water to enter the cell – result = LYSIS (rupture of cell membrane
iii. Byproducts C3a and C5a activate leukocytes involved in inflammatory response (mast cells, basophils)
Membrane Attack Complexes (MAC)
Is converted to C5b, which PUNCTURES holes (pores) in microbe cell membranes, allowing Na+ and water to enter the cell – result = LYSIS (rupture of cell membrane)
Innate Immunity – Chemical Barriers
Interferons (& innate defense against viruses):
Interferons play an important role in short term innate immune defense against viruses.
Also reinforces other immune activities:
1) enhances macrophage phagocytic activity;
2) stimulates antibody production;
3) enhances action of Natural Killer Cells.
Innate Immunity – Chemical Barriers
Interferons (& innate defense against viruses) also reinforce other immune activities:
1) enhances macrophage phagocytic activity;
2) stimulates antibody production;
3) enhances action of Natural Killer Cells.
Innate Immunity – Chemical Barriers
Interferons (& innate defense against viruses)
Mechanism of Interferon action:
a. Viral RNA enters cell (e.g. COVID-19, Influenza, West Nile Virus, etc.)
b. Virus uses host cell for replication.
c. Virus causes host cell to produce Interferon α & β
d. Interferon α & β are released from infected host cell and bind to cell membrane receptors on healthy neighboring cells. Triggers production of antiviral proteins (AVPs) in healthy cells.
e. When virus tries to infect cells with AVPs, viral replication is blocked.
