Immunology Flashcards
(33 cards)
What are some infectious agents to an animals environment?
- Viruses
- Bacteria
- Protozoa
- Parasites
- Fungi
- Prions
Health/Disease Triangle
Host-Agent-Environment
Intracellular Pathogens vs. Extracellular Pathogens
• All viruses, some bacteria and some protozoan parasites
replicate inside host cells
• Immune responses must recognize and destroy the infected
cell
• Many bacteria and larger parasites live in tissues, body fluids
or other extracellular spaces
• The immune system must differentiate between the two
• Intracellular pathogens exist as extracellular pathogens en
route to their target cell
Primary function of the immune system
• Eliminate infectious agents and minimize the
damage they cause.
external defenses in immune response
Effective against many organisms
• Skin, forms a thick multicellular barrier. Fatty acid secreted from
sebaceous glands keeps the skin PH between 5-5.5. This low PH is
bactericidal to certain bacteria.
routes of access
- GI epithelia
- Urogenital
- Nasopharynx
- Lung
- Direct blood contact
external defenses
• Lysozyme in tears and secretions dissolves and destroys the
cell wall of bacteria especially gram +
• Respiratory tract – cilia which lines the respiratory tract
removes foreign particles, mucous/secretions flush FB away.
• Skin – fatty acids, physical barrier commensal organisms
• Urinary Tract – flushing
• GI Tract – Commensal organisms, stomach acid, PH changes
internal defenses
- blood
- WBC
- Macrophages
- Neutrophils
- Eosinophils
- Basophils
- Lymphocytes
- Monocytes
- RBC
- spleen
- lymph
Innate Immunity (non-adaptive)
• Non-specific, most primitive
• Phagocytosis, consisting of the phagocytic cells of the reticuloendothelial
system (Macrophages); Neutrophils, Eosinophils, and Basophils
• Does not alter with repeated exposure
Adaptive immunity
- Specific, more sophisticated
- Includes Lymphocytes, their progeny and their extracellular products
- Improves with each successive exposure to the same pathogen (“Memory”)
innate immune response
White blood cells(Leukocytes) • Primarily responsible for eliciting and coordinating the immune response • Phagocytes • Monocytes, macrophages, polymorphonuclear neutrophils, eosinophils, basophils • Bind, internalize, kill microorganisms • Nonspecific=>Innate immune response
Phagocytes
• Innate immune response • Derived from bone marrow stem cells • Mononuclear phagocytes • Engulf particles including infectious agents and destroy them • Strategically placed (e.g. kupffer cells-liver) • Monocytes (blood) • Macrophages (tissue) • Act as Ag presenting cells • Polymorphonuclear neutrophils (PMN) •Majority of blood leukocytes •Migrate to tissues in response to certain stimuli • Engulf material, destroy it, and die.
lymphocytes
•Central to adaptive immune response
• Specifically recognize individual pathogens
• Two major categories
•B-lymphocytes(B-cells)
• T-lymphocytes(T-cells)
•Wholly responsible for specific immune recognition
of pathogens=> central to adaptive immune
response.
•All derived from bone marrow stem cells
• T-cells develop in Thymus
•B-cells develop in bone marrow (in adults)
•In the fetus the immune process begins in the yolk
sac, then fetal liver, bone marrow takes over close
to parturition.
B-lymphocytes
B-cells
• Combat extracellular pathogens and their
products(Antigen, Ag) by releasing Antibody (Ab)
•Originate in the bone marrow
•Migrate to and locate in the spleen and lymph
nodes throughout the body
•Genetically programmed to encode a surface
receptor specific for a particular Ag
•Undergo stimulation by Ag and increase rapidly in
numbers
•Differentiate into plasma cells which secrete Ab
T-lymphocytes
T-cells
• Control of B-cell development and Ab production
• Interact with phagocytic cells to help them kill
• Recognize cells infected with viruses
Produced in the bone marrow
• Undergo maturation process in the Thymus gland
• Migrate to lymph glands and enter circulation
• Constitute 40-60% of all circulating lymphocytes in blood.
• Secrete factors called cytokines
• Cytokines assist phagocytes and macrophages in destroying
pathogenic microorganisms
• Do not manufacture Ab
• T-cells sometimes called memory cells
• T-cell immunity=>Cell mediated immunity (CMI)
Several different types
• T-helper (TH) cells – two types
TH1-secrete Interleukin-2 (IL-2) and Interferon (INF).
These are important in the CMI response and killing of
intracellular pathogens (viruses, bacteria, parasites)
TH2 – secrete IL- 4,5,6,10. Important in antibody
mediated response (Humoral immunity) and free- living
organisms.
- T-cytotoxic (Tc) cells
- Destruction of host cells infected with viruses or other
intracellular pathogens
T-suppressor (Ts) cells – suppress immune responses
• T-cells recognize antigens in association with familiar
markers on host cells=T-cell receptor(TCR). Similar in
structure and function to B-cell antigen receptor site.
• T-cells generate their effects by releasing soluble proteins
called cytokines.
cytotoxic cells
a cell that can injure or kill other cells
•Recognize surface changes on tumor cells
and virally infected cells
•Use non-specific mechanisms
•Natural Killer activity or NK cells
•Eosinophils
•Engage and damage large extracellular
parasites
Cytotoxic Reactions
• Directed against whole cells too large for phagocytosis
• Cell recognition by TCR or Ab bound to cell surface
• Granules directed at target cells
• Perforins – create holes in target’s outer membrane
Apotosis
• Cytotoxic cells can signal target cells to undergo
programmed self-destruction
acute phase proteins
mediator of immunity
• Molecules normally present in serum
• Concentrations increase rapidly during infection
• Fibrinogen = acute phase protein; used in ruminants and
horses as in indicator of an acute inflammatory response
complement protein
Group of serum and cell surface proteins activated by
factors such as Ag/Ab combination resulting in enzyme
cascades that have a variety of biological consequences
such as cell lysis and opsonization.
• Alternate activation pathway
• Spontaneous
• Innate, nonspecific response
• Classical activation pathway
• Ab mediated activation
• Adaptive response
• Cascade reaction = compliment cascade
cytokines
soluble mediator of immunity Signaling molecules • Proteins or glycoproteins • Interferons(IFNs) • IFNa,IFNb – virally infected cells • IFNg – activated T-cells • Interleukins(Ils) • IL-1 to IL-5 • Direct other cells to divide and differentiate • Act on cells that express the correct IL receptor
colony stimulating factor
• Direct division and differentiation of bone marrow stem cells,
blood leukocyte stem cells, and further differentiation of some
cells outside the bone marrow.
• Other cytokines
• Tumor Necrosis Factor
• TNFa, TNFb
• Transforming Growth Factor
• TGFb
• Mediators of inflammation and cytotoxic reactions
Antibody
• Specifically binds to Ag • Binding region diversity • Mediates secondary effects • Soluble form of B-cell Ag receptor • Immunoglobulin • Fab portion binds Ag • Fc portion binds with other immune elements, e.g. phagocytes, complement • Act as opsonins
neutralization
– Ab binds to pathogen preventing
infection
phagocytosis
• Phagocytosis – Ingestion and destruction of
antigenic material
• Ab can activate complement or act as an opsonin
• Phagocyte binds to opsonized Ag
• Pseudopodia fuse with Ag enjulfing and internalizing it
(endocytosis)
• Reactive oxygen intermediates (ROIs) secreted by
phagosome
• PMNs contain lactoferrin
• Lysosomal granules=>enzymatic degradation
