Immune system Flashcards
What does the immune system do?
Protects us from infectious agents and harmful substances
Typically without our awareness
The immune system is composed of…
Numerous cellular and molecular functions working together
Infectious agents…
cause harm or kill host
5 categories of pathogen
bacteria
virus
parasites
fungi
protozoans
also prions sorta
Bacteria
single celled
prokaryotes, many are harmless
Virus
pieces of DNA or RNA in a protein shell
Able to enter your cells and your body will then reproduce them
Fungi
eukaryotic cells including mold, yeast, and spores
-Release proteolytic enzymes inducing inflammation
Protezoans
eukaryotic cells w/o cell wall (essentially a parasite)
Multicellular parasites
large and multicellular
◦ Take nourishment from host
Prions
fragments of infectious proteins that reproduce
◦ Cause diseases in nervous tissue
Leukocytes
White blood cells
Formed in red bone marrow
3 types of granulocytes
Neutrophils, eosinophils, basophils
2 types of agranulocyte
Monocytes and lymphocytes
What do monocytes become and why?
Macrophages when they leave the blood and enter tissues
types of lymphocyte
T, B and NK
What structures house immune cells?
Lymphatic tissue, select organs, Epithelial layers of skin and mucosal membranes
What do organs hold?
Macrophages. These macrophages may reside in one organ or be migrating macrophages
Epithelial layers of skin and mucosal
membranes house…
Dendritic cells; modified monocytes
Connective tissue house
mast cells
what are Cytokines
small proteins that regulate immune activity
Effects of cytokines
- Signaling cells (including non-immune cells, e.g., neurons)
- Controlling development and behavior of immune cells
- Regulating inflammatory response
- Destroying cells
4 categories of cytokines
Interleukins, tumor necrosis factor, colony stimulating factor and interferons
Innate immunity
Present at birth, protects against a variety of things (nonspecific). No prior exposure necessary, immediate response to harmful agents.
Adaptive immunity
Acquired immunity; response to antigen requires specific t and b lymphocytes; takes a several days to be effective
Characteristic of innate immunity
◦ Prevents entry of potentially harmful substances
◦ Responds nonspecifically to protect body
First line of defense is the…
Skin and mucosal membrane
◦ Skin releases antimicrobial substances
◦ Has normal nonpathogenic flora (microorganisms)
Mucosal membranes line..
body openings
◦ Produce mucin and release antimicrobial substances
◦ Lined by harmless bacteria that suppress growth of more virulent types
Other responses of innate immunity are:
coughing, sneezing, watery eyes, etc.
2nd line of defense:
cellular defense
Cells of innate immunity that engulf unwanted
substances by phagocytosis
Neutrophils, macrophages, and dendritic cells
Neutrophils and macrophages
destroy engulfed particles
Dendritic cells
destroy particles and then present
fragments as antigens for destruction by t-
lymphocytes
Basophils and mast cells promote
inflammation; Release chemicals that draw in fluid and attract immune cells
Histamine
increases vasodilation and capillary permeability
Heparin
acts as an anticoagulant
Eicosanoid
increases inflammation
Natural killer cells
destroy a variety of unwanted cells
◦ They kill by releasing cytotoxic chemicals
Perforin
stabs a hole in the unwanted cell
Granzymes
enter hole and cause apoptosis
Eosinophils
Attack multicellular parasites;
Pattern recognition receptors on cell surface bind to patterns on microbe surface and releases cytotoxic chemicals
Antimicrobial proteins
function against microbes by activating and recruiting multiple immune cells and causing inflammation
Inflammation
an immediate response to ward off unwanted substances
◦ Local, nonspecific response of vascularized tissue to injury
Events of inflammation
Injured tissue, basophils, mast cells, and infectious organisms release chemicals that initiate response
Step 1 of inflammation
Released chemicals cause vascular changes
◦ Vasodilation, increased capillary permeability, increased CAMs
◦ Cell adhesion molecules (CAMs) – site for leukocyte attachment
Step 2 of inflammation
Recruitment of leukocytes
◦ Margination
◦ Diapedesis
◦ Chemotaxis
Step 3 of inflammation
Delivery of plasma proteins to site
◦ Immunoglobulins, complement, clotting proteins, and kinins
◦ Kinins stimulate pain receptors
Effects of inflammation
Fluid moves from blood to injured or infected area along with protein and immune cells
-Vasodilation
-Increased capillary permeability
Extra fluid is taken up by lymphatic capillaries in the area (“washing”)
◦ Carries away debris and allows lymph node monitoring of its contents
Cardinal signs of inflamation
redness
swelling
heat
pain
loss of function
Acute inflammation lasts about
8-10 days
Fever is also known as…
pyrexia
What is a fever?
Abnormal body temperature elevation
◦ 1°C or more from normal (37°C)
◦ Results from the release of pyrogens from immune cells or infectious agents
◦ Travel to hypothalamus which raises temperature set point
Events of fever
Onset: Temp begins to rise
Stadium: Elevated temperature is maintained
Defeverescence: time when temperature returns to normal
Benefits of fever
◦ Inhibits reproduction of bacteria and
viruses
◦ Promotes cytokine release activity
◦ Increases activity of adaptive immunity
◦ Accelerates tissue repair
◦ Increases CAMs on endothelium of
capillaries in lymph nodes
◦ Additional immune cells migrating
out of blood
◦ Recommended to leave a low fever
untreated
Adaptive immunity involves:
specific lymphocyte responses to an antigen
◦ Contact with antigen causes lymphocyte proliferation
◦ Longer response time then innate immunity
◦ Takes days to develop
2 branches of adaptive immunity
◦ Cell-mediated immunity involving T-lymphocytes
◦ Humoral immunity involving B-lymphocytes, plasma cells, and antibodies
Pathogens are detected by lymphocytes because they contain…
antigens
Antigen
substance on cell surface that binds a lymphocyte or antibody
Foreign antigens
differ from human body’s molecules
◦ Bind body’s immune components
Self-antigens
are body’s own molecules
◦ Typically do not bind immune components
Antigenic determinant
◦ Specific site on antigen recognized by immune system
◦ Each has a different shape
◦ Pathogenic organisms can have multiple
Immunogen
antigen that induces an immune response
Haptens
foreign molecules that induce immune
response when attached to a carrier molecule in host
◦ Too small to be an immunogen alone
◦ E.g., toxin in poison ivy
T- and B-lymphocytes have unique…
Receptor complexes;
About 100,000 per cell, specific for one antigen
Lymphocyte contact with antigen
◦ B-lymphocytes make direct contact with antigen
◦ T-lymphocytes have antigen presented by another
(your body) cell
cytoxic T-cell
Helper T-cell
Cytotoxic T-cell
destroy invaders
Helper T-cell
recruit other immune cells
3 main events of lymphocytes life
- Formation and maturation of lymphocytes
- Activation of lymphocytes
- Effector response: action of lymphocytes to
eliminate antigen
Cell-mediated immunity
describes a pathway that does not result in antibody
production but instead utilizes T-lymphocytes and targets endogenous antigens
◦ Helper-T-cells identify these cells
◦ Cytotoxic-T-cells which can destroy the virus-infected cell by apoptosis
Humoral immunity
describes the pathway by which antibodies are produced by B-lymphocytes to target exogenous (foreign) antigens
B-lymphocytes can be activated by
helper-T cells or by binding to a foreign antigen
◦ Begin production of antibodies
◦ These antibodies can bind to cells with the foreign antigen
Margination
adherence of leukocytes to CAMs
Diapedesis
cells escape blood vessel walls
chemotaxis
leukocytes migrate toward chemicals released from damaged cells
