Lymphatic and Immune System Flashcards
(82 cards)
1
Q
What is the immune system?
A
not an organ system, but a cell
population that inhabits all organs and defends the
body from agents of disease
2
Q
What is the lymphatic system and what does it do?
A
- Network of organs and vein-like vessels that recover fluid
- Inspect it for disease agents
- Activate immune responses
- Return fluid to the bloodstream
Introduction
3
Q
How does fluid recovery work?
A
Fluid continually filters from the blood capillaries into
the tissue spaces
* Blood capillaries reabsorb 85%
* 15% (2 to 4 L/day) of the water and about half of the
plasma proteins enter the lymphatic system and then are
returned to the blood
The Lymphatic System
4
Q
How does the immunity portion of the lymphatic system work?
A
– Excess filtered fluid picks up foreign cells and chemicals
from the tissues
* Passes through lymph nodes where immune cells stand
guard against foreign matter
* Activates a protective immune response
5
Q
How does the lipid absorption portion of the lymphatic system work?
A
– Lacteals in small intestine absorb dietary lipids that are
not absorbed by the blood capillaries
The Lymphatic System
6
Q
What is lymph?
A
the recovered fluid
7
Q
What do lymphatic vessels do?
A
transport lymph
8
Q
What are lymphatic tissues?
A
– Composed of aggregates of lymphocytes and
macrophages that populate many organs in the body; not confined
9
Q
What are lymphatic organs?
A
– Defense cells are especially concentrated in these
organs
– Separated from surrounding organs by connective
tissue capsules
10
Q
What is the composition of lymph?
A
– Clear, colorless fluid, similar to plasma, but much
less protein
– Originates as extracellular fluid drawn into lymphatic
capillaries
– Chemical composition varies in different places (in
intestines, after lymph nodes)
11
Q
What are lymphatic capillaries?
A
– Penetrate nearly every tissue of the body
* Absent from central nervous system, cartilage, cornea,
bone, and bone marrow
– Endothelium creates valve-like flaps that open when
interstitial fluid pressure is high, and close when it is lo
12
Q
Where do lymphatic vessels empty?
A
lymphatic trunks
13
Q
Where do lymphatic trunks empty?
A
lymphatic duct
14
Q
What are the two collecting ducts?
A
right lymphatic and thoracic
15
Q
Where does the right lymphatic duct collect from?
A
right arm, right side of head, empties into right subclavian vein
16
Q
Where does the thoracic duct collect from?
A
below diaphragm and left side, empties into left subclavian vein
17
Q
What moves lymph?
A
smooth muscle contraction
18
Q
What aids the flow of lymph?
A
skeletal muscle pump, thoracic pump from abdominal to thoracic cavity, flow in subclavian
19
Q
What are NK cells?
A
– Large lymphocytes that attack and destroy bacteria,
transplanted tissue, host cells infected with viruses or
that have turned cancerous
20
Q
What are T Cells?
A
mature in thymus
21
Q
What are B cells?
A
– Activation causes proliferation and differentiation into
plasma cells that produce antibodies
22
Q
What are macrophages?
A
– Large, avidly phagocytic cells of connective tissue
– Develop from monocytes
– Phagocytize tissue debris, dead neutrophils, bacteria,
and other foreign matter
– Process foreign matter and display antigenic fragments
to certain T cells alerting immune system to the
presence of the enemy
– Antigen-presenting cells (APCs)
23
Q
What are dendritic cells?
A
– Branched, mobile APCs found in epidermis, mucous
membranes, and lymphatic organs
– Alert immune system to pathogens that have breached
the body surface
– After internalizing the antigen they migrate to lymph
nodes to activate immune reaction
24
Q
What are reticular cells?
A
– Branched stationary cells that contribute to the stroma
of a lymphatic organ
25
What are lymphatic nodules?
– Dense masses of lymphocytes and macrophages that
congregate in response to pathogens
– Constant feature of the lymph nodes, tonsils, and
appendix
26
What are the primary lymphatic organs?
red bone marrow and thymus
27
What is the function of the primary lymphatic organs?
– Site where T and B cells become immunocompetent:
able to recognize and respond to antigens
28
What are the secondary lymphatic organs?
lymph nodes, tonsils, and spleen
29
What is the red bone marrow function?
hemopoiesis and immunity
30
What is the thymus function?
houses developing lymphocytes and secretes hormones regulating activity
31
What are the lymph node functions?
cleanse the lymph and activate t and b cells
32
What are the functions of the tonsils?
guard against ingested or inhaled pathogens
33
What are the 3 sets of tonsils?
Palatine, Lingual, and Pharyngeal (adenoid)
34
What does the spleen do?
filter and clean blood; – Healthy red blood cells (RBCs) come and go
– For old, fragile RBCs, spleen is “erythrocyte graveyard”
– Blood cell production in fetus (and very anemic adults)
– White pulp monitors blood for foreign antigens and
keeps an army of monocytes for release when needed
– Stabilizes blood volume through plasma transfers to
lymphatic system
35
What is a pathogen?
agent capable of producing disease
36
What are the lines of defense against pathogens?
– First line of defense: skin and mucous membranes
– Second line of defense: several nonspecific defense
mechanisms
* Leukocytes and macrophages, antimicrobial proteins,
natural killer cells, inflammation, and fever
– Third line of defense: the immune system
* Defeats a pathogen, and leaves the body with a “memory”
of it so it can defeat it faster in the future
37
What does the skin do to defend?
Acts as a barrier
38
What do the mucous membranes do to defend?
trap in mucous
39
What are phagocytes?
cells that engulf foreign matter
40
What are the 5 types of WBCs?
– Neutrophils
– Eosinophils
– Basophils
– Monocytes
– Lymphocytes
41
What do neutrophils do?
– Wander in connective tissue killing bacteria
– Can kill using phagocytosis and digestion
– Can kill by producing a cloud of bactericidal chemicals
* Lysosomes degranulate—discharge enzymes into
tissue fluid causing a respiratory burst
* Creates a killing zone around neutrophil, destroying
several bacteria
42
What do eosinophils do?
– Found especially in mucous membranes
– Guard against parasites, allergens (allergy-causing
agents), and other pathogens
– Kill tapeworms and roundworms by producing
superoxide, hydrogen peroxide, and toxic proteins
– Promote action of basophils and mast cells
– Phagocytize antigen–antibody complexes
– Limit action of histamine and other inflammatory
chemicals
43
What do basophils do?
– Secrete chemicals that aid mobility and action of other
leukocytes
– Leukotrienes: activate and attract neutrophils and
eosinophils
– Histamine: a vasodilator, which increases blood flow
* Speeds delivery of leukocytes to the area
– Heparin: inhibits clot formation
* Clots would impede leukocyte mobility
* Mast cells also secrete these substances
– Type of connective tissue cell very similar to basophils
44
What do lymphocytes do?
– Three basic categories: T, B, and NK cells
– Circulating blood contains
* 80% T cells
* 15% B cells
* 5% NK cells
– Many diverse functions
45
What do monocytes do?
emigrate from the blood into
connective tissues and transform into macrophages
46
What do the macrophages do?
all the body’s avidly
phagocytic cells, except leukocytes
– Wandering macrophages: actively seek pathogens
* Widely distributed in loose connective tissue
– Fixed macrophages: phagocytize only pathogens that
come to them
* Microglia—in central nervous system
* Alveolar macrophages—in lungs
* Hepatic macrophages—in liver
47
What are interferons?
—secreted by certain cells
(leukocytes) infected by viruses
– Of no benefit to the cell that secretes them
– Alert neighboring cells and protect them from
becoming infected
– Bind to surface receptors on neighboring cells
* Activate second-messenger systems within
– The alerted cell synthesizes various proteins that
defend it from infection
* Breaks down viral genes or prevents replication
– Also activates NK cells and macrophages
* Destroy infected cell before they can liberate a
swarm of newly replicated viruses
– Activated NK cells destroy malignant cells
48
What do NK cells do?
Natural killer (NK) cells continually patrol body looking
for pathogens and diseased host cells
* NK cells attack and destroy bacteria, transplanted
cells, cells infected with viruses, and cancer cells
* Recognize enemy cell and bind to it
* Release proteins called perforins
– Polymerize a ring and create a hole in its plasma
membrane
* Secrete a group of protein-degrading enzymes—
granzymes
– Enter through pore and degrade cellular enzymes and
induce apoptosis (programmed cell death)
not specific, innate
49
What is the fever function?
– Promotes interferon activity
– Elevates metabolic rate and accelerates tissue repair
– Inhibits reproduction of bacteria and viruses
50
What is the function of inflammation?
– Limits spread of pathogens, then destroys them
– Removes debris from damaged tissue
– Initiates tissue repair
51
What do neutrophils do to mobilize?
margination, accumulate at injury
52
What are monocytes the primary agents of?
tissue cleanup and repair
53
What are the distinguishing immunity characteristics?
Specificity and memory
54
What are the types of immunity?
cellular and humoral
55
What is cellular immunity?
Lymphocytes directly attack and destroy foreign cells
or diseased host cells
* Rids the body of pathogens that reside inside human
cells, where they are inaccessible to antibodies
* Kills cells that harbor them
56
What is humoral immunity?
* Mediated by antibodies that do not directly destroy a
pathogen but tag it for destruction
* Many antibodies are dissolved in body fluids
(“humors”)
* Can only work against the extracellular stages of
infections by microorganisms
57
What are the forms of immunity?
natural active and passive, artificial active and passive
58
What is natural passive immunity?
– Temporary immunity that results from antibodies
produced by another person
* Fetus acquires antibodies from mother through placenta,
milk
59
What is natural active immunity?
– Production of one’s own antibodies or T cells as a result
of infection or natural exposure to antigen
60
What is artificial active immunity?
– Production of one’s own antibodies or T cells as a result
of vaccination against disease
61
What is artificial passive immunity?
– Temporary immunity that results from the injection of
immune serum (antibodies) from another person or
animal
* Treatment for snakebite, botulism, rabies, tetanus, and
other diseases
62
What is an antigen?
any molecule that triggers an immune
response
63
What is an epitope?
—certain
regions of an antigen molecule that stimulate
immune responses
64
What are the cells in cellular immunity?
* Cytotoxic T (TC) cells: killer T cells (T8, CD8, or CD8+)
– “Effectors” of cellular immunity; carry out attack on enemy
cells
* Helper T (TH) cells (CD4)
– Help promote TC cell and B cell action and nonspecific
resistance
* Regulatory T (TR) cells: T-regs
– Inhibit multiplication and cytokine secretion by other T
cells; limit immune response
– Like TH cells, TR cells can be called T4, CD4, CD4+
* Memory T (TM) cells
– Descend from the cytotoxic T cells
– Responsible for memory in cellular immunity
65
What are the life stages of a T Cell?
– Born in bone barrow
– Educated in thymus
– Deployed to carry out immune function
66
What do T Cells do?
– T cells that fail are eliminated by negative selection
* Clonal deletion—self-reactive T cells die and
macrophages phagocytize them
* Anergy—self-reactive T cells remain alive but
unresponsive
* Negative selection leaves the body in a state of self-
tolerance—the surviving T cells respond only to
suspicious antigens (ignoring the body’s own proteins)
– Only 2% of T cells pass the test
* Naive lymphocyte pool: immunocompetent T cells
that have not yet encountered foreign antigens
* Deployment
– Naive T cells leave thymus and colonize lymphatic
tissues and organs everywhere in the body
67
What do B cells do?
* B cells develop in bone
– Some fetal stem cells remain in bone marrow and
differentiate into B cells
* B cells that react to self-antigens undergo either
anergy or clonal deletion, same as T cell selection
* Self-tolerant B cells synthesize antigen surface
receptors, divide rapidly, produce immunocompetent
clones
* Leave bone marrow and colonize same lymphatic
tissues and organs as T cells
68
What are APCS? What are the 3?
macrophages, dendritic, B cells
– Act as cell “identification tags” that label every cell of your
body as belonging to you
* Antigen processing
– APC encounters antigen
– Internalizes it by endocytosis
– Digests it into molecular fragments
– Displays relevant fragments (epitopes) in the grooves
of the MHC protein
– Wandering T cells inspect APCs for displayed antigens
– If APC only displays a self-antigen, the T cell disregards
it
– If APC displays a nonself-antigen, the T cell initiates an
immune attack
69
What is MHC 1?
* Constantly produced by nucleated cells,
transported to, and inserted on plasma membrane
* If they are normal self-antigens, they do not elicit a
T cell response
* If they are viral proteins or abnormal cancer
antigens, they do elicit a T cell response
– Infected or malignant cells are then destroyed before
they can do further harm to the body
70
What is MHC 2?
* Occur only on APCs and display only foreign
antigens
71
What is T Cell activation?
– Begins when TC or TH cell binds to a MHCP
displaying an epitope that the T cell is
programmed to recognize
– T cell must then bind to another APC protein
related to the interleukins
– T cell must check twice to see if it is really bound
to a foreign antigen—costimulation
* Helps ensure the immune system does not launch an
attack in the absence of an enemy
* Would turn against one’s own body and injure our
tissues
* Successful costimulation will trigger clonal
selection
– Activated T cell undergoes repeated mitosis
– Gives rise to a clone of identical T cells
programmed against the same epitope
– Some cells of the clone become effector cells
and carry out the attack
– Other cells become memory T cells
72
What makes T cells attack?
* When TC cell recognizes a complex of antigen
and MHC-I protein on a diseased or foreign
cell, it “docks” on that cell
73
What happens in the attack phase?
* Helper and cytotoxic T cells play different roles in the
attack phase of cellular immunity
* Helper T cells play central role in coordinating both
cellular and humoral immunity
* When helper T cell recognizes the Ag-MHCP complex:
– Secretes interleukins that exert three effects
* Attract neutrophils and NK cells
* Attract macrophages, stimulate their phagocytic activity,
and inhibit them from leaving the area
* Stimulate T and B cell mitosis and maturation
74
What does immune memory follow?
primary response
75
What can T cells do?
recall a pathogen
76
What does humoral immunity do?
* Humoral immunity is a more indirect method of
defense than cellular immunity
* B lymphocytes of humoral immunity produce
antibodies that bind to antigens and tag them for
destruction by other means
– Cellular immunity attacks the enemy cells directly
* Works in three stages like cellular immunity
– Recognition
– Attack
– Memory
77
How does humoral recognition work?
– Immunocompetent B cell has thousands of
surface receptors for one antigen
– Activation begins when an antigen binds to
several of these receptors, links them together and
is taken into the cell by receptor-mediated
endocytosis
* Small molecules are not antigenic because they
cannot link multiple receptors together
– B cell processes (digests) the antigen
* Links some of the epitopes to its MHC-II proteins
– Displays these on the cell surface
78
What happens in the attack phase of humoral?
* Immunoglobulin (Ig)—an antibody—a defensive
gamma globulin found in blood plasma, tissue fluids,
body secretions, and some leukocyte membranes
79
What are the actions of the 5 classes of immunoglobins?
* Neutralizing antigen
– The binding neutralizes toxins and prevents attachment of
viruses to body cells
* Immobilizing bacteria
– Cause bacteria to lose their motility
* Agglutinating and precipitating antigen
– Two antigen binding sites, causing agglutination
– Phagocytic cells ingest agglutinated microbes more readily
* Activating complement
– Antigen–antibody complexes activate complement proteins
* Enhancing phagocytosis
– Once antigens have bound to an antibody, the antibody acts
as a “flag” that attracts phagocytes.
80
What is the primary immune response?
immune reaction
brought about by the first exposure to an antigen, leaves an immune memory
81
What increases with secondary response?
IgG
82
What appears first in primary response?
IgM, IgG rises as it declines
