CHAPTER 22 Flashcards
Lymph
Fluid similar to plasma (without plasma proteins)
Lymphatic Vessels
a. lymphatic capillaries
b. lymphatic trunks
c. lymphatic ducts
Cells in the lymphatic system
lymphocytes, phagocytes, other cells
Lymphoid tissues
EX
a) tonsils
b) MALT (mucosa associated lymphatic tissue)
Lymphoid organs
spleen, thymus, lymph nodes
What does the lymphatic system do?
Protect us against disease
What do lymphatic system calls respond to?
Pathogens (viruses, bacteria, fungi, parasites)
Toxins
abnormal body cells such as cancers.
What is immunity, and what is involved in the immune system?
immunity is the ability to resist infection and disease
all cells and tissues are involved in production in immunity, NOT just lymphatic system
Which is greater, immune or lymphatic system?
IMMUNE SYSTEM
Specific defenses of lymphocytes
part of the immune response
identify, attack, and develop immunity to a specific pathogen
Non-specific defenses
block or attack any potential infectious organism. cannot distinguish one attack from another
Function of the lymphatic system
To produce, maintain, and distribute lymphocytes
Lymphocyte production
lymphocytes are produced in:
- lymphoid tissues (tonsils)
- lymphoid organs (spleen, thymus)
- red bone marrow
Lymphocyte circulation
from blood to interstitial fluid thru capillaries
-returns to venous blood thru lymphatic vessels
Fluid circulation
- from blood plasma to lymph and back to the venous system
- transports hormones, nutrients, and waste products
Difference between lymphatic and blood capillaries
lymphatic capillaries:
a. originate as pockets
b. large diameter
c. thinner wall
d. irregular shape in cross section
e. have lymphatic valves
Lymph flow
from lymphatic capillaries to larger lymphatic vessels containing one way valves
Lacteals
special lymphatic capillaries in small intestine, transport lipids from digestive tract
2 lymphatic ducts:
thoracic and right lymphatic duct
Thoracic duct
a. drainage areas including the left upper and whole lower body
b. entering venous system in the left subclavian vein, the superior vena cava and right atrium
c. enlarged site is called cisterns chyli
Right lymphatic duct
a. drainage areas including right upper of the body
b. entering right subclavian vein, then superior vena cava and right atrium
What percent of white blood cells are lymphocytes?
20-30% of WBC
T cellls
80% thymus dependent cells
a. cytotoxic t cells: cell mediated immunity
b. helper t cells: stimulate t and b cells
c. suppressor t cells: inhibit t and b cells
B cells
(10-15%) bone marrow derived cells
- antibody (Ab) - mediated immunity (humoral immunity)
- differentiate into plasma cells to produce Ab
- ab also called immunoglobulins
- life span of b lymphocytes4-20 years
NK cells
5-10% natural killer cells
a. also called: large granular lymphocytes
b. act as immunological surveillance
Cytotoxic T Cells
- attack cells infected by viruses
- produce cell mediated immunity
Memory T cells
formed in response to foreign substance
- remain in body to give immunity
Helper T cells
simulate function of t cells and b cells
Suppressor t cells
inhibit function of t cells and b cells
regulatory t cells
- are helper and suppressor t cells
- control sensitivity of immune response
What is lymphopoeisis
lymphocyte production
- lymphocyte production in red bone marrow
Hemocytoblasts-> Lymphoid stem cells = NK cells and B cells
- lymphocyte production in thymus (blood thymus barrier)
Lymphoid stem cells ————-> mature T cells
^ Thymic hormones (thymosins)
Lymphocyte production
called lymphopoiesis, involves
- bone marrow
- thymus
- peripheral lymphoid tissues
Hemocytoblasts differentiate into 2 groups
group 1. lymphoid stem cells:
remains in bone marrow and develop with help of stromal cells
-produces b cells and natural killer cells
group 2 lymphoid stem cells
- migrates to thymus
-produces t cells in environment isolated by blood thymus barrier
Lymphoid tissues
(storage of lymphocytes) without fibrous capsule
- lymphoid nodules:
a. respiratory tract
b. digestive t- ex. payer’s patch, appendix (MALT)
c. urinary tract
Tonsils
a. pharyngeal tonsil (adenoid tonsil) single
b. palatine tonsils: a pair (R & L)
c. Lingual tonsils: a pair (R & L)
Lymphoid organs
covered with capsule
1 lymph nodes:
2. thymus:
3. Spleen:
Mucosa Associated lymphoid tissues (MALT)
- lymphoid tissues associated with the digestive, respiratory, urinary, and reproductive tracts
ex. aggregated lymphoid nodules= peyer’s patch : cluster deep to intestinal epithelial lining - Appendix (vermiform appendix): contains a mass of fused lymphoid nodules
Lymph Nodes: Anatomy:
a. capsule= trabecular
b. afferent vessels
c. sub capsular sinus: d cells
Cortex:
a. outer cortex- D cells, b cells
b. germinal center- b cells
c. deep cortex- t cells
Medulla: b cells, plasma cells
Efferent vessel
Hilus
- D cells: dendritic cells
- function: initiating immune response
Functions of lymph nodes
a. acting as a filter, purifying lymph before it reaches the venous system
b. providing an early warning system for immune responses (by d cells)
c. producing antibodies (by b cells and plasma cells)
Important lymph nodes
a. Cervical lymph node
b. axillary lymph node
c. inguinal lymph node (groin areas)
lymph nodes in gut and trachea
Lymphadenopathy
enlargement of lymph node (sign of infection, cancer or endocrine disorder)
Lymph nodes and cancer cells
lymph nodes serve as “way stations” for migrating cancer cells (bc lymphatic capillaries offer litter resistance to the passage of cancer cells)
Thymus anatomy
Location: in the mediastinum
weight: 40 g (2 year old)–> 12 g (50 year old)
capsule –> 2 thymic lobes
*many lobules
Thymus cortex
(immature t cells, reticular epithelial cells) producing thymosins
Thymus medulla
mature t cells, REC and more macrophages
-REC encircle thymus (hassall’s) corpuscles
Hassle’s corscuples: epithelial cells, unknown function
Function of reticular epithelial cells (REC) or thymus
a. rec encircle the blood vessels and immature t cells, and maintain a blood thymus barrier in the cortex
b. rec secrete the thymic hormones (thymosins) for the maturation of t lymphocytes
Thymus Medulla Area
does not have blood thymus barrier. mature t lymphocytes can enter the blood stream or lymphatic vessels here
Reticular epithelial cells in the cortex of the thymus
- surround immature lymphocytes in cortex
- maintain blood thymus barrier
- secrete thymic hormones
Reticular epithelial cells in the medulla
- form concentric layers known as the thymic corpuscles= hassalls corpuscles
- the medulla has no blood thymus barrier
- mature t cells can enter or leave bloodstream
Where is the spleen located
the lateral border of the stomach, connected by gastro splenic ligament
Red pulp of spleen
recycle of red blood cells
-contains macrophages (major cells), RBCs, and some lymphocytes
White pulp of spleen
has a central artery
contains:
lymphocytes (major cells) in lymphoid nodules, and some macrophages AND dendritic cells (antigen presenting cells)
Spleen: Blood Pathway:
Splenic artery— Hilus– white pulp
—cappillaries(sinusoids)–red pulp (macrophages engulf old RBCs)– small veins– hilus–splenic veins
Spleen is the largest…
collection site of lymphoid tissues
Functions of spleen
a. removing abnormal blood cells and fragments (red pulp)
b. storing iron (Fe+2) recycled from old RBC’s (red pulp)
c. initiating immune responses by t & B cells (white pulp)
Innate (non specific) defenses
- always work the same way
- against any type of invading agent
- nonspecific resistance
Adaptive (specific) disease
- protect against specific pathogens
- depend on activities of lymphocytes
- specific resistance (immunity)
a. develops after exposure to environmental hazards
Nonspecific defenses (7)
- physical barriers
- phagocytes
- immunological surveillance (Nk cells(
4 interferons
5 complement
6 inflammatory response
7 fever
Non specific defenses– physical barriers
skin, hair, epithelium, mucus,, acids
non specific defenses: phagocytes:
microphages:from neutrophils and eosinophils
macrophages: from monocytes (reticulo-endothelial system)
a. fixed macrophages: (histiocytes) in bone marrow, connective tissue
- microglia: in CNS
- kupffer cells: in liver sinusoids
free macrophages: wandering macrophages. ex. alveolar macrophages-> dust cells
chemotaxis
WBCs or macrophages are attracted to the infected sites by chemicals released from other defense cells
Cells in the CNS
- neurons:
- neuroglial cells: (90%)
- astrocytes
- microglia
- ependymal cells
- oligodendrocytes
** No lymphatic capillary system in the CNS
Immunological surveillance (by NK cells)
a. against virus and cancer cells
b. NK cells release proteins (perforins) to lysis membranes of pathogenic cells
c. immunological escapes: NK cells have no effect for some cancer cells
Interferons
a. against viruses
b. released by lymphocytes, macrophages, and virus infected cells
c. one of the cytokines (chemicals released by tissue cells to response to local infections.) they can act as paracrine or endocrine hormones
3 types of interferons:
1 alpha - produced by leukocytes and virus infected cells - stimulate NK cells 2. beta -secreted by fibrocytes -slow inflammation 3 gamma - secreted by t cells and NK cells -stimulate macrophage activity
Complement (C) proteins
a.against bacteria
b. stimulate inflammation: (+) histamine release by mast cells
c/ attract phagocytes
d. enhance phagocytes
e. produced by liver PEOPLE WITH LIVER DISEASE HAVE LESS COMPLEMENT PROTEINS
Inflammation (inflammatory response)
- by mast cells (mobile connective tissue cells that release histamine and heparin)
- cardinal signs and symptoms: swelling, redness, heat and pain
Fever
- temp >37.2 C or 99 F
-temperature regulation center: (pre optic area) PO of hypothalamus - Pyrogen (& interleukin-1 = IL-1): a chemical released by macrophages to increase temperature
-The benefit of fever (if it is within a healthy limit):
a. Inhibit growth of bacteria or virus
b. (+) body metabolism
c. (+) mobilization of tissue defenses:
WBCs move faster
d. (+) tissue repair.
Specific defenses (Immune Response):
Innate immune and acquired immune
innate immune
present at birth
Acquired immune
Active Im: develops after exposure to antigen (Ag)
a. Induced A. Im: (ex. Vaccination)
b. Natural acquired A. Im:
Passive Im: produced by transfer of Ab from another source
a. Induced P. Im: (ex. injecting Ab to treat patient)
b. Natural acquired P. Im:
Properties of immunity (4)
- Specificity
- Versatility: abilities to face different Ags due to
diversity of lymphocytes - Memory
- Tolerance: not response to some Ags
Innate (Nonspecific) Defenses
Always work the same way
Against any type of invading agent
Nonspecific resistance
Adaptive (Specific) Defenses
Protect against specific pathogens
Depend on activities of lymphocytes
Specific resistance (immunity)
Develops after exposure to environmental hazards
Cell-mediated Immunity (by T cells):
- Ag presentation:a. By the presence of Ag-glycoprotein from foreign cells
b. By the membrane proteins (MHC: major histocompatibility
complex) of infected cells: MHC Class I
c. By the membrane proteins in Ag-presenting cells:
MHC Class II.
(ps): Ag presenting cells (APCs):
a. Free & fixed macrophages: in connective tissues, Kupffer cells (in liver), microglia (in CNS). b. Langerhans cells of skin, dendritic cells of lymph nodes & spleen.
- Ag recognition:
MHC Proteins
The membrane glycoproteins that bind to antigens
Genetically coded in chromosome 6
The major histocompatibility complex (MHC), our own cell membrane markers.
Differs among individuals
Class I (= MHC-I) vs Class II (= MHC-II):
Class I (= MHC-I): * Found in membranes of all nucleated cells
Class II (= MHC-II):
- Found in membranes of antigen-presenting cells (APCs)
- Found in lymphocytes
Ag recognition:
T cells & macrophages have cell membrane marker:
CD (closter of differentiation).
A. Tc, Ts: CD8—Class I MHC:
a. Release perforin (ATTACKS CELL MEMBRANE) b. Release lymphotoxin c. Release cytokines--- apoptosis (cell death) changes DNA and puts it into cell death d. Produce memory Tc cells B. TH: CD4 ----- Class II MHC: a. Produce memory T-helper cells b. Bind & activate B cells
CD Markers
- Also called cluster of differentiation markers
In T cell membranes
Molecular mechanism of antigen recognition
More than 70 types CD markers
- CD3 Receptor Complex
Found in all T cells
- Two Important CD Markers
- CD8 Markers
Found on cytotoxic T cells and suppressor T cells
Respond to antigens on Class I MHC proteins - CD4 Markers
Found on helper T cells
Respond to antigens on Class II MHC proteins
Antibody-mediated Immunity (by B cells)
- B cell sensitization:
a. By MHC II on B-cell membrane
b. By binding with activated T-helper cell - B cell activation:
a. Produce memory B cells
b. B cells become plasma cells
c. Plasma cells produce Abs
Hapten (Partial Antigens)
Must attach to a carrier molecule to act as a complete antigen
Dangers of Haptens
Antibodies produced will attack both hapten and carrier molecule
If carrier is “normal”:
Antibody attacks normal cells
For example, penicillin allergy
IgG:
IgG is the largest and most diverse class of antibodies
80 percent of all antibodies
IgG antibodies are responsible for resistance against many viruses, bacteria, and bacterial toxins
Can cross the placenta, and maternal IgG provides passive immunity to fetus during embryological development
Anti-Rh antibodies produced by Rh-negative mothers are also IgG antibodies and produce hemolytic disease of the newborn
IgE
attaches as an individual molecule to the exposed surfaces of basophils and mast cells
When an antigen is bound by IgE molecules:
The cell is stimulated to release histamine and other chemicals that accelerate inflammation in the immediate area
IgE is also important in the allergic response
IgD:
is an individual molecule on the surfaces of B cells, where it can bind antigens in the extracellular fluid
Binding can play a role in the sensitization of the B cell involved.
IgM:
the first class of antibody secreted after an antigen is encountered
IgM concentration declines as IgG production accelerates
Plasma cells secrete individual IgM molecules, but it polymerizes and circulates as a five-antibody starburst
The anti-A and anti-B antibodies responsible for the agglutination of incompatible blood types are IgM antibodies
IgM antibodies may also attack bacteria that are insensitive to IgG
IgA:
found primarily in glandular secretions such as mucus, tears, saliva, and semen
Attack pathogens before they gain access to internal tissues
IgA antibodies circulate in blood as individual molecules or in pairs
Epithelial cells absorb them from blood and attach a secretory piece, which confers solubility, before secreting IgA molecules onto the epithelial surface
Primary and Secondary Responses to Antigen Exposure
Occur in both cell-mediated and antibody-mediated immunity
First exposure (primary response)
IgM is weak. Take 2 weeks for IgG peak
Next exposure (secondary response)
IgG rises very high & quickly. Extends longer time.
IgM is also quicker and slightly extended
Memory cells already primed
Four Categories of Allergic Reactions
1 Immediate hypersensitivity: Type I
2 Cytotoxic reactions: Type II (ex. Blood typing)
3 Immune complex disorders: Type III
4 Delayed hypersensitivity :Type IV
(ex.poison ivy)
Type I Allergy (immediate hypersensitivity)
A rapid and severe response to the presence of an antigen
Includes allergic rhinitis (environmental allergies)
Production of large quantities of IgE antibodies
Massive inflammation of affected tissues
Allergens in bloodstream may cause anaphylaxis
Anaphylaxis
Can be fatal
* Affects cells throughout body
* Changes capillary permeability
Produces swelling (hives) on skin
* Smooth muscles of respiratory system contract
Make breathing difficult
* Peripheral vasodilatation
Can cause circulatory collapse
(= anaphylactic shock)Seven Functions of Ag–Ab Complexes
Neutralization of antigen binding sites Precipitation and agglutination - formation of immune complex 3. Activation of complement 4. Attraction of phagocytes 5. Opsonization increasing phagocyte efficiency 6. Stimulation of inflammation 7. Prevention of bacterial and viral adhesion
Combined Responses to Bacterial Infection
Neutrophils and NK cells begin killing bacteria Cytokines draw phagocytes to area Antigen presentation activates: Helper T cells Cytotoxic T cells B cells activate and differentiate Plasma cells increase antibody levels
Combined Responses to Viral Infection
Similar to bacterial infection
But cytotoxic T cells and NK cells are activated by contact with virus-infected cells
Cytokines
Chemical messengers involved in cellular immunity produced primarily by macrophages and lymphocytes.
Hormones and paracrine-like glycoproteins: (ex.)
Interferons
Interleukins
Tumor necrosis factors (TNFs)
Colony-stimulating factors (CSFs)
Immune System Development in Fetus
Fetus can produce immune response
Fetal thymus cells migrate to tissues that form T cells
Liver and bone marrow produce B cells
Four month fetus produces IgM antibodies
Before Birth
Maternal IgG antibodies
Pass through placenta
Provide passive immunity to fetus
GIVE THE BABY IGA IN THE FIRST TWO WEEKS. AT LEAST 2 WEEKS.
After Birth
Mother’s milk provides IgA antibodies
Stress and the Immune Response
Glucocorticoids Secreted to limit immune response Long-term secretion (chronic stress) Inhibits immune response Lowers resistance to disease
Immune system and age
Increasing vulnerability to infections and cancer
Four Effects of Aging
1Thymic hormone production is greatly reduced
2 T cells become less responsive to antigens
3 Fewer T cells & reducing responsiveness of B cells
4 Immune surveillance against tumor cells declines
Effects of Glucocorticoids
Depression of the inflammatory response
Reduction in abundance and activity of phagocytes
Inhibition of interleukin secretion
Tumor Necrosis Factors (TNFs)
TNFs slow the growth of a tumor and kill sensitive tumor cells
Activated macrophages secrete one type of TNF and carry the molecules in their plasma membranes
Cytotoxic T cells produce a different type of TNF
In addition to their effects on tumor cells:
TNFs stimulate granular leukocyte production, promote eosinophil activity, cause fever, and increase T cell sensitivity to interleukins
Phagocyte-Activating Chemicals
Several cytokines coordinate immune defenses by adjusting the activities of phagocytic cells
Include factors that attract free macrophages and microphages and prevent their premature departure from the site of an injury
Colony-Stimulating Factors
Factors are produced by active T cells, cells of the monocyte-macrophage group, endothelial cells, and fibrocytes
CSFs stimulate the production of blood cells in red bone marrow and lymphocytes in lymphoid tissues and organs
Immune Disorders
3
- Autoimmune disorders
- Immunodeficiency disease
- Allergies
Autoimmune Disorders
A malfunction of system that recognizes and ignores “normal” antigens
Activated B cells make autoantibodies against body cells
Examples:
Thyroiditis
Rheumatoid arthritis
Insulin-dependent diabetes mellitus (IDDM)
Immunodeficiency Diseases
Result from:
Problems with embryological development of lymphoid tissues
Can result in severe combined immunodeficiency disease (SCID)
Viral infections such as HIV
Can result in AIDS
Immunosuppressive drugs or radiation treatments
Can lead to complete immunological failure
HIV (human immunodeficiency viruses):
A. Attack T-helper cells (with CD4 coreceptors) and wipe
out immune system.
a. Release more viruses after an infected cell is dead.
b. cause infected cell releasing a chemical to block
other T cells to come.
c. inhibit MHC gene expression (avoiding be recognized
B. HIV are transferred by any internal body fluids. (200 millions/ a size of period) C. Treatments: a. AZT: inh. RNADNA (reverse transcription) b. Protease inhibitor: inhibits viral assembly c. Vaccine? Difficult due to Ag changes
Allergies
Inappropriate or excessive immune responses to antigens
allergens
Antigens that trigger allergic reactions
Allergy (or hypersensitivity):
Immediate hyper-sensitivity:
a. Produce symptom within second or minutes
b. mediated by B cells, Ag-Ab reaction
c. Produce IgE
d. secondary exposure to the Ag causing mast cells
to release histamine
e. ex. Food, bee stings, pollens, hay fever
f. Anaphylactive shock: decrease of blood pressure
acutely (ex. Penicillin allergy)
2. Delayed hypersensitivity:
a. Mediated by T cells (response hours later)
b. Ex. Poison ivy causing dermatitis
c. Secretion of lymphokines
d. Treatment: corticosteroids (not anti-histamines)
