The Lymphatic System and Immunity Flashcards
Pathogens
Disease-causing organism
Immunity
The ability to resist infection and disease
Lymphatic vessels
Carry lymph from peripheral tissues to the venous system
Lymph
Interstitial fluid that has entered lymphatic vessels
How do lymphatic capillaries differ from blood capillaries?
Lymphatic capillaries:
- Closed at one end
- Have larger luminal diameters
- Have thinner walls
What lines lymphatic capillaries?
Endothelial cells but the basement membrane is incomplete or absent
Lymphatic system
- Lymph
- Lymphatic vessels
- Lymphoid tissues and organs
- Lymphoid cells
Small lymphatic vessels
- 3 layers
- Valves that help lymph move since limited pressure
Two sets of lymphatic vessels
Superficial lymphatics and deep lymphatics
Deep lymphatics
Larger lymphatic vessels that accompany deep arteries and veins supplying skeletal muscles and other organs of the neck, limbs, and trunk and the walls of the visceral organs
Superficial lymphatics
In subcutaneous layer
Lymphatic trunks
Convergence of superficial and deep lymphatics
Thoracic duct
Collects lymph from the lower body and upper right body
Right lymphatic duct
Collects lymph from upper right side
Cisterna chyli
Saclike chamber that receives lymph from the inferior part of the abdomen, pelvis, and lower limbs
Lymphedema
Obstruction of lymphatic vessels
Lymphoid cells
Consist of immune cells found in lymphoid tissues and the cells that support those tissues
Phagocytes
Macrophages and microphages
Lymphocytes
Respond to specific invading pathogens, abnormal body cells and foreign proteins
Classes of lymphocytes
- T cells
- B cells
- NK cells
Lymphoid tissues
Connective tissues dominated by lymphocytes
Lymphoid nodule
The lymphocytes are densely packed in an areolar tissue
Tonsils
Large lymphoid nodules in the walls of the pharynx
Pharyngeal tonsils, adenoid
Lies in the posterior superior wall of the nasopharynx
Palatine tonsils
Left and right palatine tonsils are located at the posterior, inferior margin of the oral cavity
Lingual tonsils
Lie deep to the mucous epithelium covering the base of the tongue
Tonsilitis
Inflammation of the tonsils, especially palatine tonsils
Mucosa-associated lymphoid tissue (MALT)
Collection of lymphoid tissue that protect the epithelia of the digestive, respiratory, urinary and reproductive systems
Aggregated lymphoid nodules
Cluster of lymphoid nodules deep to the epithelial lining of the intestines
Lymphoid organs
Lymph nodes, thymus and spleen
What covers each lymph node?
A dense connective tissue capsule
Trabeculae
Bundles of collagen fibres that extend from the capsule into the interior of the node
Hilum
Shallow indentation
Afferent lymphatics
- Bring lymph to the lymph node from peripheral tissues
- Opposite the hilum
Efferent lymphatics
- Leave the lymph node at the hilum
- Carry lymph away from the lymph node towards venous circulation
Lymph flow
Subcapsular space > cortex > paracortex > medulla > sinuses > efferent lymphatics
Subcapsular space
Contains a meshwork of branching reticular fibers, macrophages and dendritic cells
Cortex
Periphery of cortex contains B cells with germinal centres
Paracortex
- Dominated by T cells
- Where lymphocytes leave blood stream and enter lymph node
Medulla
Contains B cells and macrophages
Lymph node function
Filters lymph before it reaches veins
Septa
Fibrous partitions that divide lobes into lobules
Lobule
Consists of an outer cortex densely packed with lymphocytes and a medulla
Lymphocytes in the cortex of the lobule
Form thymic corpuscules
Function of the thymus
- The cortex contains actively diving T cells > medulla > medullary blood vessel > blood stream
- Epithelial reticular cells maintain blood thymus barrier
Which organ contains the largest collection of lymphoid tissue in the body?
Spleen
Functions of spleen
- Removing abnormal blood cells
- Storing iron recycled from RBCs
- Initiating immune responses by B and T cells
Gastrosplenic ligament
Attaches stomach to spleen
Hilum
Groove marking the border between the gastric and renal areas
Red pulp
Contains large quantities of RBCs
White pulp
Resembles lymphoid nodules
Trabecular arteries
Splenic artery > trabecular arteries > smaller (surrounded by white pulp) > discharge blood into red pulp
Cell population of red pulp
Normal components of circulating blood
Fixed and free macrophages
Trabecular veins
Reticular fibres > sinusoids > small veins > trabecular veins
Why is the spleen difficult to repair?
Sutures tear out before they have been tensed enough to stop bleeding
Immune response
The body’s reaction to infectious agents and other abnormal substances
Resistance
The ability of the body to maintain its immunity
2 types of immunity
- Innate (nonspecific) immunity
2. Adaptive (specific) immunity
Innate (nonspecific) immunity
- Physical barriers and internal defence processes that we are born with
- Nonspecific: doesn’t distinguish
- NK cells
Adaptive (specific) immunity
- T cells and B cells
- Specific/particular
What are most lymphocytes?
T cells
Lymphocytopoiesis
Hemocytoblasts divide in red bone marrow > lymphoid stem cells produced
Red bone marrow > B cells and NK cells
Thymus > T cells
Innate defenses
- Physical defences
- Phagocytes
- Immune surveillance
- Interferons
- Complement
- Inflammation
- Fever
Physical defenses
Epithelia of skin and mucous membrane, secretions and hairs
Phagocytes
Remove cellular debris and respond to invasion by foreign substances or pathogens
Microphages
- Neutrophils: phagocytize cellular debris or bacteria
- Eosinophils: target foreign substances coated with antibodies
Macrophage functions
- Engulf pathogens
- Binds to or removes pathogen with help
- Releasing chemicals
Fixed macrophages
Reside in specific tissues or organs
Free macrophages
Travel throughout the body
Chemotaxis
Free macrophages and microphages attracted to or repelled to surrounding fluids
Adhesions
Free macrophages and microphages begin with adhesion
When phagocytes attach to their target
Immune surveillance
NK cells continual policing peripheral tissues
NK cells
- Recognition and adhesion
- Realignment of golgi apparatus - trans face points towards abnormal cell, golgi appartus creates perforin
- Secretion of perforin
- Lysis of abnormal cells
Tumour-specific antigens
In the plasma membrane of cancer cells
Immunological escape
When abnormal cells avoid detection or neutralise body defenses
Interferons (IFNs)
Small proteins released by activated lymphocytes and macrophages and by tissue cells infected with viruses
Interferons process
Interferons bind to surface receptors on the membrane of a normal cell and by second messengers, triggers the production of antiviral proteins
Antiviral proteins
Interferon with viral replication inside the cell
Interferon alpha
Produced by cells infected with viruses
Attracts and stimulates NK cells and enhances resistance to viral infection
Interferon beta
Secreted by fibroblasts and slows inflammation in a damaged area
Interferon gamma
Secreted by T cells and NK cells and stimulates macrophage activity
Cytokines
Chemicals that tissue cells release to coordinate local activities
Classical pathway
Most effective activation of the complement system
- Antibodies bind to bacterial cell wall
- Attachment of C1 to 2 antibodies
- Activation and cascade
- C3b binds to cell wall and enhances phagocytosis
Lectin pathway
Activated by protein MBL which binds to carbohydrates on bacterial surfaces
- Lectin binds to bacterial cell wall
- C3 activation
- C3b binds to bacterial surface and enhances phagocytosis
Alternative pathway
Important in the defence against bacteria, some parasites and virus-infected cells
- Complement proteins interact in plasma
- C3b protein binds to the bacterial cell wall
Complement activation causes
- Cell lysis (MAC)
- Opsonisation (enhancement of phagocytosis)
- Inflammation (histamine release)
Inflammation
Localised tissue response to injury
Cardinal signs and symptoms of inflammation
Local redness, swelling, heat and pain
Mast cells
Release histamine, heparin and prostaglandins
Inflammation and steps in tissue repair
- Tissue damage, chemical change in interstitial fluid
- Mast cells
- Cardinal signs of inflammation, phagocyte attraction > release of cytokines
Nercorsis
Tissue destruction after cells have been injured or destroyed
Abscess
Accumulation of pus in an enclosed tissue
Fever
Body temperature greater than 37.2 degrees, 99 F
Pryogens
Fever-inducing agents
Benefits of fever
Higher metabolic rate
Adaptive immunity lymphocytes
- Cytotoxic T cells
- Helper T cells
- Regulatory T cells
- Memory T cells
Cytotoxic T cells
Involved in direct cellular attack
Enter peripheral tissues and attack antigens physically and chemically
Helper T cells
Stimulate the response of both T and B cells
What is largely responsible for the loss of immunity in AIDS?
Reduction in helper T cells
Regulatory T cells
Subset of T cels that moderate the immune response
Memory T cells
Respond to antigens they have already encountered by cloning lymphocytes
Cell mediated immunity
Cytotoxic T cells
Antibody-mediated immunity
B cells
What triggers the immune response?
Specific antigens
What are most antigens?
Pathogens, parts or products of pathogens or foreign substances
Usually proteins
When does a lymphocyte become activated?
When it has contact with an appropriate antigen
What happens to an activated lymphocyte?
It begins to divide, producing more lymphocytes with the same specificity
Clone
All the identical cells produced by lymphocyte divisions
Clonal selection
Process of an antigen selecting particular lymphocytes for cloning
Active immunity
Develops after exposure to an antigen
Body responds to to antigen by making its own antibody
Naturally acquired active immunity
Normally begins to develop after birth
Artificially acquired active immunity
Stimulates the body to produce antibodies under controlled conditions
Passive immunity
Produced by transferring antibodies from another source
Naturally acquired passive immunity
A baby receives antibodies from the mother during gestation or through breast milk
Artificially acquired passive immunity
Person receives antibodies to fight infection or prevent disease
Properties of adaptive immunity
- Specificity
- Versatility
- Memory
- Tolerance
Specific defence
Activated by specific antigens
The immune response targets that particular antigens and no others
Specificity
Results from activation of appropriate lymphocytes and the production of antibodies with targeted effects
How does specificity occur?
T cells and B cells respond to the molecular structure of an antigen
Versatility
Diversity of lymphocytes present in the body
Memory
Lymphocyte divisions produce two groups of cells
One group attacks the invader immediately
Another group remains inactive unless it meets the same antigen at a later date
Tolerance
Tolerance towards self-antigens
MHC proteins
Membrane glycoproteins
Antigen presentation
Occurs when an antigen-MHC protein combination capable of activating T cells appear in the plasma membrane
Classes of MHC
Class I: In all nucleated body cells
Class II: Present only in plasma membranes of antigen-presenting cells and lymphoctes
Antigen-presenting cells
Engulf and break down pathogens or foreign antigens
Antigen processing
Creates fragments of the antigen which are then bound to class II MHC proteins and inserted into the plasma membrane
Antigen recognition
Lymphocytes respond to an antigen bound to either a class I or a class II MHC protein
What determines whether a T cell responds to antigens held in class I or class II MHC proteins?
The structure of the T cell plasma membrane: CD markers
CD3 markers
Present on all T cells
CD8 markers
Present on cytotoxic and regulatory T cells
class I MHC
CD4 markers
Present on all helper T cells
class II MHC
2 types of CD8 cells
- Responds quickly to a class I MHC-bound antigen, producing cytotoxic T cells and memory T cells
- Responds slowly, producing small number of regulatory T cells
Cytotoxic T cells
- Release perforins
- Release cytokines
- Secrete lymphotoxin
Cell mediated immunity
Results from activation of CD8 cells by antigens bound to class I MHCs T cells divide to generate cytotoxic T cells and memory T cells
Helper T cells
Respond to antigens presented by class II MHC proteins When activated, helper T cells secrete cytookines
Cytokines
Chemical messengers coordinated by the immune system
Interleukins
- Increase T cell sensitivity to antigen exposed on macrophage membranes
- Stimulate B cell activity
- Plasma cell formation, ant antibody production
- Enhance innate defenses
- Moderate immune response
Interferons (IFNs)
Slow the spread of the virus making the synthesising cell and its neighbours resistant to viral infection
Tumour necrosis factors (TFNs)
Slow tumour growth and kill tumour cells, and act as pyrogens
Colony stimulating factors (CSFs)
Factors produced by active T cells, cells of the monocyte-macrophage group, endothelial cells, and fibroblasts
B cell sensitisation
Antibody molecules in their plasma membrane bind antigens. The antigens are then displayed on the class II MHC proteins of the B cells which become activated by helper T cells activated by the same antigen
What does an active B cell differentiate into?
A plasma cell or they produce daughter cells that differentiate plasma cells and memory B cells. Antibodies are produced by plasma cells
Y-shaped antibody molecule
Consists of two parallel pairs of polypeptide chains containing constant and variable segments
Classes of immunoglobulins
- IgG
- IgE
- IgD
- IgM
- IgA
IgG
Responsible for resistance against many viruses, bacteria, bacterial toxins
IgE
Releases chemicals that accelerate local inflammation
IgD
Located on the surfaces of B cells
IgM
First type of antibody secreted after an antigen arrives
IgA
Found in glandular secretions
Antigen-antibody complex
When antibody molecules bind to an antigen
Neutralisation
Antibody binding that prevents viruses or bacterial toxins from binding to body cells
Precipitation
Forming of an insoluble immune complex
Aggltiniation
Formation of large complexes
Primary response
Antibodies first produced by plasma cells in humoral immunity
Secondary response
Maximum antibody level after second exposure to antigen
Immunocompetence
The ability to produce an immune response after exposure to an antigen
Hypersensitivites
Allergies, excessive immune responses to allergens
4 types of allergies
- Immediate hypersensitivity
- Cytotoxic reactions
- Immune complex disorders
- Delayed hypersensitivity
Anaphalaxis
When a circulating allergen affects mast cells throughout the body
Autoimmune disorders
Develop when an immune response inappropriately targets normal body cells and tissues
Immunodeficiency disease
The immune system does not develop normally or the immune response is blocked
