Post on 26-Dec-2015
Lymphatic System and Immunity
Nestor T. Hilvano, M.D., M.P.H.
Learning Objectives1. Describe the components and functions of the lymphatic
system. 2. Discuss the cells involved in the lymphatic system. 3. Describe the lymphatic tissues and organs as to structure
and functions. 4. Differentiate the body’s nonspecific and specific defenses.
5. Identify the forms and properties of immunity. 6. Distinguish between cellular immunity and humoral
immunity.7. Describe the structure of an antibody and discuss the
types of antibodies.8. Explain the primary and secondary responses to antigen
exposure.9. Discuss briefly autoimmune disorders, immunodeficiency
diseases, and allergies and give examples of each type.
Lymphatic System • Components
____ - clear colorless fluid similar to plasma, no cells except lymphocytes
____ - carry lymph from peripheral tissues to veins
____- are distributed throughout the body • Functions: Immunity, Lipid absorption (lacteals in SI),
Fluid recoverya. Lymphatic tissues & organs
b. Lymph
c. Lymphatic vessels
Lymphatic Capillaries
• Closed at one end
• thinner wall, larger diameter, flat or irregular in section
• Endothelial cells loosely overlapped - allow fluid, bacteria, viruses and cells entrance
- creates valve-like flaps (prevent return to ICS)
Route of Lymph Flow• Collecting vessels: course through many lymph
nodes• Lymphatic trunks empty into 2 Collecting vessels:
a) Rt. Lymphatic duct - drain the right side of head, neck, UE, and thorax
b) Thoracic duct - drain the rest of the body * cisterna chyli – expanded, saclike chamber
• What condition results from blockage of lymphatic drainage from a limb?
a. lymphadenopathy b. lymphedema c. lymphoma d. sarcoma
Cells of Lymphatic System• Circulating Lymphocytes, 3 types
a) ____ - natural killer cells, 5% to 10% of circulating lymphocytes, responsible for immune surveillance; attack foreign cells, virus cells, and cancer cells.
b) ____ - Thymus- dependent, 80%, 3 main types: cytotoxic, suppressor, helper; CMI
c) ____ - bone marrow- derived, 10% to 15%, differentiate into plasma cell, HI • Antigen Presenting Cells (APC) – macrophages in
epidermis, mucous membrane, and lymphatic organs
a. B cell b. T cell c. NK cell d. APC cell
Structures of Body Defenses• Lymphatic tissues – unencapsulated
a) MALT (GALT) – diffuse LT
b) Lymphatic nodules– has central, pale zone called germinal center- clusters found in ileum (called Peyer’s patches) and
appendix (aggregated lymphatic nodules) • Lymphatic organs - encapsulated
– Thymus– Red BM– Spleen– Lymph nodes– Tonsils
Thymus• Located in the mediastinum; primary lymphoid
organ • Atrophies after puberty • Functions: Cellular Immune Response• Septa divides Thymic lobes into lobules containing
an outer, thymic cortex and inner, thymic medulla• Reticular epithelial cells in cortex maintain blood –
thymus barrier. • Hassall's bodies (thymic corpuscles) – acidophilic
mass located in thymic medulla.
Lymph Node• Filters lymph (removes debris, pathogens,
antigens)
• Widely distributed lymphoid organs
• Subdivided into cortex and medulla
* germinal centers for B cell activation
• _______ - enlargement of lymph nodes
• Common site for metastatic cancer
Spleen• Located at left hypochondriac
• Structures made up of:
– Red pulp: sinuses filled with erythrocytes
– White pulp: resembles lymphoid nodules
• Functions – removal of RBC/blood components, storage of iron recycled from RBC, and immune response
Tonsils• Pathogens get into tonsillar crypts and
encounter lymphocytes
• ______ tonsils = posterior inferior margin of oral cavity
• ______ tonsils = base of tongue
• ______ tonsil = lie in the nasopharynx; also called the adenoid
a. lingual b. pharyngeal (nasopharyngeal) c. palatine
Defenses Against Pathogens• Nonspecific defenses - no prior exposure,
against any type of invading agent– physical barriers – phagocytic cells – immunological surveillance– fever– Interferon (produce antiviral proteins and
destruction of cancer cells)– complement– inflammation
Complement System• Proteins that complement antibody action• Classical pathway – fast method, C1 binds to
antibody molecule attached to antigen• Alternate pathway – slow method, exposed to
antigen, with factor P, B, and D• Both split C3 into C3a and C3b
- stimulation of inflammation, attraction and enhancement of phagocytes, and cytolysis.
Inflammation• Defensive response to tissue injury
1.limits spread and destroy pathogens
2.removes debris
3.initiates tissue repair
• Cardinal signs- rubor: _________ - tumor: ________
- calor: _________ - dolor: _________
a. pain b. redness c. swelling d. warm (hot)
Specific Immunity• Properties of immunity: specificity,
versatility, tolerance and memory• 2 types of specific immunity:
cellular and humoral• ___ – complex molecules that trigger
an immune response• ___ – protein molecules that fight
against an invaders a. Antibody (immunoglobulins) b. antigen
Active and Passive Immunity• ____- Natural active immunity
– develops as a result of natural exposure to antigen
• ____- Artificial active immunity – develops after administration of antigen to prevent
disease
• ____- Natural passive immunity – acquires antibodies from mother
• ____- Artificial passive immunity – conferred by administration of antibodies
a. DPT vaccination of children b. Injection of antirabies immunoglobulins c. Immunity conferred after recovery from pulmonary tuberculosisd. Maternal antibodies transferred to infants at birth
Comparison of B and T Cells
Antigen-Presenting Cells• Function depends on MHC proteins (membrane
glycoprotein)
– act as cell ID tag• Specialized cells responsible for activating
T cell defenses• Include all the phagocytic cells. • Antigen bound to MHC proteins – activates
immune system to destroy abnormal cell or dangerous antigen
Cellular Immunity
• T cells• 3 stages – antigen recognition, attack, and
memory• CD8 = cytotoxic T and suppressor T cells• CD4 = helper T cells• Memory T cells • Organ transplant problem = ___________
Humoral Immunity• Recognition
– B cell receptors bind antigen, take in and digest antigen then display epitopes on its MHC-II protein
– After co-stimulation by TH cell, divide repeatedly, differentiate into plasma cell, produce ____________ specific to that antigen
• Attack– antibody bind to antigen, render it harmless,
‘tag it’ for destruction• Memory
– some B cells differentiate into memory cells
Antibody Structure
• Ag binding site = free tips of variable segments
• variables = confer specificity of an antibody
• constant = form the base of the antibody; basis of classification of antibodies
Antibody Classes• IgA: monomer in plasma; dimer in secretions
• IgD: monomer; B cell membrane Ag receptor
• IgE: monomer; on mast cells and basophils;
stimulates release of ________________;
important in immediate hypersensitivity.
• IgG: monomer; 80% circulating, crosses placenta, 2 immune response
• IgM: pentamer, 10% in plasma, 1 immune
response, agglutination of ABO blood group,
complement fixation
Humoral Immunity - Attack• Neutralization
– antibodies mask pathogenic region of antigen
• Complement fixation– antigen binds to IgM or IgG, antibody changes shape,
initiates complement binding
• Agglutination– antibody binds to multiple enemy cells immobilizing
them forming large complexes.
• Precipitation– creates antigen-antibody complex that precipitates
Humoral Immunity Responses
• _______ response – peak response takes 2 weeks to develop, decline rapidly
• _______ response – activates memory B cells, IgG rises quickly
a. Primary responseb. Secondary response
Hypersensitivity (Allergy)• Type I – immediate hypersensitivity; Antibody mediated = IgE
* allergic rhinitis; asthma; anaphylaxis• Type II – cytotoxic reactions, Antibody mediated
(IgG, IgM) * binds to antigens on cells; complement
activation and lyses or opsonization • Type III – Immune complex, Antibody mediated
(IgG, IgM) * complexes precipitate and trigger inflammation
• Type IV – delayed hypersensitivity, Cell mediated* 12 to 72 hour delay
Immune Disorders
• Autoimmune diseases = production of autoantibodies; RA, IDDM, thyroiditis
• Immunodeficiency diseases = SCID, HIV, or exposure to immunosuppressive agents
- HIV transmission: ________________
- Undamaged latex condom is an effective
barrier to HIV
Homework (Self-Review) 1. Define key terminologies: pathogen, lymphedema,
lymphadenopathy, antigen presenting cell, innate immunity, nonspecific immunity, antigen, antibody.
2. Differentiate humoral immunity and cellular immunity as to type of lymphocyte, antigen acted on, product of secretion, and mechanism of action.
3. Describe the forms of active and passive immunity by noting an example.
4. Give the function of the following: germinal center, NK cell, interferon, plasma cell, lymph node, spleen, thymus, and red bone marrow.
5. Describe the cardinal signs of inflammation and how it respond to tissue injury.