Lymphatic and Immune Systems

LYMPHATIC SYSTEM AND IMMUNITY

*Note: A great resource on diseases and the immune system is the Centers for Disease Control Web site at http://www.cdc.gov.

I. Introduction to the Lymphatic System

A. Functions

1. Lymphocytes

2. Tissue fluid

3. Return substances to bloodstream

B. Lymphatic pathways

1. Lymphatic capillaries

a. Closed-ended tubes

b. Lacteals -

2. Larger lymphatic vessels

a. Similar to veins

b. Lymphatic trunks

c. Lymphatic collecting ducts

1. Right lymphatic duct

2. Thoracic duct

3. Movement of Lymph

a. Milking action of skeletal muscles

b. Respiratory pump

c. Movement of adjacent tissues and pulsing action of arteries

4. Edema

C. Lymphocytes

1. T Cells

a. Cytotoxic

b. Helper T

c. Suppressor

2. B Cells

a. Plasma cells

b. Antibodies

3. NK Cells

D. Origin and Circulation of Lymphocytes

1. Lymphopoiesis occurs in bone marrow and thymus

a. One group remains in bone marrow to differentiate into NK and B cells

b. Second group migrates out of bone marrow and to thymus to become T cells

2. Lymphoid nodules (spherical clusters of lymphatic tissue including lymphocytes and macrophages)

a. Germinal center

b. Location: beneath epithelia, tonsils are lymphoid nodules

II. Lymphatic organs

A. Lymph nodes

1. Structure

a. Afferent lymphatic vessels

b. Efferent lymphatic vessels (hylus)

c. Lymphatic nodules with lymphocytes and macrophages

d. Lymphatic sinuses

e. Blood vessels

2. Location

a. Aggregate in chains along the length of lymphatic vessels

b. Predominant in cervical, axillary and inguinal regions

3. Functions of lymph nodes

a. Filter lymph

b. Lymphocytes

c. Macrophages

B. Thymus

1. Structure

a. Bilobed

b. Large in infancy

c. Lymphatic tissue subdivided by lobules

2. Location

3. Functions of the thymus

a. T lymphocytes mature here

b. Thymosins (hormones)

C. Spleen

1. Structure

a. Largest lymphatic organ

b. Resembles a large lymph node with lobules surrounded by CT capsule

c. Spaces within the lobule are filled with blood

d. White pulp

e. Red pulp

2. Location

3. Functions of the spleen

a. ________________________________

b. ________________________________

c. ________________________________

d. ________________________________

4. Removal of spleen (splenectomy)

D. Tonsils

1. Swellings of the pharyngeal mucosa

2. B cells

3. Examples:

a. Pharyngeal

b. Palatine

c. Lingual

E. Lymphatic Tissues

1. Peyers patches of the ileum

2. Appendix

3. Lymphatic nodules scattered throughout the body (mostly under epithelial tissue)

III. Body Defenses and the Lymphatic System

A. Nonspecific body defenses

1. Physical Barriers

2. Phagocytes

3. Immunological Surveillance

4. Interferons

5. Complement

6. Inflammation

7. Fever

B. Specific defenses and the Immune Response

1. Forms of Immunity

*TYPE OF IMMUNITY*	*NATURALLY ACQUIRED*	*ARTIFICIALLY ACQUIRED*
ACTIVE IMMUNITY
PASSIVE IMMUNITY

2. Properties of Immunity

a. Specificity

b. Versatility

c. Memory

d. Tolerance

4. Antigens

C. Overview of the Immune Response

1. T cells and Cell-mediated Immunity

a. MHC Proteins

b. T Cell Activation

c. Actions of T cells

i. Cytotoxic T cells recognize foreign antigens bound to Class I MHC proteins of infected cells

ii. Memory T cells

iii. Suppressor T cells

iv. Helper T cells recognize foreign antigens bound to Class II MHC proteins of Antigen-Presenting Cells (APCs)

2. B cells and Antibody-mediated Immunity

a. B cell Activation

i. Ag-receptors

ii. Activated B cell --> memory cells and plasma cells --> antibodies (~2,000/sec)

b. Memory B cells

c. Antibody Structure

i. Antigen-binding site

ii. Variable segments

iii. Constant segments

d. Classes of Antibodies

i. IgG

ii. IgM

iii. IgA

iv. IgE

v. Ig D

e. Antibody Functions (they have a PLAN of attack):

i. Precipitation

ii. Lysis

iii. Agglutination

iv. Neutralization

f. Monoclonal antibodies ("magic bullets")

III. Immune Responses

A. Primary immune response (first encounter)

1. Abs are produced for several weeks

2. Some B cells become memory cells

B. Secondary immune response (second encounter)

C. Hormones and the Immune System

1. Cytokines (classes of hormones that act as chemical messengers during the immune response)

a. Interleukins (Il) - a wide variety of proteins produced to increase T and B cell responses, promote most nonspecific defense actions such as inflammation and fever (if response is prolonged, can cause many adverse bodily effects such as rash, arthritis, pain, etc...)

b. Interferons - interfere with viral replication

c. Colony-Stimulating Factors (CSFs) - promote the division and differentiation of the blood cells, particularly all types of leukocytes

D. Autoimmune Disorders

E. Allergic (hypersensitivity) reactions

1. Type I: Immediate hypersensitivities (Ex: hay fevers, environmental exposure allergies)

2. Type II: Cytotoxic Reactions (ex.: Transfusion reactions)

3. Type III: Immune complex hypersensitivities - high levels of antigens bound to antibodies are harder to clear from the body and can lead to problems in the vascular system and kidneys (the complement system is activated in these instances leading to further complications, such as inflammation and tissue damage)

4. Type IV: Delayed hypersensitivities (Ex: poison ivy)

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Last Updated 06/08/07