Lymphatic System

Lymphatic System and Immunity

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Fluid Leaves Capillary

Cells

Blood

Blood Capillary


Capillaries


Functions of Lymphatic System

• Drain fluid from around cells

• Absorb fat from intestines

• Circulate lymph

• Filter lymph

• Immunity


Right Lymphatic Duct

Thoracic Duct


Lymph

• Fluid of the lymphatic system

• Similar to blood plasma and interstitial fluid


Lymphatic Vessels

• Transport lymph

• Lymph is returned to the circulatory system at either the right or left subclavian veins


Lymph Nodes

• Filter lymph– Microorganisms

– Cancer cells

• Lymphocytes• Monocytes


Thymus

• Programs some lymphocytes to develop into T-cells


Spleen

• Filters blood– Worn out RBC– Bacteria

• Lymphocytes

• Monocytes


Fluid Movement


Edema

• Accumulation of interstitial fluid


Causes of Edema

• Blockage of lymphatic system

• Increased pressure in veins

• Lack of albumin– Decreases fluid returning to blood capillaries

by osmosis

• Inflammation


Nonspecific Body Defenses

• Skin

• Acid– Stomach– Vagina

• Mucus

• Saliva

• Tears


More Nonspecific Defenses

• Phagocytosis

• Complement

• Fever

• Inflammation


Complement


Inflammation

• Bodies response to tissue injury

• Classic signs– Heat– Redness– Swelling– Pain


Skin

Blood


Tissue Damaged


Histamine Released


Capillary More Permeable

Plasma Leaks Out



Antibodies Leaks Out



WBCs Leave by Diapedesis


Wall of Fibrin Forms


Pus Forms


Steroid Hormones

• Hydrocortisone, cortisone and others

• Depress inflammation

• Used to treat inflammatory diseases– Rheumatoid arthritis


Antigens

• Molecules often found in the membrane of cells

• Antigens of foreign cells stimulate an immune response


Self Antigens

• Antigens of our own cells

• Do not cause an immune response in our body– Usually cause an immune response in another

person

• MHC proteins– Major Histocompatibility Complex


Cells of the Immune System

• APCs– Antigen-presenting cells

• B cells– B lymphocytes

• T cells– T lymphocytes


Antigen-Presenting Cells

• Macrophages• Engulf foreign cells and attach the cells antigens on their

MHC proteins


Lymphocytes

T Cells B Cells


B Cell

Receptor

Foreign Cell


Cytotoxic T Cell = Killer T Cell

Receptor

Body Cell


Helper T Cell

Receptor

APC


Antigen-Presenting CellAPC

• Macrophages and other cells

• Engulfs and digests foreign cells

• Present antigens on MHC proteins to T cells


B Cells

• Lymphocytes that react directly with antigens

• Require stimulation from Helper T Cells

• Offspring become– Plasma cells– Memory B cells

• Humoral Immunity


Plasma Cells

• Produce huge numbers of antibodies– 2000/second


Helper T Cell

• Reacts with antigen from APC

• Stimulates Cytotoxic T Cells and B Cells– Secretes Interleukin II


Cytotoxic T Cells

• Activated by antigens on any body cell

• Require stimulation from Helper T Cells

• Destroys body cells infected with viruses

• Destroys cancer cells• Cellular Immunity


Memory Cells

• T Cells and B Cells

• Remember antigen

• React to a second invasion of an antigen more rapidly


Suppressor T Cells

• Stops T cells and B cells after an infection has been conquered


Cytokines

• Chemicals used in cellular immunity• Interleukin I

– Produced by macrophages– Stimulates helper T cells

• Interleukin II– Produced by helper T cells

• Perforin– Causes lysis of target cell


Virus

Protein Coat

DNA or RNA


Virus Attaches to Body Cell


Viral DNA Enters Host


Protein Coats Synthesized


Viral DNA Synthesized


Viruses Exit Cell


Host Cell Killed by Virus


Interferon Produced by Dying Cell


Acquired Immune Deficiency Syndrome

• HIV Virus

• Attacks and destroys Helper T Cells– Depresses humoral and cellular immunity


Lymphatic System

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