Lymphatic & Immune Systems

Lymphatic pathways & capillaries

Lymphatic trunks and ducts

Asymmetrical!

Edema24 liters of lymph are pushed from capillaries every day to bathe the cells – if it isn’t all collected – it’s edema!!

Post-mastectomy lymphedema ------>

What is lymph?

• It is plasma• It is interstitial fluid• It is fluid picked up by lymph capillaries• It depends where it is!!

What does lymph do?

• Collects fluid and proteins that squeeze out through the capillaries

• Absorbs dietary fats• Transports bacteria and

viruses to lymph nodes

Keep it moving

• No heart• Skeletal muscle movement• Valves prevent backflow• Trunks contract a little• Inhaling creates pressure that moves lymph

from abdominal to thoracic cavity

Lymph nodes

• Bean shaped • 2.5 cm long• Medulla has T cells and

macrophages• One exit slows traffic

Lymphoid organs

• Do NOT filter lymph, but play a role– Tonsils (MALT)– Peyer’s patches (MALT)– Thymus gland– Spleen

MALT = mucosa-associated lymphatic tissue

Spleen & Thymus

• Spleen – filters blood– White pulp contains

lymphocytes– Red pulp filters out

broken down RBC’s

• Thymus – contains lymphocytes that mature in T lymphocytes

2 Lines of Defense• Innate

– Species resistance– Mechanical barriers– Chemical barriers

• Tears• Stomach acid• Salt• Antimicrobials

– Fever– Natural Killer Cells– Inflammation– Phagocytosis

• Adaptive– Antingens (sprinkles)– Antigen-presenting cells– T cells – Cytotoxic T cells (fight cancer)– Memory T cells– Helper T cells (stimulate B cells)– B cells

Immunoglobins = antibodies

What’s the diff?

T cells• Directly attack cells w/ toxins or

growth inhibitor• Mature in the thymus gland• Activated by antigen-presenting

cells• Helper T cells are targeted by HIV• Cytotoxic T cells target tumors

and virus infected cells• Memory T cells confer immunity• Activate B cells

B cells• Differentiate into Plasma

cells that produce antibodies

• Activated by specific antigens or helper T cells

• Mature in the bone marrow• Part of the humoral

response

What’s the same?

• Both respond to specific antigens• We have millions of varieties of each

What do antibodies do?

• Attack– Disable them so that macrophages will get them

• Activate enzymes that attack antigens– Complement proteins

• Change the environment to stop the antigens– inflammation

Tissue Rejection

• Human Leukocyte Antigens (HLA’s) determine our tissue type

• Inherited from parents• Three groups: HLA-A,HLA-B and HLA-DR. • many different specific HLA proteins within each

of these three groups. • ¼ chance that you and a sibling are identical• http://www.stanford.edu/dept/HPS/transplant/

html/hla.html

Allergic (hypersensitivity) Reaction

• Type I (anaphylactic)– Triggered by allergens– Occurs within minutes– Overproduction of IgE

antibodies – Severe inflammation

Ex: peanut allergy

• Type IV (delayed-reaction)– Repeated exposures to

allergins– Activates T cells– T cells cause

inflammation

Ex: poison oak

Autoimmunity

• Cytotoxic T cells attack tissues of your own body

• Mistaken identity• Why?

– Improperly educated T cells?– Virus with “self markers” on it?

• Examples: rheumatoid arthritis and multiple sclerosis