110: lymphatic and immune systems

What is an antibody vs. antigen?

antigen (Ag): surface marker

antibody (Ab): protein released by plasma cell, binds specific Ag

What is the role of the lymphatic system?

produce, maintain and distribute lymphocytes

maintain net filtration pressure

How is the lymphatic system organized?

vessels (lymphatics)

fluid (lymph)

organs

What is the pathway of lymph vessels?

arteries → capillaries → interstitial space → lymphatic capillaries → vessels → trunks → ducts → venous blood

How do lymphatic capillaries compare to blood capillaries?

blind-ended

very permeable

anchor by collagen (prevent collapse)

T/F lymphatic capillaries are found in bone, bone marrow and teeth.

F

What are lacteals?

specialized lymph capillaries in small intestine

absorb fat, deliver chyle to bloodstream

What do the following drain:

a) R/L jugular trunk

b) R/L subclavian trunk

c) R/L bronchomediastinal trunk

d) intestinal trunk

e) R/L lumbar trunk

a) head/neck

b) upper limbs

c) thorax

d) intestines

e) lower limbs

What do the right lymphatic duct and thoracic duct drain?

R lymph: R body superior diaphragm

thoracic: everything inferior diaphragm and L body superior diaphragm

What are the classes of lymphocytes? They are a type of ________

T cells (majority; cytotoxic, helper, suppressor)

B cells (plasma)

NK cells (kill things that don’t belong)

leukocyte (WBC)

How do NK cells do their thang?

1. cell w/ unusual Ag activate NK

2. NK golgi produce vesicles w/ perforins

3. perforins released by exocytosis

4. form pores in target cell membrane = disintegrate

What are 3 other types of lymphoid cells?

1. macrophages: phagocytize foreign, activate T cells

2. dendritic cells: capture Ag, deliver to lymph nodes

3. reticular cells: support other cells

What is the difference between primary and secondary lymphoid organs?

primary: where B & T cells mature, ex: thymus & red bone marrow

secondary: where B & T cells encounter Ag, ex: tonsils, lymph nodes, spleen, appendix

How are lymphocytes made and activated?

1. origin red bone marrow

2. mature (T cells → thymus, B cells → bone marrow)

3. leave primary to seed secondary lymphoid organs (still naive)

4. encounter Ag and activate

5. proliferation and differentiation into effector and memory cells

What are the two stages of learning that T cells fall under?

1. + selection: recognize self (if no = apoptosis)

2. - selection: no recognize self (do not want body to attack self) (yes = apoptosis)

want to recognize self MHC (+), no recognize self Ag (-)

Do most T cells pass positive and negative selection?

no, only 1%

What are the two types of lymphoid tissue?

1. diffuse lymphatic tissue: lymphoid cells + reticular fibers, almost all organs

2. lymphoid follicles: solid sphercial bodies, germinal center (antibody production, proliferating B cells)

What are the functions of lymph nodes?

filter lymph (macrophages destroy microorganisms and debris)

activate immune system

How does lymph circulate in the lymph node?

1. lymph enters via afferent vessel (a = arriving)

2. travel large subscapular sinus and medullary sinus

3. exit hilum via efferent vessel

What is the importance of germinal centers?

provide opportunity to encounter foreign Ag to form immune response (check-point)

What is the structure of the spleen?

white pulp (lymphocytes, reticular fibers, T& B cells interact with blood)

red pulp (macrophages to remove old RBC and pathogens)

What is the function of the spleen?

lymphocyte proliferation, immune surveillance and response

cleans blood

What is the role of mucosa-associated lymphatic tissue (MALT)?

protect digestive and respiratory system from foreign matter

T/F the thymus is largest in adulthood

F, largest in childhood

What is the function of the thymus?

T cellmaturation

What is the difference between innate and adaptive defenses?

innate: present at birth, surface barrier (1st line; skin and mucous membranes) and internal defense (2nd line; phagocytes, NK cells, inflammation, fever)

adaptive: humoral (B cells) and cellular (T cells) immunity (3rd line defense, very specific)

The skin is the ____ line of defense. What does it do?

1st

maintain boundary, acid mantle (contain bactericidal chemicals), keratin

The intact mucous membrane is the ____ line of defense. What does it do?

1st

barrier prevent entry pathogens

ex: nasal hairs, mucus, gastric juice, acid vagina, lacrimal and salivary glands, urine

The internal defense is the ___ line of defense. What cells are included?

2nd

phagocytes (eat pathogens), NK cells (promote apoptosis)

What are some antimicrobial proteins involved in internal defense?

interferons (a, B, gamma): released by virus-infected cells, cell sacrifices itself to protect uninfected cells

complement: blood bourne, phagocytosis (opsonisation → make foreign substance easier to find and remove), MAC (membrane attack complex) lyse, intensify inflammation

Humoral immunity is the ___ line of defense. What is involved?

B cell + antibody = antigen-antibody complex

Cause: PLAN (precipitation, lysis, agglutination, neutralization)

ppt and agglu: group blood and cells

neutral: mask dangerous part

PAN of PLAN inactivate complex

What is the primary and secondary response for humoral immunity?

primary: Ag binds specific B cell → clone → plasma cells (secrete antibody) and memory B cell (watch & wait)

secondary: years later, memory cell triggers way more plasma cells and antibodies + memory cells

How does the magnitude and response time of 2nd time exposure compare to primary immune response?

faster and larger

Humoral immunity can be divided into active and passive and further divided into naturally and artificially acquired. Provide a description of each.

Active: need to encounter antigen

• natural: contact with pathogen

• acquired: vaccines

Passive: no memory

• natural: antibodies passed from mother to baby

• acquired: inject antibodies, ex: rabies deliver antibody immediately

What are the different classes of Ab AKA Ig made by B cells and what do they do?

IgM: 1st released, primary response

IgA: body secretions

IgD: B cell surface

IgG: most abundant, secondary and late response, cross placenta

IgE: inflammation, allergic rxn

Cellular immunity is ___ line of defense. What does it involve?

3rd

class I: recognized by CD8 and cytotoxic T cells, endogenous, APC = kill all cells with it, no APC = kill me

class II: recognized by CD4 and helper T cells, exogenous, found on APCs

How do cytotoxic T cells target cells?

1. Tc recognize foreign Ag on MHC I & bind

2. release perforin and granzyme molecules by exocytosis

3. perforin insert into cell membrane, form pores

4. granzymes enter cell and activate apoptosis

5. Tc detaches, search next target

How does the body defend against its 1st exposure to influenza virus?

1st line defense: mucus traps virus, cilia sweep mucus to pharynx

2nd line defense (non-specific): virus infected cells release interferon, phagocytes eat virus, inflammation recruits more immune cells, complement pokes holes, NK cells kill

3rd line defense: dendritic cells (APCs) engulf virus, present to lymph node to activate T cells, activate CD4 → form clone helper T cells and memory cells, release antibodies,