lecture 2 exam 2

Question 1

function of secondary lymphoid tissue

Answer 1

develops late in fetal life and persists life long
facilitate antigen trapping
collects antigen presenting cells (DC) and lymphocytes
support clonal expansion of antigen specific T and B lymphocytes
antigen specific T and B cell effectors move to target tissues
retain any antigen specific memory cells

Question 2

encapsulated secondary lymphoid tissue

Answer 2

lymph nodes
spleen
hemalnodes

Question 3

unencapsulated secondary lymphoid tissue

Answer 3

mucosal lymphoid tissue (MALT)
gut associated lymphoid tissue (GALT)
bronchial associated lymphiod tissue (BALT)
tonsils

Question 4

lymph node schematic

Answer 4

T cell clonal proliferation in paracortex w CD3
B cell clonal proliferation in germinal center of follicle
Ag and APC drainage from inflamed tissue through lymph flow from cortex to medulla
blood flows opposite direction
naive cells enter the lymph node thorugh high endothelial venules

Question 5

how does antigen get to lymp node to stimulate an immune response

Answer 5

DC take up bacterial antigens in skin and then move to enter draining lymphatic vessel
DC bearing the antigen enter the draining lymph node (cortex-medulla) where they settle in T cell areas (paracortex)

Question 6

T and B effector cells & antibodies leave via

Answer 6

efferent lymphatics to thoracic duct and systemic circulation

Question 7

chemotaxis

Answer 7

movement of cell in response to chemical stimulus

Question 8

chemokine

Answer 8

a family of cytokines w ability to induce directed chemotaxis
tell cells where to go!!
migration to ln through HEV is regulated by chemokines and adhesion molecules

Question 9

integrins

Answer 9

transmembrane cell adhesion proteins and signaling receptor

migration to ln through HEV is regulated by chemokines and adhesion molecules

Question 10

high endothelial venules

Answer 10

HEV are sticky for naive lymphocytes
in paracortex of ln
L selectin on lymphocytes (CD62L) bind vascular addressins (CD34) on endothelium of HEV
rolling to diapedesis process

CD62L + CD34/glyCAM1 = loose
ICAM + LFA = tight

Question 11

how do DC arrive in paracortex

Answer 11

CCR7 - on T cell and DC attracted to CCL19 & CCL21 expressed in paracortex
CXCR4 - on DC attracted to CXCL12 in paracortex

Question 12

how do B cells get to LN follicle

Answer 12

CXCR5 - on b cell attracted to CXCL13 in follicle
CCR7 - on be cells comes through HEVS to CCL19, CCL21 paracortex

loop through lymphoid system for up to 100 days for antigen
present their antigen they encounter in T cell w MHC 2 to T cells

Question 13

cognate interaction

Answer 13

T & B recognize same antigen’s differnet epitopes

Question 14

B cell activation and differentiation

Answer 14

1. b cell activation in paracortex of lymph node (find antigen and BCR rearrangement)
2. somatic hypermutation (in follicle) in the germinal dark zone of germinal center
3. affinity maturation in germinal light zone by follicular DC
4. isotype (class) switch) in germinal light zone - either apoptosis or survivie and call Tfh cells through cytokines then become plasma or memory b cell

Question 15

phase 1: B cell activation

Answer 15

in paracortex
complete activation of B cells requires multiple signals from other sources
helper t cell co stimulation:
1. antigen specific
2. costimulation
3. cytokines

Question 16

signal 1 for B cell activation

Answer 16

antigen specific
antigen binding to BCR + CR2/CD21
-ag processed to peptide and presented to Th on MHC 2 from b cell

Question 17

signal 2 for B cell activation

Answer 17

costimulation

of CD40 on B cell + CD154 (CD40L) on T cell

Question 18

signal 3 for B cell activation

Answer 18

cytokines

IL4 made by T cell engages IL4 on B cell to signal proliferation & differentiaion

Question 19

phase 2: clonal expansion & somatic hypermutation

Answer 19

Th activated B cells move to dark zone of germinal center and proliferate
somatic hypermutation: mutational hotspots in rearranged DNA that encodes CDR1, CDR2, CDR3
-AID: activation induced cytidine deaminase ONLY made in B cells

Question 20

AID in B cells

Answer 20

activation induced cytidine deaminase
deaminates cytosines and leaves uracils during ssDNA transcription
DNA repair enzymes replace all uracils w other nucleotides randomly

activity results in altering aa sequence, protein structure, antigen affinity

Question 21

phase 3: affinity maturation

Answer 21

B cells enter light zone of germinal follicle and encounter the antigen present on FDC
newly mutated BCRs that bind to antigen w high affinity receive survival signals
BCRs that bind w low affinity do not receive survival signals so the apoptosis

Question 22

phase 4: isotype (class) switching

Answer 22

B cells w high affinity BCRs move to margin of germinal center and interact w Tfollicular helper cells for cytokines signals to cause class switching on B cell

IGNgamma cuases IgM -> IgG
IL4 causes IgM -> IgE
TGF beta causes IgM -> IgA

IL21 is essential for TFH and plasma cell differeniation

Question 23

IFNgamma cytokine signaled to B cell causes

Answer 23

IgM -> IgG

Question 24

IL4 cytokine signaled to B cell causes

Answer 24

IgM -> IgE

Question 25

TGFbeta cytokine signaled to B cell causes

Answer 25

IgM -> IgA

Question 26

how many lymphocytes are in pig lymph

Answer 26

NONE - lymph nodes are inside out

Question 27

hemolymph

Answer 27

dark red or brown most prominent in ruminants scattered among blood vessels - filter blood and substances in circulation contain B cells in cortex and T cells at center have gamma delta T cells

Question 28

spleen structure

Answer 28

red pulp white pulp encapsulated

Question 29

red pulp of spleen

Answer 29

filters blood rather than lymph removes aged blood cells and immune complex coated cells by macrophages in sinus of red pulp salvage iron and bilirubin from red cells

Question 30

white pulp of spleen

Answer 30

marginal zone - macrophages surround (APC) outer region of follicle follicles - b cell home periarteriolar sheath (PALS) - T cells NO HEV

Question 31

sinusoidal type of spleen

Answer 31

abundant venous sinuses store large amounts of blood for quick release (horses, dogs, humans) splenic contraction during physical exercise smooth muscle around ellipsoid capillary (most prominent in horses)

Question 32

nonsinusoidal type of spleen

Answer 32

poorly developed sinuses | cats and ruminant

Question 33

bone marrow as secondary lymphoid tissue

Answer 33

memory cells and plasma cells colonize | second dose of aantigen causes bone marrow to release large quantities of antibodies in rodents and other species