Immunology

Question 1

Isolated Lymphoid Follicles

Answer 1

A single follicle consisting solely of B-cells with an overlying M-cell

*Differs from Peyer’s patches because these are also found in the colon

Question 2

Effector Cells in the GALT

Answer 2

B-cells from Peyer’s Patch: Travel thru efferent lymphatic to mesenteric lymph nodes, into the blood stream, and back into the GI mucose

T-cells from Mesenteric Lymph Node: Leave and travel to gastric mucosa

Question 3

Effect B/T-cell Homing

Answer 3

1. Effector lymphocytes express a4:B7 which will bind to MADCAM-1 on the endothelial cells of gastric vasculature
2. CCL25 secreted by the SI epithelium binds to CCR9 on effector lymphs causing them to move into the lamina propria
3. IELs express aE:B7 which binds to E-cadherin expressed by SI epithelium facilitating the movement of IELs

Question 4

Isotype switching to IgA

Answer 4

TGF-B

Question 5

Functions of secretory IgA

Answer 5

1. Export toxins in the lamina propria
2. Neutralize toxins in endosomes
3. Bind Ag on mucosal surface

Question 6

Oral Immunization

Answer 6

=> IgA in GI tract (until colon) AND Mammary glands

Question 7

Intranasal Vaccination

Answer 7

=> IgA in upper respiratory tract AND cervical-vagina mucosa

Question 8

Cells of mucosal epithelia

Answer 8

CD8+ T-cells

*Activated effector cells predominate

Question 9

Gut Tolerance

Answer 9

Refers to the primary fnxn of immune cells in the GALT to restrain and not constantly activate the immune response

Question 10

CCR7

Answer 10

Molecule lost by naive T-cells when activated by Ag in the MALT; replace it w/ L-selectin

Question 11

Paneth Cells

Answer 11

Found at the crypts of the small intestinal villi and secrete antimicrobial proteins

Question 12

Best response to intracellular bacteria

Answer 12

CD4+ Th1-mediated => binds to macrophages inducing heightened ROS species formation, release of inflammatory cytokines, and increased B7 expression

*Innate response includes NK (IFN-y) activation of macs

Question 13

Best Mechanism for Viral Defense

Answer 13

CD8+ mediated elimination of effected cells thru the release of perforins/granzymes and the binding of Fas-FasL

*Ab response is important before the virus is intracellular and after its release

Question 14

Best response for Extracellular Pathogens

Answer 14

Mediated by Abs released from CD4+-Th2 cells; release Abs into the bloodstream from the lymph node that fnxn to:

1. Activate the classical complement pathway => Anaphylaxis, complement coating
2. Bind Ag and macrophages thru the FcR-y
3. Opsonization of bacteria
   * CD4+-Th1 cells will also release IFN-y and TNF-a

Question 15

Adaptive Immune Response to Protozoa

Answer 15

Intracellular => Cell-mediated immunity via Th1 activation of macrophages by IFN-y release

Extracellular => Ab release triggering lysis, opsonization, and complement activation

Question 16

Adaptive Immune Response to Helminths

Answer 16

Mediated by CD4+-Th2 cells AND unique products released by CD4+-Th1 cells including:

1. IL-4- promotes isotypic switch to IgE

2 IL-5- activates eosinophils => release of MBP which kills parasites

3. IL-13- promotes the alternative activation of macrophages (will now compromise helminth vitality w/ granuloma formation) and increased epithelial mucous production

Question 17

Best Response to Fungal Infection

Answer 17

Mediated by CD4+-Th1 cells: Activates innate immune responses

• Treg limits response to prevent collateral damage
• Th2 can limit the response leading to fungal persistence

Question 18

Sialic Acid Residues

Answer 18

Present on the capsules of extracellular bacteria and inhibits complement activation via the alternative pathway

Question 19

lkB

Answer 19

When bound, inhibits NfkB from activating transcriptional changes; some bacteria can promote IkB binding to inhibit host response

Question 20

Septic Shock

Answer 20

Caused by the widespread activation of complement and release of IL-1, IL-12, and TNF-a

*Characterized by circulatory collapse and DIC

Question 21

Antigenic Drift

Answer 21

Gradual mutations that occur to increase the virulence factors of viral antigens

E.g-drift in the hemagglutinin gene

Question 22

Antigenic Shift

Answer 22

RNA segments are exchanged with a secondary host

=>Rapid change in the form of the protein product produced by a virus

Question 23

Response to Plasmodium

Answer 23

Sporozites exist in the blood stream => Elimination by complement

Sporozoites infect liver cells => Eliminated by CD8+ T-cells

Merozoites exist in blood => Elimination by antibodies

Question 24

Response to Leishmania

Answer 24

Exist largely in macrophages and can cause scarring and tissue damage

=>Response mediated by Th1

Question 25

Overreaction to Parasites

Answer 25

• Can result in nephrotic syndrome due to deposition of immune complexes
• Cross-recognition of peripheral nerve tissue
• Hepatosplenomegaly

Question 26

Long IgA1

Answer 26

Flexible, but susceptible to cleavage

Opposite for IgA2

Question 27

Dendritic Cells in the absence of extracellular bacterial infxn

Answer 27

Secrete TGF-B which causes FoxP3 to be expressed in CD4+ cells turning them into Treg cells

Question 28

Dendritic cells in early bacterial infection

Answer 28

Produce IL-6 which causes CD4+ cells to express RORyt causing CD4+ cells to become Th17 cells

Question 29

PPARy

Answer 29

Protein that removes NFkB from the nucleus; can be activated by bacteria as a defense mechanism

Question 30

Activators of PMNs

Answer 30

LTB4

C5a

IL-8

Bacterial peptides