Unit 3 - Formative 3 D2 Tuesday

Front 1

Describe the structure of Peyer's patches

Back 1

Lymphoid FOLLICLES (not a node) covered by specialized epithelium (M cells)

B cells are primed here and leave via lymphatics to lamina propria (and other mucosal sites) where they mature into IgA secreting plasma cells

Front 2

What is the function of M cells?

Back 2

Specialized epithelial cells that cover Peyer's patches; transport antigens from lumen across epithelium (via M = Microfold apex) into dendritic cell rich area; delivers antigens into underlying lymphoid tissue where T and B cells are primed

Front 3

What is the role of CCR9 (chemokine receptor), A4B7 Integrin (adhesion molecule) and MAdCAM-I in lymphocyte homing to the lamina propria?

Back 3

T cells in lamina propria express CCR9 and A4B7 integrin

MAdCAM-1 expressed by blood vessels in lamina propria is a ligand for A4B7 integrin

Front 4

Compare contrast intraepithelial lymphocytes (IELs) with lamina propria lymphocytes (LPLs)

Back 4

IELs: CD8+ T cells, express CD45R0+, sustain epithelial integrity by rapidly eliminating infected and damaged cells

LPLs: CD4+/CD8+ T cells, NK and plasma cells, express CD45RO +, Many roles

CD45RO+ = membrane protein which modulates lymphocyte ativation

Front 5

Which cells transport antigens across the epithelium to DCs in Peyer's patches?

Back 5

M cells

Front 6

Naive B cells in the follicles of lymphoid tissues express what immunoglobulins?

Back 6

IgM and IgD

Front 7

What class of MHC do DC use to present antigenic peptides to CD4+ B cells

Back 7

MHC II

Front 8

Where is IgA dominantly produced?

Back 8

Mucosal sites; i.e. lamina propria

Front 9

What is the structure and function of IgA?

Back 9

IgA dimer exists but mostly monomeric in serum

Neutralizing antibody (neutralizes microbes/toxins); NOT an opsonizing Ab, does NOT bind/mediate lysis by complement

Front 10

What is the function of the secretory component of pIgR?

Back 10

Stays attached to IgA after release into the lumen and protects it from proteolysis

Front 11

What is the name of IgA with secretory component attached?

Back 11

sIgA/secretory IgA

Front 12

Which receptor mediates the transport of dimeric IgA across mucosal membranes?

Back 12

pIgR (polymeric immunoglobulin receptor)

Front 13

What is the difference between the inactivated polio vaccine and the oral polio vaccine?

Back 13

IPV: killed polio, injected subcutaneously, LOW LEVELS of viral sIgA
OPV: live, orally, INDUCES sIgA BINDS VIRAL SURFACE ANTIGENS PREVENTS ATTACHMENT TO MUCOSAL CELLS; REMOVED BY PERISTALSIS

Prevents virus from entering cells

Front 14

What is the difference in risk between IPV And OPV?

Back 14

Since OPV is a live (3 attenuates strains) virus can revert to virulence

Front 15

What is the rationale for oral administration of rotavirus vacine (or OPV)?

Back 15

Induces productoin of sIgA which neutralizes virus at point of entry/prevents infection
Mimics virus's fecal-oral route of transmission

Front 16

A patient presents with diarrhea. Labs reveal absent B cells and all serum Igs are low. Disorder?

Back 16

X linked agammaglobulinemia (Bruton's disease); due to a defect in B cell Tyrosine Kinase (BTK)

Front 17

A patient presents with diarrhea. You note the presence of many B cells that will not mature; all serum Igs are low

Back 17

Common Variable Immunodeficiency Disorder (CVID) can be due to giardia infection

Front 18

A patient presents with diarrhea. B cells are present; low serum IgA, IgG; HIGH serum IgM

Back 18

Hyper-IgM syndrome due to CD40L deficiency (so B cells can't be activated to produce IgA or G)

Commonly due to enteric infection

Front 19

A patient presents with diarrhea. T cells and NK cells are absent but B cells are present.

Back 19

SCID

Front 20

If lymphocytes were isolated from the lamina propria, which lymphocyte types would be highest?

Back 20

T lymphocytes expressing CCR9

Front 21

What is the difference between food poisoning and food intoxication?

Back 21

Food poisoning = microorganism ingested, replicates in GI tract, symptoms associated with toxins or virulence factors

Food intoxication; toxins in food produced by bacteria but organism not necessarily in food; symptoms APPEAR SOONER than food poisoning

Front 22

A patient presents with fever, headache, followed by half a day of abdominal cramps and a bloody, loose diarrhea. History is notable for eating chicken (poultry) and drinking unpasteurized milk. Labs show a gram negative, curved motile rod. What is the likely orgainsm?

Back 22

campylobacter jejuni; most common cause of gastroenteritis in the US

Front 23

A patient presents with bilateral crnial nerve palsias (diplopia) and difficulty swallowing (dysphagia). The patient is also notable for constipation. The patient notes consuming canned vegetables today. What is the likely organism?

Back 23

Clostridium botulinum; spores float through air and land on food which is then canned; respiratory paralysis can become severe if not fatal

Front 24

An infant presents with floppy baby syndrome and constipation for the past few days. The mother notes the infant got their hand into a honey jar earlier that week. What is the likely orgainsm?

Back 24

Clostridium botulinum; good prognosis

Front 25

What is the mechanism of action of botulinum toxin?

Back 25

A-B toxin; A subunit inactivates proteins necessary for acetylcholine release; B subunit needed for receptor binding in neurons

Stops acetylcholine from being released

Front 26

What is the major toxin of C. perfringens regarding food poisoning from contaminated meat?

Back 26

Type A; the enterotoxin disrupts ion transport in the ileum leading to fluid loss

Front 27

What is the major toxin of C. perfringens regarding necrotizing enteritis?

Back 27

Type C - the beta toxin is pore forming and causes bloody diarrhea; necrotizing inflammation of the small bowel

Front 28

A patient has been on the broad spectrum antibiotic Clindamycin and develops severe bloody diarrhea, abdominal cramping and fever. What is the likely organism?

Back 28

Clostridium difficile

Front 29

How does antibiotic use lead to diarrhea indirectly?

Back 29

Broad spectrum antibiotics kills off normal flora allowing for oppotunistic pathogens to infect

Candida albicans and clostridium difficile are two examples

Front 30

What is the mechanism of action of Toxin A for C. difficile?

Back 30

attracts neurotrphils to ileum via cytokine release and causes disruption of cell junctions, resulting in fluid movement into lumen and diarrhea

Front 31

What is the mechanism of action of Toxin B for C. difficile?

Back 31

Toxin B causes actin depolymerization and thus cytoskeletal damage it is 1000x more potent than Toxin A

Front 32

What are two common complications of listeria monocytogenes infection?

Back 32

Septicemia and meningitis

Not the most common cause of food poisoning but has the highest mortality rate

Front 33

What are the most common food sources associated with listeria monocytogenes?

Back 33

Soft cheese!

Not the most common cause of food poisoning but has the highest mortality rate

Front 34

What is the major source of Vibrio cholerae infection?

Back 34

Contaminated water; NOT usually spread person to person

Front 35

What is the primary means of treatment for Vibrio cholerae infection?

Back 35

Fluid and electrolye replacement; doxycycline

Front 36

What are the two biotypes of vibrio cholerae?

Back 36

O1 serogroup are divided into classical and El Tor

Front 37

Mechanism of action of cholera toxin?

Back 37

Vibrio cholerae synthesizes cholera toxin -> B subunit binds to epithelial cell which endocytoses A subunit; A subunit ribosylates G protein which constitutively activates adenylate cyclase; increased cAMP activates PKA through phosphorylates CFTR promotes water and Cl loss through channel

Front 38

What is the mechanism of transmission of S. aureus associated food intoxication?

Back 38

Heat stable enterotoxin; bacteria might be present if food was not heated or cooked

potato salad!

Front 39

What is the heat characteristic of the emetic vs the diarrheal form of bacillus cereus?

Back 39

Emetic: Heat stable

Diarrheal: Heat labile

Front 40

A 3 month old female infant was brought to the EM with a history of constipation to which her mother had given a tablespoon of honey for treatment. The physical exam revealed dry mucosa, sluggish pupillary response, and significant hypotonia. Gram stain of the fecal sample revealed a gram positive spore forming rod. Diagnosis?

Back 40

C. botulinum

Front 41

A 67 yo man presents with fever, abdominal cramping and frequent diarrhea for four days. He had been on the broad spectrum antibiotic clindamycin three weeks earlier. Diagnosis?

Back 41

C. difficile

Front 42

24 people became ill within 3 hrs after eating a meal at an office party. Al had nausea, vomiting and crampy abdominal pain. The food preparer had served cold ham. Which toxin would likely be identified in the ham?

Back 42

Toxin A via C. perfringens