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Host Defense Exam 2 > Regional and System Specific Immunology > Flashcards

Regional and System Specific Immunology Flashcards

1
Q

Osteoclasts differentiate from what stem cell?

A

Hematopoietic stem cell, through the pathway of the common myeloid progenitor

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2
Q

Osteoblasts are derived from what stem cell?

A

Mesenchymal stem cell

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3
Q

What signalling is important for the differentiation of a mesenchymal stem cell to the osteoblast?

A

Wnt

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4
Q

How does TNF alpha affect the differentiation of a preosteoblast to a mature osteoblast?

A

TNF alpha is part of the negative regulatory pathway of osteoblast maturation.

TNF-alpha —> DKK-1 –> inhibition of osteoblast maturation

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5
Q

What cells secrete osteoprotegerin?

A

Mature osteoblasts

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6
Q

What is the effect of osteoprotegerin?

A

Osteoprotegerin inhibits the maturation of osteoclasts (through competitive binding to the RANKL receptor) and protects the bone from excessive bone resorption

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7
Q

What does “RANK” stand for?

A

Receptor associated NFkappa B

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8
Q

Where is RANKL produced?

A

The preosteoblasts

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9
Q

What is the role of RANKL?

A

RANKL induces the differentiation of osteoclasts from their precursors

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10
Q

What cells express RANK?

A

Pre-osteoclasts and osteoclasts

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11
Q

What factor is secreted by osteoblasts to that promotes the survival and proliferation of osteoclasts?

A

M-CSF

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12
Q

How does low calcium lead to increased bone resorption?

A

Low Ca2+ –> release of PTH from chief cells of parathyroid –> PTH binding to osteoblasts –> release of RANKL –> induction of osteocyte differentiation in myeloid pathway

In addition, PTH binding to osteoblasts initiates the expression of M-CSF and downregulates the expression of OPG

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13
Q

What type of cytokines induce RANKL expression and promote OC differentiation?

A

Pro-inflammatory cytokines

IL-1, IL-6, IL-8, TNF-alpha and especially IL-17

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14
Q

What type of cytokines inhibit osteoclast differentiation?

A

Anti-inflammatory cytokines

IL4 and IL10

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15
Q

What is the resulting of a dominant Th1 response in and around bone?

A

INF gamma activates macrophages –> pro-clastogenic and bone resorption

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16
Q

Which cell types are the most potent OC activators?

A

Th17

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17
Q

What balance is required for the inhibition of IL-17 production?

A

Th1/Th2 response balance

18
Q

What is the role of IL-23 in rheumatoid arthritis?

A

IL-23 promotes IL-17 production by Th17 cells –> activation and proliferation of neighboring OC cells –> bone erosion and loss of joint function

19
Q

How does Denosumab work to help with rheumatoid arthritis?

A

Denosumab is a (mab) that binds to neutralize RANKL. This prevents the differentiation and proliferation of osteoclasts to prevent joint erosion

20
Q

What happens in postmenopausal women that leads to weak bones?

A

Loss of E2 —> dysregulated OPG/RANKL ratio –> increased bone resorption

(Favor RANKL and osteoclast maturation)

21
Q

Why is any stimulus that increases inflammation in adipose tissue a bad thing?

A

Because adipose tissue is the largest endocrine organ that produces a wide array of hormones that act like cytokines. White adipose tissue is critical for homeostasis

22
Q

Differentiate M1 from M2 macrophages

A

M1: pro-inflammatory
M2: anti-inflammatory

23
Q

What is osteopontin?

A

A pro-inflammatory and potent chemotactic signal for monocytes and macrophages. It is produced by macrophages in white adipose tissue

24
Q

What is resistin?

A

Adipose tissue specific- antagonist of adiponectin

25
Q

Is leptin pro or anti-inflammatory?

A

Leptin is pro-inflammatory

26
Q

Is adiponectin pro or anti-inflammatory?

A

Adiponectin is anti-inflammatory

27
Q

What are the effects of visfatin?

A

Visfatin is pro-inflammatory and pro-angiogenic

28
Q

What are the effects of macrophage inhibitory factor cytokine?

A

Macrophage inhibitory factor cytokine is TNF-like but promotes adiponectin release

29
Q

What is the ratio of pro-and anti- inflammatory adipocytokine production in normal (non-obese) white adipose tissue?

A

There is a balance, with a net- effect of slightly anti-inflammatory production

30
Q

What happens to the ratio of pro vs anti inflammatory adipocytokines in obese WAT?

A

The balance shifts to become more pro-inflammatory. Expanding fat in adipocytes triggers a very dangerous signaling problem that makes WAT very pro-inflammatory by recruiting a large number of monocytes and macrophages to it

31
Q

Which T cells are predominantly found in adipose tissue?

A

Tregs

32
Q

How do macrophages regulate adipogenesis?

A

WNT5a and TNF=like cytokine production

33
Q

How is SFPR5 affected by obesity and metabolic syndrome?

A

SFRP5 (frizzled) receptor for WNT signaling is increased in obesity and metabolic syndrome

34
Q

Name two ways adipocytes counteract the pro-inflammatory signaling by macrophages

A

1) Adipocytes secreted SFRP5 to counteract the WNT5a signaling by macrophages
2) Adipocytes secrete Adiponectin to counteract the TNF secretion by macrophages

35
Q

Why is there a net pro-inflammatory production of cytokines in obese WAT?

A

Obese WAT leads to increased macrophage infiltration. This leads to an overproduction of TNF, IL-6 and CCL2 (all pro-inflammatory) cytokines and chemokines that has a positive feedback of more pro-inflammatory responses

36
Q

What is the status of the innate immune responses is brain?

A

Innate immune responses in the brain are held in active suppression by microglia and IL-10 and TGFbeta

37
Q

What are the two different subsets of microglia in the CNS?

A

1) migrate early in development, have DC and M2 macrophage characteristics. Highly branched and display little MHC
2) Perivascular and derived from circulating monocytes

38
Q

What happens to the M2 macrophages upon infection in the brain?

A

Activation of the glial system by DAMPS/PAMPS converts the M2 to M1 and then they secrete pro-inflammatory cytokines. They upregulate their MHC and change their morphology

39
Q

Which cells of the CNS are responsible for stabilizing the pro-inflammatory positive feedback loops?

A

Neurons- through secretion of specific neurotransmitters

40
Q

Which pro-inflammatory cytokine is most important effects on neural function and survival/

A

IL-6

Host Defense Exam 2 (11 decks)

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