Ch2 Cells

Question 1

What are the primary functions of phagocytes?

Answer 1

1) Ingestion and destruction of microbes

2) Clearance of dead tissues

Question 2

What is the content of the 2 granule types in neutrophil?

Answer 2

1) Specific Granules - lysozyme, collagenase, and elastase

2) Azurophilic Granules - lysosomes containing defensins and cathelicidins

Question 3

How many neutophils are produced per day, and how long to they survive?

Answer 3

1x10^11; circulate in the blood for hours-days; in infected tissue they function for 1-2days

Question 4

What surface markers identify human and mouse classical monocytes?

Answer 4

Human: CD14++CD16-
Mouse: Ly6-high

Question 5

Which monocytes are more numerous, classical or non-classical? What is their function? What is the function of the rarer population?

Answer 5

Classical are more abundant, are rapidly required to sites of infection/injury, pro-inflammatory.
Non-classical are more rare, patrolling along endothelia, involved in tissue repair, CD14+CD16++ in humans and Ly6C-low in mice.
Intermediate population in humans also exists: CD14++CD16+

Question 6

What are the functions of tissue resident macrophages

Answer 6

1) Ingestion and killing of microbes
2) Ingestion and clearance of dead cells
3) Cytokine production - activation of endothelia for leukocyte recruitment, amplifying inflammation
4) APC for adaptive immune system
5) Angiogenesis and fibrosis - promote the repair of damaged tissues by stimulating new blood vessel growth (angiogenesis) and synthesis of collagen-rich extracellular matrix (fibrosis).

Question 7

What changes occur in macrophages after activation?

Answer 7

Depends on the kind of activation!
1) Classical - killing internalized microbes
2) Alternative - tissue repair
Spectrum in between.
Morphology can change too, i.e. epitheliod cells (macrophages with lots of cytoplasm), multi-nucleated giant cells, etc.

Question 8

Unlike neutrophils, macrophages are not terminally differentiated. How does this impact the immune response to infection?

Answer 8

Macrophages can proliferate at the site of infection and persist for days. Therefore, after the first 1-2 days they are the primary cell of the immune response.

Question 9

Where are mast cells found in the body?

Answer 9

In tissues, lining small blood vessels and nerves.
Cytoplasm contains many membrane-bound granules filled with acidic proteoglycans that bind basic dyes, as well as histamine.

Question 10

Where are basophils found in the body?

Answer 10

Usually in the circulation, rarely in tissues. Like the blood version of mast cells.

Question 11

Where are eosinophils found in the body?

Answer 11

Circulating in the blood and some are found at mucousal sites.
Contain basic proteins that bind acidic dyes such as eosin. GM-CSF, IL-3, and IL-5 promote eosinophil maturation from myeloid precursors.

Question 12

What are classical (conventional) DC?

Answer 12

DCs of the skin, mucosa, or organ parenchyma that respond to microbes by migrating to lymph nodes, where they display microbial protein antigens to T lymphocytes

Question 13

What are pDCs?

Answer 13

Plasmacytoid DC. Early responders to viral infections. Recognize nucleic acids of intracellular viruses and produce type I interferons.

Question 14

What are follicular dendritic cells?

Answer 14

Stromal cells that have a dendritic cell morphology; membranous projections that are found intermingled in collections of activated B cells in the lymphoid follicles of lymph nodes, spleen, and mucosal lymphoid tissues

Question 15

How was it discovered that lymphocytes were the mediators of humoral and cellular immunity?

Answer 15

Adoptive transfer experiments. Experiments done mainly with mice showed that protective immunity to microbes can be adoptively transferred from immunized to naive animals only by lymphocytes or their secreted products.

Question 16

How many lymphocytes are there in a human? Where are they found?

Answer 16

Total: 5x10^11
∼2% are in the blood,
∼ 4% in the skin,
∼10% in the bone marrow,
∼15% in the mucosal lymphoid tissues (GI and respiratory)
∼65% in lymphoid organs (spleen and lymph nodes)

Question 17

In what organ were B cells originally found to develop?

Answer 17

Bursa of Fabricius in chickens.

Bone marrow in humans :P

Question 18

What’s the big diff between normal B cells and MZ B cells or B-1 cells?

Answer 18

Follicular B cells express highly diverse, clonally distributed sets of antibodies that serve as cell surface antigen receptors and as the key secreted effector molecules of adaptive humoral immunity.
Marginal zone B cells and B-1 cells have antigen receptors of limited specificity.

Question 19

What does CD stand for in surface marker designations?

Answer 19

Cluster of Differentiation

Question 20

What does irradiation do to a mouse?

Answer 20

Lymphocytes and their precursors are radiosensitive and are killed by high doses of γ-irradiation - so it wipes their lymphocyte populations out. Allows transfer/reconstitution experiments in mice.

Question 21

What’s the difference between a mature and naive lymphocyte?

Answer 21

None. Mature B and T cells that haven’t encountered antigen are called naive. Naive cells are functionally quiescent, but fully developed to initiate a response (to be activated by antigen)

Question 22

Where to B cells mature? Where do T cells mature?

Answer 22

B cells mature in circulation. T cells mature in the thymus.

Question 23

List the series of steps from antigen recognition to acquisition of effector functions that occurs during T/B cell activation.

Answer 23

Protein synthesis (i.e. cytokines and their receptors) –> switch for G0 to G1 = proliferation and differentiation –> increased size of cell –> up to 50,000 cells from a single T cell; 5000 from a single B cell. Once finished diff, no more prolif.

Question 24

True or False: Naive cells are not the only kind of lymphocyte found in tissues.

Answer 24

True. Mixtures of naive, effector, and memory lymphocytes are always present in various sites throughout the body.

Question 25

What is the life span of naive T/B cells that do not meet their antigens?

Answer 25

1-3 months.

Question 26

What did experiments with mice in which the genes that encode the antigen receptors of B cells or T cells were deleted after the lymphocytes matured tell us about these cells?

Answer 26

They require survival signals to persist. Without survival signals from the antigen receptors, T/B cells die within 2-3 weeks.

Question 27

Or than TCR/BCR signaling, what other signals are required for T/B cell survival?

Answer 27

Cytokine stimulation:
IL-7 signalling for T cells
BAFF signalling for B cells.

Question 28

What is homeostatic proliferation?

Answer 28

Any loss of lymphocytes leads to a compensatory proliferation of the remaining ones and increased output from the generative organs.

Question 29

What are LTi?

Answer 29

Lymphoid tissue–inducer cells are a subset of ILCs that produce the cytokines lymphotoxin and TNF, and are essential for the formation of organized secondary lymphoid tissues.