Cells & Tissues of Immune System

Question 1

All immune cells are derived from ____ as a fetus, but then ___ at 7 months.

But the innate immune system is derived from a ___ progenitor and consists of ____

And the adaptive immune system is derived from a ___ projgenitor and consists of

Answer 1

Fetal liver & spleen, but then pluripotent hematopoietic stem cells in bone marrow

Innate - myeloid progenitor; neutrophils, eosinophils, basophils, mast cells, macrophages

Adaptive immune system - lymphoid progenitor; B & T cells

Question 2

B cells mature in the ___

T cells mature in the ___

Answer 2

B cells mature in the bone marrow (where all immune cells originate)

T cells go mature in the thymus

Question 3

What happens in secondary lymphoid organs like lymph nodes and spleen?

Answer 3

Lymph nodes: B & T cells in lymph meet and get activated

Spleen: B & T cells in blood meet and get activated

Mucosal lymphoid organs - tonsils, adenoids, Peyer’s patches

Question 4

Name the cell:

Produces antibodies

Cytotoxic and helper functions

Answer 4

Small lymphocyte

B cell

T Cell

Question 5

Name the cell:

Activates T cells

Initiates adaptive immune responses

Answer 5

Question 6

Name the cell:

Fully differentiated form of B cell that secretes antibodies

Answer 6

Question 7

Name the cell:

Expels parasites from the body byer leasing histamine and other active agents

Answer 7

Question 8

Name the cell:

Kills cells infected w certain viruses

Answer 8

Question 9

Name the cell:

circulator precursor cell to a macrophage

Answer 9

Question 10

Name the cell:

phagocytosis and killing microorganisms

Answer 10

Neutrophils make up the majority of leukocytes!

Question 11

Name the cell:

Phagocytosis & killing microorganisms

Activation of T cells and initiation of immune response

Answer 11

Question 12

What cell…

• Kills antibody coated parasites through release of granule contents?
• Controls immune responses to parasites?
• Is involved in platelet formation, wound repair?

Answer 12

Question 13

Lymphocyte maturation (B cell in bone marrow, T cellin thymus) is antigen-independent.

What happens in lymphocyte maturation in BOTH T and B cells?

Answer 13

• Acquire antigen-specific cell surface receptors
• Elimination of auto-reactive lymphocytes, especially T cells
  
  • If they aren’t killed, then –> autoimmunity

Question 14

T cell maturation

Answer 14

1. Immature T cell interacts with cortical thymic hormones (thymosin, thymulin, thymopoietin)
2. Acquires a T cell receptor (TCR) heterodimers (mostly TCR aB)
   
   1. CD3 is the signaling component of TCR
3. Establish a phenotype
   
   1. At first cells have neither: CD4-, CD8-
   2. Then, they get both: CD4+, CD8+
   3. Then, one gets turned off: CD4 for helper, CD8 for cytotoxic
4. Recognize the processed antigen presented by APCs on an MHC

Question 15

B cell maturation

(not in lecture)

Answer 15

1. Acquire B cell receptor: IgM
   
   1. (This receptor is the same antibody that the B cell is going to secrete when activated)
2. Recognize and bind the native (unprocessed) antigen
3. Clonal proliferation creates memory cells & plasma cells

Question 16

Lymphocyte activation is antigen-depedent

Answer 16

B cells recognize native antigens

T cells recognized processed antigens presented by APCs as peptide fragments guided by MHC

–> Recognition leads to clonal proliferation

Question 17

Lymphocyte recirculation

Answer 17

• Enter lymph nodes via endothelial vein
• Exit efferent lymphatics, enter afferent lymphatics to go to next node in the chain (sampling them)
• Reenter circulation via thoracic duct

Question 18

Lymph node: filters lymphs, supported by reticular network of __ and ___.

B cells are located in the ___

T cells located in the ___

Plasma cells migrat eto the __ to secrete antibodies

Answer 18

Supported by follicular dendritic cells and macrophages.

B cells - cortex

T cells- paracortex

Plasma cells go to the medulla to secrete antibodies

Question 19

_____ pushes lymph nodes through vessels

___ prevent back flow

___ and ___ can crawl into lymph nodes

Answer 19

Muscle contraction pushes lymph through vessels

Valves prevent backflow

Macrophages & hematopoietic dendritic cells can crawl into lymph nodes to present pathogens to T cells –> clonal proliferation –> new cells and antibodies exit via efferent lymphatic vessel

Question 20

Two types of dendritic cells:

Answer 20

Follicular dendriic cells: stroma cells in the B cell zones

Hematopoietic cells: immune cells in the T cell zone

Question 21

All antibodies start as ___, then antibody class switching occurs in the ___ of a lymph node.

Answer 21

Start as IgM

Class siwtching in the apical light zone of the germinal center

Question 23

The spleen filters blood.

Red pulp vs white pulp

Answer 23

• RED PULP (sinuses & cords) - non immunologic
  
  • Removes cellular debris (effete)
  • Convert hemoglobin to bilirubin
  • Release iron into circulation for reutilization
• WHITE PULP - immunologic
  
  • T cells packed around a central arteriole, forming the periarteriolar lymphoid sheath (PALS)
  • B cells organized into primary and secondary follicles, producing antibodies (IgM)

Question 24

Name some lymphoid tissues

Answer 24

Gut-associated lymphoid tissue (GALT)

Bronchus-associated lymphoid tissue (BALT)

Epithelium has cytotoxic T cells

Lamina propria has immune cells

Question 25

Peyers patches are in \_\_ What is the function of the M cells that cover them?

Answer 25

GALT ## Footnote **M cells** pass antigens to a dendritic cell to activate T cells Has more B cells than T cells to produce a lot of **IgA**

Question 26

Answer 26

B cells and plasma cells

Question 27

Answer 27

B

Question 28

4. Which of the following statements is incorrect? ## Footnote a) The spleen collects antigens from the blood b) The lymph nodes collect antigens from the skin c) The spleen is a secondary lymphoid tissue d) The spleen collects antigens from the skin e) The lymph nodes are secondary lymphoid tissues

Answer 28

D

Question 29

5. Lymphocytes enter lymph nodes by several different routes. Circulating lymphocytes may pass into the node through high-endothelial venules. What is another method by which lymphocytes migrate into lymph nodes? a) . Lymphocytes enter via the afferent lymphatic vessels. b) B cells are transcytosed across the epithelium in the GI tract. c) T cells are pinocytosed by M cells in the Peyer’s patches. d) Lymphocytes enter via the efferent lymphatic vessels

Answer 29

A

Question 30

6. Lymph nodes are compartmentalized into a cortex, paracortex, and a medulla. Which cells would typically be found along the medullary cords? a) Follicular dendritic cells b) Plasma cells c) B cells d) T cells

Answer 30

Plasma cells

Question 31

The spleen is effective against bacteria involved in Gram-negative septicemia. Why is this organ so effective against such bacterial infections?

Answer 31

IgM is produced quickly against lipopolysaccharide.