Anatomy of the immune system

Question 1

Lymphoid organs are divided into primary/central lymphoid organs and secondary/peripheral lymphoid organs. Describe the difference and give examples.

Answer 1

• immune cells are generated in central lymphoid organs (bone marrow, thymus, fetal liver)
• immune responses are initiated in peripheral lymphoid organs (spleen, LNs, MALT aka Peyer’s patches and appendix)

Question 2

Give the 7 types of innate leukocytes and functions

Answer 2

1. neutrophil: engulfs and kills extracellular pathogens
2. monocyte: precursor to tissue macrophage
3. macrophage:
4. basophil
5. eosinophil: parasite protection
6. dendritic cell
7. natural killer cell: kills tumor cells and certain virus-infected cells

Question 3

2 major types of T cells and their functions

Answer 3

• CD4+: helper T cells that help B cells class switch and help CTLs become killer cells
• CD8+: cytotoxic T cells that kill virus infected host cells

Question 4

Hematopoiesis is regulated by what?

Answer 4

-lineage-affiliated cytokines

Question 5

The major lymphatic vessels and collections of lymph nodes are arranged in series. Antigens are captures from a site of infection by ___________ which move to lymphatics and to the draining lymph node. Where are immune responses initiated?

Answer 5

• macrophages and dendritic cells

- draining lymph nodes and or the spleen

Question 6

2 ways fluids and cells can enter a lymph node; how do cells exit a LN?

Answer 6

1. they drain from skin or other peripheral locations and enter via the afferent lymphatic vessel
2. leukocytes in blood enter via High Endothelial Venules (HEVs)
   - cells exit LN via efferent lymphatic vessel

Question 7

What are the T cell and B cell zones of a lymph node called?

Answer 7

• B cell: follicle

- T cell: cortical region (paracortex)

Question 8

Resting lymphocytes enter lymph nodes mainly via ________________________. How do they reach B/T cell zones of the lymph node?

Answer 8

• High Endothelial Venules (HEV)
• lymphocytes express surface receptors which bind to ligands on HEVs and allow entry into B/T cell zones of the lymph node

Question 9

Describe the morphology of the spleen: be sure to include “pulps” in your beginning answer.

Answer 9

-The spleen can first be organized into red pulp and white pulp; red pulp is composed of vascular sinusoids filled with RBC, macrophages, and DCs. The white pulp is made up of T and B cell zones (Periarteriolar lymphoid sheath-PALS for T cells and follicles for B cells)

Question 10

Where is the site of phagocytosis of opsonized bacteria?

Answer 10

-spleen

Question 11

Individuals without a spleen are susceptible to what type of infections?

Answer 11

-encapsulated bacteria like pneumococcus and meningococcus

Question 12

3 sites of lymphocytes within the mucosal immune system of the intestine.

Answer 12

1. Peyer’s patches (mostly B cells)
2. lamina propria
3. intraepithelial collections which are mainly T cells

Question 13

What lies above the Peyer’s patch? Describe what happens with exposure to oral antigens.

Answer 13

-M cells: they internalize antigens which are delivered into Peyer’s patches; oral exposure to antigens induced B cells in the mucosal immune system to make IgA antibodies

Question 14

__________ captures antigen from epithelium and connective tissue, while blood-borne antigens are captured by APCs in the ___________.

Answer 14

• lymph nodes

- spleen

Question 15

Lymphocutes gain entry to LNs by binding to HEVs. This process is mediated by ________ on lymphocytes which bind to ligands on the HEV.

Answer 15

-L-selectins

Question 16

What is CD3 and CD19 a marker for?

Answer 16

• CD3 is a T cell marker

- CD19 is B cell marker

Question 17

The basic structure of surface Ig molecules on B cells is a monomer of an antibody, except that the heavy chain of BCRs has a _____________. The BCRs on the most naive B cells are _________.

Answer 17

• transmembrane domain

- IgM and IgD