Immuno - Lymphoid Structures

Question 1

What kind of lymphoid organ is a lymph node? How many afferents versus efferents does it have?

Answer 1

A secondary lymphoid organ that has many afferents, 1 or more efferents

Question 2

What are 2 histological characteristics of a lymph node?

Answer 2

Encapsulated, with trabeculae

Question 3

What functions do lymph nodes serve?

Answer 3

Functions are (1) nonspecific filtration by macrophages, (2) storage and activation of B and T cells, (3) antibody production

Question 4

Where are lymph node follicles found? What function/purpose do they serve?

Answer 4

In outer cortex; Site of B-cell localization and proliferation

Question 5

What is the difference between primary and secondary follicles in lymph nodes?

Answer 5

PRIMARY follicles are dense and dormant, SECONDARY follicles have pale central germinal centers and are active

Question 6

Of what components does the medulla of a lymph node consist?

Answer 6

Consists of medullary cords (closely packed lymphocytes and plasma cells) and medullary sinuses

Question 7

What function/purpose do medullary sinuses of lymph nodes serve?

Answer 7

Medullary sinuses communicate with efferent lymphatics and contain reticular cells and macrophages

Question 8

Where is the paracortex of a lymph node found? What type of cells does it house?

Answer 8

Region of cortex between follicles and medulla; Houses T cells

Question 9

What kind of vessels are found in the paracortex, and what function do they serve? What implication does this have?

Answer 9

Contains high endothelial venules through which T and B cells enter from blood; In an extreme cellular immune response (i.e., viral), paracortex becomes enlarged.

Question 10

Which lymph node component is not well developed in DiGeorge syndrome?

Answer 10

Paracortex - Not well developed in patients with DiGeorge syndrome

Question 11

Draw a visual of a lymph node, labeling the following: (1) Capsule (2) Subcapsular sinus (3) Capillary supply (4) Efferent lymphatic (5) Afferent lymphatic (6) Artery (7) Vein (8) Postcapillary (high endothelial) venules (9) Follicle of cortex (B cells) (10) Paracortex (T cells) (11) Medullary sinus (macrophages) (12) Trabecula (13) Medullary cords (plasma cells).

Answer 11

See p. 192 in First Aid for visual

Question 12

Name the primary cell type associated with each of the following regions in a lymph node: (1) Follicle (2) Paracortex (3) Medullary sinus (4) Medullary cords.

Answer 12

(1) B cells (2) T cells (3) Macrophages (4) Plasma cells

Question 13

What are the 3 areas of the body that have an axillary primary lymph node drainage site?

Answer 13

Upper limb, lateral breast, skin above umbilicus

Question 14

What are the areas of the body that have the following primary lymph node drainage sites: (1) Celiac (2) Superior mesenteric (3) inferior mesenteric

Answer 14

(1) Liver, stomach, spleen, pancreas, upper duodenum (2) lower Duodenum, jejunum, ileum, colon to splenic flexure (3) Colon from splenic flexure to upper rectum

Question 15

What are the 2 areas of the body that have a superficial inguinal primary lymph node drainage site?

Answer 15

(1) Anal canal (below pectinate line) (2) skin below umbilicus (except popliteal territory)

Question 16

What are the areas of the body that have the following primary lymph node drainage sites: (1) Internal iliac (2) Para-aortic

Answer 16

(1) Lower rectum to anal canal (above pectinate line), bladder, vagina (middle third), prostate (2) Testes, ovaries, kidneys, uterus

Question 17

What are the 2 areas of the body that have a popliteal primary lymph node drainage site?

Answer 17

Dorsolateral foot, posterior calf

Question 18

What are the names of the 2 lymph ducts in the body? What does each drain?

Answer 18

(1) Right lymphatic duct - drains right side of body above diaphragm (2) Thoracic duct - drains everything else into junction of left subclavian and internal jugular vein

Question 19

Draw a visual of a sinusoid of spleen, labeling the following: (1) Arterial supply (2) Germinal center (B cells) (3) Central arteriole (4) Red pulp (RBCs) (5) Section of white pulp (6) PALS (T cells) (7) Venous drainage.

Answer 19

See p. 193 in First Aid for visual

Question 20

Define the sinusoids of the spleen. Include what they are, where they are, and what kind of basement membrane is associated within them.

Answer 20

Long, vascular channels in red pulp with fenestrated “barrel hoop” basement membrane

Question 21

Where are T cells found in the spleen?

Answer 21

T cells are found within the periarterial lymphatic sheath (PALS) within the white pulp of the spleen

Question 22

Where are B cells found in the spleen?

Answer 22

B cells are found in the follicles within white pulp of spleen

Question 23

What types of cells are found nearby the sinusoids of spleen? What function do these cells serve in spleen?

Answer 23

Macrophages found nearby; Macrophages in spleen remove encapsulated bacteria

Question 24

What are the consequences of splenic dysfunction? List them as a sequence of events.

Answer 24

Splenic dysfunction: decreased IgM –> decreased complement activation –> decreased C3b opsonization –> increased susceptibility to encapsulated organisms

Question 25

To what type of organisms do patients with splenic dysfunction have an increased susceptibility? Give specific examples of such organisms.

Answer 25

Increased susceptibility to encapsulated organisms: Streptococcus pneumoniae, Haemophilus influenzae type B, Neisseria meningitidis, E. coli, Salmonella, Klebsiella pneumoniae, Group B Streptococci; Think: “SHiNE SKiS”

Question 26

What 2 major findings can be seen on blood smear postsplenectomy? What other hematological abnormality occurs postsplenectomy?

Answer 26

(1) Howell-Jolly bodies (nuclear remnants) (2) Target cells; Thrombocytosis

Question 27

What function does the thymus serve?

Answer 27

Site of T-cell differentiation and maturation

Question 28

What is the embryological origin of the thymus? What is a key structural/physical feature of the thymus?

Answer 28

From epithelium of 3rd branchial pouches; Encapsulated

Question 29

What is the origin of lymphocytes in the thymus?

Answer 29

Lymphocytes of mesenchymal origin

Question 30

What is the difference between the thymus cortex versus medulla in terms of appearance?

Answer 30

CORTEX is dense with immature T cells; MEDULLA is pale with mature T cells and epithelial reticular cells containing Hasall’s corpuscles

Question 31

What types of cells are found in the thymus cortex versus medulla?

Answer 31

CORTEX is dense with immature T cells; MEDULLA is pale with mature T cells and epithelial reticular cells containing Hasall’s corpuscles

Question 32

Where in the thymus does positive versus negative selection occur?

Answer 32

Positive selection (MHC restriction) occurs in the cortex and Negative selection (nonreactive to self) occurs in the medulla.