Lymphoid system (Goyal)

Question 1

What are the main components of the lymphoid system?

Answer 1

1. Lymphoid (lymphocytes + antigen presenting cells)
2. Diffuse lymphoid tissue (aggregation of lymphoid cells in CT)
3. Solitary lymph nodules (mucosa of digestive or resp. organs)
4. Aggregation of lymph nodules (Peyer’s patch)
5. Discrete lymphoid organs (LN, hemal nodes, tonsils, thymus, spleen)

Question 2

What are the cells of the immune system?

Answer 2

B and T cells
Plasma cells
T helper cells (CD4+)
T cytotoxic cells (CD8+)
T suppressor cells (CD8+)
Natural Killer cells (nonspecific cytotoxicity)

Question 3

Antigen presenting cells

Answer 3

Dendritic cell in LN
Langerhans in skin
Macrophages
B lymphocytes

Question 4

What do all antigen presenting cells possess?

Answer 4

MHC class II molecules on their surface and exogenous antigens to T helper cells

Question 5

IgA

Answer 5

Binds to epithelium covering or lining organs of the body

Question 6

IgD

Answer 6

Binds to plasma membrane of B cells

Question 7

IgE

Answer 7

Binds to plasma membrane of mast cells and basophils

Question 8

IgG

Answer 8

80% of total serum Ig

Question 9

IgM

Answer 9

First antibody produced in a primary immune response and in the neonate
Present in serum and on plasma membrane of B cells

Question 10

_________ are the only leukocytes that recirculate between blood and CT

Answer 10

Lymphocytes

Question 11

What is the role of Peyer’s patches in ruminants?

Answer 11

A source of B cell differentiation (in addition to the bone marrow)

Question 12

Tonsils

Answer 12

Lymph nodule aggregation in CT under epithelium
3: lingual, palatine, pharyngeal

Question 13

What are lingual and palatine tonsils covered by?

Answer 13

Stratified squamous epithelium

Question 14

What are pharyngeal tonsils covered by?

Answer 14

Pseudostratified epithelium

Question 15

T/F: Epithelial surface of palatine Tonsils of dogs and cats of may be smooth

Answer 15

TRUE

Question 16

Which epithelial surface of tonsils have deep invaginations?

Answer 16

Lingual tonsils in horses
Palatine tonsils in horses and small ruminants

Question 17

What do tonsils lack?

Answer 17

Afferent lymph vessels, so they can’t filter lymph but contain efferent lymph vessels

Question 18

What do epithelial invaginations of a the palatine tonsil of a horse lead to?

Answer 18

Formation of a tonsillar crypt, which is the site for accumulation of food and organisms, then leading to tonsilitis

Question 19

What are the structures of lymph nodes?

Answer 19

Stroma, outer cortex, inner cortex (paracortex) , circulating lymphocytes, medulla , sinusoids

Question 20

Outer cortex

Answer 20

Lymph nodules
Germinal center
B lymphocytes mainly
Activation in response to foreign antigens

Question 21

Stroma

Answer 21

Capsule (Dense CT, afferent lymph vessels enter)
Trabeculae
Reticular fibers

Question 22

Inner cortex (paracortex)

Answer 22

Contains mainly T lymphocytes
Site where circulating lymphocytes gain access to LN via post- capillary venules (high endothelial- simple cuboidal)

Question 23

Medulla

Answer 23

Medullary cords: composed of lymphocytes, plasma cells and macrophages

Question 24

Sinusoids

Answer 24

Sub-capsular, trabecular or cortical and medullary
Surround medullary cords

Question 25

What is the flow to lymph in LN?

Answer 25

Afferent lymph vessel --> Sub-capsular sinusoids --> Trabecular sinusoid --> Medullary sinusoids --> Efferent lymph vessel

Question 26

What is the function of LN?

Answer 26

Filtration of lymph Phagocytosis of foreign particles Mounting an immune response Retention of tumor cells

Question 27

Porcine LN

Answer 27

Centrally located Medullary cords absent Lymph vessels exit @ periphery Afferent vessels enter @ capsule and penetrate via the trabeculae to the nodules

Question 28

Hemal Nodes

Answer 28

Present in ruminants Lack lymph vessels and receive cells from blood

Question 29

Diapedesis

Answer 29

Junction between cuboidal cells are loose This enables lymphocytes to leave the blood and enter the LN

Question 30

Thymus

Answer 30

Epithelio-lymphoid organs made of lobes and lobules (divided into cortex and medulla)

Question 31

Thymus cortex

Answer 31

Aggregation of lymphocytes Blood-thymus barrier in cortex enables T cell differentiation in the absence of external antigens

Question 32

Thymus medulla

Answer 32

Compared to cortex, has fewer lymphocytes and more epithelial-reticular cells (with age degenerate and form Hassall's corpuscles)

Question 33

Thymus function

Answer 33

Priming of T cells tha migrate to rest of the body Contains efferent lymph vessels

Question 34

How is the thymus effected with age?

Answer 34

Atrophies with age, but small amount of tissue persists througout life

Question 35

Effects of thymectomy @ neonatal age

Answer 35

Reduced # of lymphocytes Atrophy of all lymphoid organs No delayed hypersensitivity or graft rejection Animals eventually become weak, lose weight and dies

Question 36

What are the different parts of the spleen?

Answer 36

Capsule, Trabeculae, Red pulp, White pulp

Question 37

Spleen trabeculae

Answer 37

Contains blood vessels. nerves, fibers and smooth muscle cells (especially developed in the horse)

Question 38

Red pulp

Answer 38

Contains sinusoids and cords Cords: between sinusoids and have RBCs. macrophages, lymphocytes, plasma cells and other leukocytes

Question 39

Sinusoids in the spleen

Answer 39

Wide capillaries lined by endothelial cells with spaces between cells Discontinuous BL

Question 40

White pulp

Answer 40

Periateriolar lymphaic sheath (T cells surrounding central arteriole) and lymphaic nodules (B cells)

Question 41

Lymph nodules of white pulp?

Answer 41

Germinal center: B cell proliferation Mantle zone: B cell aggregation Marginal zone: B and T cells, macrophages

Question 42

Marginal zone of the spleen

Answer 42

Between white and red pulp First site in the spleen where blood antigens get an access to immunocompetent cells

Question 43

What are the functions of the spleen?

Answer 43

Filter blood B and T cell proliferation Phagocytosis of old RBC Storage of blood and release Prenatal hematopoiesis

Question 44

What are the 3 types of spleen?

Answer 44

Defense, storage and intermediate

Question 45

Defense spleen

Answer 45

Lymphatic tissue Man, rabbits and hares

Question 46

Storage spleen

Answer 46

Red tissue Horses, dogs and cats

Question 47

Intermediate spleen

Answer 47

Ruminants and swine

Question 48

What gives capillaries to the white pulp?

Answer 48

Splenic, trabecular and central (arteriole) artery

Question 49

Penicillus

Answer 49

Brush-like Enters the red pulp as arteriole of the red pulp and continues as sheathed arterioles Surrounded my macrophages Pigs and cats

Question 50

Closed circulation

Answer 50

Sheathed capillaries that open into sinusoids of the red pulp

Question 51

Open cirucaltion

Answer 51

Sheathed capillaries that open into cords of the red pulp

Question 52

Bursa Fabricus in cloaca of birds

Answer 52

An aggregation of lymph nodules under the cloacal epithelium Site for B cell differentiation Simple columnar and pseudostraitifed columnar