Lymphoid Pathology I

Question 1

What is the link between the thymus and T-Cells?

Answer 1

The thymus is where T-Cells mature so that they do not attack self cells

Question 2

What are the two different types of selection occuring in the thymus?

Answer 2

Positive and negative selection

Question 3

What are the differences between positive and negative selection?

Answer 3

• Positive selection occurs in the capsule and occurs when T Cells recognise self-MHC molecules and they then mature
• Negative Selection occurs in the medulla and it occurs when a T-Cell recognises a self-antigen then undergoes apoptosis

Question 4

What are the three functions of lymph nodes?

Answer 4

• to filter lymph of
  particulate matter and
  microorganisms
• to facilitate the
  surveillance and
  processing of incoming
  antigens via interactions
  with B and T lymphocytes
  to produce B
• lymphocytes and plasma
  cells
  maturation of B cells

Question 5

How does blood flow through the spleen?

Answer 5

Through the central artery and then exits out of the marginal zone

Question 6

What does the spleen effectively act as?

Answer 6

A sieve

Question 7

What are MALT, BALT, GALT and tonsils essentially?

Answer 7

A lymphoid follicle that subtends a mucousal surface

Question 8

What is the usual histopathology of atrophy?

Answer 8

• Decreased Follicle Size
• Increased Lymphocytolysis
• Fibrosis

Question 9

What can cause atrophy?

Answer 9

• Lack of an antigenic stimulus
• Viruses, such as canine distemper
• Malnutrition
• Toxins
• Ionising radiation
  *

Question 10

What is the gross pathology of hypertrophy?

Answer 10

• Organ will be bigger
• Can sometimes see follicles
• Its common in most lymphoid organs apart from the thymus

Question 11

What does lymphoid hyperplasia look like?

Answer 11

• Increased numbers of lymphoid follicles with prominent germinal centres
• Follicles may extend into new areas
• Increased number of T Cells

Question 12

What can cause Hyperplasia?

Answer 12

• Chronic antigenic stimulation
• Infectious agents
• Immune dysregulation
• Autoimmune diseases
• Hypersensitivities
• Neoplasia

Question 13

How can you recognise the chronic phase of inflammation?

Answer 13

Organs may be enlarged

Question 14

What does the histiocytosis of hypertrophy look like?

Answer 14

• Increased number of monocyte-macrophages
• Histocytosis in the sinus of lymph nodes
• hyperplasia in the red pulp of the spleen

Question 15

What can acute phase and chronic inflammation look like grossly?

Answer 15

• Acute phase- oedema, haemorrhage, suppurative inflammtion
• Chronic- organ can either be enlarged or can be smaller, depending on the agent causing it

Question 16

How may you recognise neoplasia grossly?

Answer 16

• Primary Neoplasia- Diffuse enlargement, +/ - loss of the normal architecture
• Metastatic disease- Discrete nodules, can also look like diffuse enlargement

Question 17

What are some of the aetiologies of bloody/ haemorrhaged spleens?

Answer 17

• Euthanaesia
• Septicaemia
• Anthrax
• African Swine Fever
• Haemolysis

Question 18

What is splenomegaly?

Answer 18

An enlarged spleen

Question 19

What does a congested splenomegaly look like?

Answer 19

• Red Pulp Congestion
• Haemorrhage

Question 20

What is the basic structure of the spleen?

Answer 20

Splenic follicles with germinal centres
(White pulp surrounded by red pulp)

Question 21

What is haemoabdomen?

Answer 21

Term used to describe free blood within the abdominal cavity

Question 22

What can occur if the splenic nodules rupture?

Answer 22

Haemoabdomen

Question 23

What is the Gross Pathology of Splenic Nodules?

Answer 23

• Can be focal or multifocal and elevate the capsular surface
• can be soft or firm- red to pale tan to white

Question 24

What are some of the differentials for splenic nodules?

Answer 24

• Haematomas
• Nodular hyperplasia
• Neoplasia
• Inflammation

Question 25

What is another term for a non-congested splenomegaly?

Answer 25

‘meaty-spleen’

Question 26

What is an important non-infectious cause for meaty spleen?

Answer 26

amyloidosis

Question 27

What are the four important differentials for splenic nodules?

Answer 27

• Haematoma
• Neoplasia
• lymphoid nodular hyperplasia
• Inflammation

Question 28

What causes lymphadomegaly?

Answer 28

Draining inflammation
Neoplastic metastasis

Question 29

Where do neoplastic cells first typically appear?

Answer 29

They first appear in the subcapsular sinuses

Question 30

What are the three functions of the lymph nodes?

Answer 30

1. To filter lymph of particulate matter and microorganisms
2. to facilitate the processing and surveilance of incoming antigens via interactions with B and T cells
3. To produce B lymphocytes and plasma cells

Question 31

How can you recognise neoplasia histopathologically?

Answer 31

• Sheets of monomorphic cells
• lymphocytes, histiocytes, supporting cells
• or a metastatic disease- any cells that aren’t typically in a lymphoid organ

Question 32

What are some of the aetiologies of splenomegaly?

Answer 32

• Euthanaesia, Anaesthesia,
• Splenic volvulus
• Anthrax,
• African swine fever, Haemolysis (extravascular)

Question 33

What are some of the aetiologies for a non-congested splenomegaly?

Answer 33

• Red-pulp histiocytosis
• granulomatous inflammation
• Histiocytic inflammation
  *

Question 34

What causes lymphadenomegaly?

Answer 34

Draining inflammation
-first appears in the subcapsular sinus

Question 35

Name some primary and secondary lymphoid organs

Answer 35

• Primary- Bone Marrow, Thymus, Bursa of fabricans
• Secondary- lymph nodes, spleen, MALT, GALT, tonsils etc.