Lymphoid Pathology I Flashcards
What is the link between the thymus and T-Cells?
The thymus is where T-Cells mature so that they do not attack self cells
What are the two different types of selection occuring in the thymus?
Positive and negative selection
What are the differences between positive and negative selection?
- 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
What are the three functions of lymph nodes?
- 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
How does blood flow through the spleen?
Through the central artery and then exits out of the marginal zone
What does the spleen effectively act as?
A sieve
What are MALT, BALT, GALT and tonsils essentially?
A lymphoid follicle that subtends a mucousal surface
What is the usual histopathology of atrophy?
- Decreased Follicle Size
- Increased Lymphocytolysis
- Fibrosis
What can cause atrophy?
- Lack of an antigenic stimulus
- Viruses, such as canine distemper
- Malnutrition
- Toxins
- Ionising radiation
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What is the gross pathology of hypertrophy?
- Organ will be bigger
- Can sometimes see follicles
- Its common in most lymphoid organs apart from the thymus
What does lymphoid hyperplasia look like?
- Increased numbers of lymphoid follicles with prominent germinal centres
- Follicles may extend into new areas
- Increased number of T Cells
What can cause Hyperplasia?
- Chronic antigenic stimulation
- Infectious agents
- Immune dysregulation
- Autoimmune diseases
- Hypersensitivities
- Neoplasia
How can you recognise the chronic phase of inflammation?
Organs may be enlarged
What does the histiocytosis of hypertrophy look like?
- Increased number of monocyte-macrophages
- Histocytosis in the sinus of lymph nodes
- hyperplasia in the red pulp of the spleen
What can acute phase and chronic inflammation look like grossly?
- Acute phase- oedema, haemorrhage, suppurative inflammtion
- Chronic- organ can either be enlarged or can be smaller, depending on the agent causing it
How may you recognise neoplasia grossly?
- Primary Neoplasia- Diffuse enlargement, +/ - loss of the normal architecture
- Metastatic disease- Discrete nodules, can also look like diffuse enlargement
What are some of the aetiologies of bloody/ haemorrhaged spleens?
- Euthanaesia
- Septicaemia
- Anthrax
- African Swine Fever
- Haemolysis
What is splenomegaly?
An enlarged spleen
What does a congested splenomegaly look like?
- Red Pulp Congestion
- Haemorrhage
What is the basic structure of the spleen?
Splenic follicles with germinal centres
(White pulp surrounded by red pulp)
What is haemoabdomen?
Term used to describe free blood within the abdominal cavity
What can occur if the splenic nodules rupture?
Haemoabdomen
What is the Gross Pathology of Splenic Nodules?
- Can be focal or multifocal and elevate the capsular surface
- can be soft or firm- red to pale tan to white
What are some of the differentials for splenic nodules?
- Haematomas
- Nodular hyperplasia
- Neoplasia
- Inflammation
What is another term for a non-congested splenomegaly?
‘meaty-spleen’
What is an important non-infectious cause for meaty spleen?
amyloidosis
What are the four important differentials for splenic nodules?
- Haematoma
- Neoplasia
- lymphoid nodular hyperplasia
- Inflammation
What causes lymphadomegaly?
Draining inflammation
Neoplastic metastasis
Where do neoplastic cells first typically appear?
They first appear in the subcapsular sinuses
What are the three functions of the lymph nodes?
- To filter lymph of particulate matter and microorganisms
- to facilitate the processing and surveilance of incoming antigens via interactions with B and T cells
- To produce B lymphocytes and plasma cells
How can you recognise neoplasia histopathologically?
- Sheets of monomorphic cells
- lymphocytes, histiocytes, supporting cells
- or a metastatic disease- any cells that aren’t typically in a lymphoid organ
What are some of the aetiologies of splenomegaly?
- Euthanaesia, Anaesthesia,
- Splenic volvulus
- Anthrax,
- African swine fever, Haemolysis (extravascular)
What are some of the aetiologies for a non-congested splenomegaly?
- Red-pulp histiocytosis
- granulomatous inflammation
- Histiocytic inflammation
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What causes lymphadenomegaly?
Draining inflammation
-first appears in the subcapsular sinus
Name some primary and secondary lymphoid organs
- Primary- Bone Marrow, Thymus, Bursa of fabricans
- Secondary- lymph nodes, spleen, MALT, GALT, tonsils etc.
