Lecture 14: Blood and Lymph

Question 1

Where is hematopoiesis completed in embryos, fetuses and adults?

Answer 1

Embry: yolk sac
Fetus: Liver and spleen
Adult: bone marrow, extramedullary hematopoiesis can occur in the spleen if needed

Question 2

How does the gross features of bone marrow change over time in a normal animal?

Answer 2

The hematopoietic function transitions into adipose storage functions resulting in a colour change. When the animal is younger the bone marrow is red and it becomes more yellow as the animal ages

Question 3

What is hematopoiesis?

Answer 3

It is the production of blood cells from hematopoiesis

erythropoiesis
granulopoiesis (neutrophil/basophil/eosinophil)
thrombopoiesis (platelet)

Question 4

What is the pathway of differentiation of blood cells in the bone marrow?

Answer 4

1. common pluripotent hematopoietic stem cell - these cells can self renew
2. 1st commitment is either myeloid or lymphoid

myeloid cells further mature into granulocytes, erythrocytes, or platelets

lymphoid cells become either B or T cells

Question 5

Compare the lifespans of 3 major blood cells and how does it impact an animals clinical presentation of cytopenia?

Answer 5

Neutrophils have the shortest lifespan followed by platelets then erythrocytes

This means that in a cytopenia, a neutropenia is the first thing that will be evident

Question 6

What is a hallmark sign of infection and why does it occur?

Answer 6

left shift neutrophils

This is the release of immature neutrophils from the bone marrow. Normally only mature cells are released but in this case the surplus of cells is exhausted by inflammation

Question 7

How is the population of mature cells increased in a normal animal?

Answer 7

There is increased division of immature cells

Mature cells cannot divide

Question 8

How is hematopoiesis controlled?

Answer 8

There are systemic and local controls with lots of redundancy

This creates a fast and predictable response to balance production and turnover in a normal range

Question 9

List 4 types of bone marrow dysfunction?

Answer 9

• hypoplasia/aplasia
• myelophthisis
• inflammation
• neoplasia

Question 10

List 2 dysfunctions of the peripheral blood

Answer 10

cytopenia
cytosis or ‘philia’

The outcome depends on the type of cell that is injured
- pluripotent cell = pancytopenia
- differentiated cell = impact single cell line

Bone marrow and peripheral blood are linked

Question 11

How can anemia result in both erythroid hypoplasia and hyperplasia?

Answer 11

Erythroid hypoplasia can result from a non-regenerative anemia due to bone marrow injury

Erythroid hyperplasia can result from hemorrhage and regenerative anemia

Question 12

Compare bone marrow hypoplasia and aplasia

Answer 12

Hypoplasia results in fewer hematopoietic cells and aplasia results in no hematopoietic cells

This both results in a reduction in proliferative activity that can impact 1+ cell lines

Question 13

Define aplastic anemia

Answer 13

reduced hematopoietic activity in >1 cell line due to bone marrow hypoplasia or aplasia

This will cause a pancytopenia

Question 14

What type of anemia is caused by bone marrow hypoplasia or aplasia?

Answer 14

nonregenerative

Question 15

What can cause bone marrow hypoplasia or aplasia?

Answer 15

drugs or toxins like estrogen in dogs or chemotherapy

infectious - parvo

reduced stimulation - reduced erythropoietin in CKD

myelophthisis

idiopthic

Question 16

What is myelophthisis?

Answer 16

It is the replacement of hematopoietic tissue from inside the bone marrow

Question 17

What are the potential causes of mylelophthisis?

Answer 17

fibrin: myelofibrosis

neoplasia

inflammation: myelitis

Question 18

What is a characteristic bone marrow lesion of a calf with lymphoma?

Answer 18

Myelophthisis: Invasion with pale neoplastic tissue

Question 19

How can the nutritional status of an animal be discerned from the bone marrow?

Answer 19

Look for serous atrophy of fat: gelatinous marrow (fat cell atrophy) and extracellular mucin deposits

If it is present it indicates a significant negative energy balance because the bone marrow is one of the last places energy is removed from (SC > omentum/mesentery > deep organ fat in kidney/heart > bone marrow)

This is associated with malnutrition/cachexia/GI parasitism

Question 20

What is bone marrow hyperplasia?

Answer 20

increased numbers of hematopoietic cells

Question 21

What causes bone marrow hyperplasia?

Answer 21

stimuli:
- hypoxia or anemia causes increased erythropoietin and erythroid hyperplasia

• inflammation causes increased cytokines and granulocytic hyperplasia
• thrombocytopenia causes increased thrombopoietin and megakaryocytic hyperplasia

Question 22

What are the gross indications of bone marrow hyperplasia?

Answer 22

Diffusely red bone marrow but histology and/or a CBC is needed to determine which cell line(s) are affected

Question 23

What are the categories of anemia?

Answer 23

Non regenerative

Regenerative due to
- hemorrhage
- hemolysis (intra or extra vascular)

Question 24

What are the common lesions associated with anemia? Why do they occur?

Answer 24

depends on type of anemia

pale MM

icterus if there is hemolysis (both extra or intra vascular)

splenomegaly due to extravascular hemolysis (lots of macrophages cleaning RBC and intramedullary hematopoiesis)

hemoglobiinuria/hemaglobinemia/hemoglobinuric nephrosis due to intravascular hemolysis

Question 25

What is leukemia?

Answer 25

It is hematopoietic neoplasia from the bone marrow in the blood

Question 26

List 3 types of myeloproliferative neoplasias?

Answer 26

myeloid leukemia
histiocytic neoplasia
mast cell neoplasia

Question 27

List 3 types of lymphoproliferative neoplasias?

Answer 27

lymphoma (most common)
plasma cell neoplasia
lymphoid leukemia

Question 28

What factors are used to classify lymphoma?

Answer 28

Anatomic location (multicentric, alimentary, thymic …)

immunophenotype (B or T)

cell morphology (small vs large)

histologic pattern (follicular or diffuse)

behaviour (low vs high grade)

Question 29

What are the gross features of lymphoma?

Answer 29

lymphadenomegaly
multiple tan solf nodular masses
organomegaly
thick tubular organs

Question 30

Compare 2 types of bovine lymphoma

Answer 30

enzootic bovine leukemia
- BLV associated
- older (7-8y)
- dairy > beef
- multicentric B cell

sporadic
- not BLV associated
- young
- T cell either multicentric (calves, thymic or cutaneous

Question 31

How is virally transmitted bovine lymphoma transmitted? How does it present clinically?

Answer 31

bovine leukemia virus can cause enzootic bovine lymphoma in <5% of cases but in 30% of cases it can cause a persistent lymphocytosis

Lymphoma can affect lymph nodes, retrobulbar spaces, abomasum, heart, uterus, spleen, liver, uterus, vertebral canal

Question 32

In what type of dog would you expect lymphoma to develop?

Answer 32

Not virus associated

common in mid-old dogs

It can be associated with hypercalcemia of malignancy due to parathyroid hormone related peptide release from tumor

Question 33

Describe the location(s) and behaviour of canine lymphoma

Answer 33

Mainly it is multicentric
Can also occur in GI > cutaneous > thymic

It is a mid-high grade tumor

Question 34

Describe the type of cat you would expect to see lymphoma in? How is it related to the location of the tumor?

Answer 34

It is common

Found in GI in FeLV negative cats = most common

multicentric and thymic locations are associated with FeLV

GI > multicentric > thymic > other

Question 35

What is the most common horse malignancy? and where does it develop?

Answer 35

Most common is equine lymphoma - it is a T cell rich large B cell lymphoma

common in adult horses

multicentric > cutaneous > GI