Lecture 14: Blood and Lymph Flashcards
Where is hematopoiesis completed in embryos, fetuses and adults?
Embry: yolk sac
Fetus: Liver and spleen
Adult: bone marrow, extramedullary hematopoiesis can occur in the spleen if needed
How does the gross features of bone marrow change over time in a normal animal?
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
What is hematopoiesis?
It is the production of blood cells from hematopoiesis
erythropoiesis
granulopoiesis (neutrophil/basophil/eosinophil)
thrombopoiesis (platelet)
What is the pathway of differentiation of blood cells in the bone marrow?
- common pluripotent hematopoietic stem cell - these cells can self renew
- 1st commitment is either myeloid or lymphoid
myeloid cells further mature into granulocytes, erythrocytes, or platelets
lymphoid cells become either B or T cells
Compare the lifespans of 3 major blood cells and how does it impact an animals clinical presentation of cytopenia?
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
What is a hallmark sign of infection and why does it occur?
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
How is the population of mature cells increased in a normal animal?
There is increased division of immature cells
Mature cells cannot divide
How is hematopoiesis controlled?
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
List 4 types of bone marrow dysfunction?
- hypoplasia/aplasia
- myelophthisis
- inflammation
- neoplasia
List 2 dysfunctions of the peripheral blood
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
How can anemia result in both erythroid hypoplasia and hyperplasia?
Erythroid hypoplasia can result from a non-regenerative anemia due to bone marrow injury
Erythroid hyperplasia can result from hemorrhage and regenerative anemia
Compare bone marrow hypoplasia and aplasia
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
Define aplastic anemia
reduced hematopoietic activity in >1 cell line due to bone marrow hypoplasia or aplasia
This will cause a pancytopenia
What type of anemia is caused by bone marrow hypoplasia or aplasia?
nonregenerative
What can cause bone marrow hypoplasia or aplasia?
drugs or toxins like estrogen in dogs or chemotherapy
infectious - parvo
reduced stimulation - reduced erythropoietin in CKD
myelophthisis
idiopthic
What is myelophthisis?
It is the replacement of hematopoietic tissue from inside the bone marrow
What are the potential causes of mylelophthisis?
fibrin: myelofibrosis
neoplasia
inflammation: myelitis
What is a characteristic bone marrow lesion of a calf with lymphoma?
Myelophthisis: Invasion with pale neoplastic tissue
How can the nutritional status of an animal be discerned from the bone marrow?
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
What is bone marrow hyperplasia?
increased numbers of hematopoietic cells
What causes bone marrow hyperplasia?
stimuli:
- hypoxia or anemia causes increased erythropoietin and erythroid hyperplasia
- inflammation causes increased cytokines and granulocytic hyperplasia
- thrombocytopenia causes increased thrombopoietin and megakaryocytic hyperplasia
What are the gross indications of bone marrow hyperplasia?
Diffusely red bone marrow but histology and/or a CBC is needed to determine which cell line(s) are affected
What are the categories of anemia?
Non regenerative
Regenerative due to
- hemorrhage
- hemolysis (intra or extra vascular)
What are the common lesions associated with anemia? Why do they occur?
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
What is leukemia?
It is hematopoietic neoplasia from the bone marrow in the blood
List 3 types of myeloproliferative neoplasias?
myeloid leukemia
histiocytic neoplasia
mast cell neoplasia
List 3 types of lymphoproliferative neoplasias?
lymphoma (most common)
plasma cell neoplasia
lymphoid leukemia
What factors are used to classify lymphoma?
Anatomic location (multicentric, alimentary, thymic …)
immunophenotype (B or T)
cell morphology (small vs large)
histologic pattern (follicular or diffuse)
behaviour (low vs high grade)
What are the gross features of lymphoma?
lymphadenomegaly
multiple tan solf nodular masses
organomegaly
thick tubular organs
Compare 2 types of bovine lymphoma
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
How is virally transmitted bovine presenting clinically?
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
In what type of dog would you expect lymphoma to develop?
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
Describe the location(s) and behaviour of canine lymphoma
Mainly it is multicentric
Can also occur in GI > cutaneous > thymic
It is a mid-high grade tumor
Describe the type of cat you would expect to see lymphoma in? How is it related to the location of the tumor?
It is common
Found in GI in FeLV negative cats = most common
multicentric and thymic locations are associated with FeLV
GI > multicentric > thymic > other
What is the most common horse malignancy? and where does it develop?
Most common is equine lymphoma - it is a T cell rich large B cell lymphoma
common in adult horses
multicentric > cutaneous > GI
