topic 5: differencial cell count: wbc

Question 1

What is a differential count?

Answer 1

A manual evaluation of a peripheral blood smear to obtain the relative percentage of each type of white blood cell.
It is performed using:
A stained blood smear
Microscope
Cell counter
(see under the microscope, u see the type of wbc, press counter on machine)

Question 2

size and colour of neutrophils

Answer 2

Large (2x RBC)
“Polymorphonuclear leukocytes”
elongated, segmented nucleus with 3-5 lobes
Light grey-blue cytoplasm (granules are usually indiscernible)

Question 3

function of neutrophils

Answer 3

Phagocytosis and Microbicidal action (first line defence)
Activated by inflammatory mediators
Adhere and emigrate through vessel wall into tissue
Chemotaxis (moves towards chemical attractant)
Phagocytosis and degranulation kills bacteria

Question 4

Causes of Neutrophilia:

Answer 4

Physiologic (Distress / Fear / Exercise) ( increase in epinephrine->increase in blood floe-> shif of cell from marginating pool to circulational pool)
Stress / Steroid Response (corticosteroids cause release of neutrophils from bone marrow, marginating pool-> circulation pool)
Acute Inflammation (Infectious / non-infectious) (cause stored and maturing pools of neutrophils to be released from bone marrow) (left shift, babies come out)

Question 5

what are band neutrophils

Answer 5

Immature; left bone marrow pre-maturely
Elongated, non-lobulated nucleus
(baby neutrophils)

Question 6

what is left shift and what are the two different catergories of left shift

Answer 6

Left shift = Presence of immature neutrophils in the circulation (left-> going back in the cycle)
Categorisation of Left shifts:
Regenerative – appearance of band neutrophils in circulation.
Degenerative – band neutrophils clearly outnumber the mature neutrophils in circulation

Question 7

what is right shift

Answer 7

Increased number of hypersegmented neutrophils in circulation (aging change)
grandpa neutrophils

Question 8

what are toxic neutrophils

Answer 8

Due to severe inflammatory disease, accelerated neutrophil production & shortened maturation time
(never mature properly)

Question 9

what are the characteristics of toxic neutrophils

Answer 9

Doehle bodies (RER remnants
Pink-purple cytoplasmic granulation
Basophilic cytoplasm
Cytoplasmic vacuolation

Question 10

Causes of Neutropaenia:

Answer 10

Severe Infection
Bacterial/Viral infections
Overwhelming demand and increased migration from circulation to tissues.
Reduced or ineffective production
Bone Marrow disease / drug toxicity
Endotoxic / Anaphylactic shock
Transient shift from circulating to marginating pool.

Question 11

size and colour of lymphocytes

Answer 11

Large (same size as neutrophils)
Round, densely stained nucleus
Scant blue cytoplasm
Lymphopoiesis = production of lymphocytes
(occurs un tyhymus, spleen, lymph nodes)

Question 12

function and types of lymphocytes

Answer 12

3 main types:
T cells (cell-mediated immunity)
B cells (humoral immunity)
Natural Killer cells

Respond to specific viral, bacterial and cancer antigens to make lymphocytes specialised WBCs

Question 13

how much lymphocytes is there in the blood

Answer 13

Only 5% total body lymphocyte pool circulates in blood
(rest remain in lymph node or speen)

Question 14

Causes of Lymphocytosis:

Answer 14

Physiologic (Fear, Excitement, Exercise) (epinephrine causes release of lymphocytes from spleen into circulation)
Chronic Inflammation (Infectious / Non-infectious) (lymph nodes response to antigen stimulation)
Lymphoproliferative disorders (Eg FeLV) (virus replicates in lymphocytes in lymph nodes, bone marrow, tissues-> causes neoplastic transformation of lymph nodes-> lumphoma)
Hypoadrenocorticism (Addison’s disease) (lack od steroid production by adrenal glad, steroild normally inhibits production or alter distribution of lymphocytes in body, no steroid-> lymphocyte out of control)
Recent vaccination

Question 15

Causes of Lymphopaenia:

Answer 15

Acute / Severe inflammation
Inflammatory mediators cause emigration of lymphocytes to infected (esp viral infections) /inflamed tissue and homing of lymphocytes to lymph nodes.
Steroid / Stress
Steroids cause immediate shift of lymphocytes out of circulation
In the long run, steroids cause lymphotoxic effects on lymphoid tissue, so they tone down (lymphoid hypoplasia)
Hyperadrenocorticism (Cushing’s disease)
Opposite of hypoadrenocorticism

Question 16

size and colour of eosinophils

Answer 16

Slightly larger than neutrophil
Segmented nucleus (2/3 lobes)
Coarse eosinophilic cytoplasmic granules (rod- shaped and orangey-pink in the cat

Question 17

function of eosinophil

Answer 17

Combating parasitic infections – they bind to opsonized parasites and degranulation kills parasite.
Promotes inflammation and tissue damage in allergic disease.

Question 18

Causes of Eosinophilia:

Answer 18

Parasite burden (eg heartworm)
Hypersensitivity disorders (eg flea-bite dermatitis and feline asthma)

Question 19

Causes of Eosinopaenia:

Answer 19

Stress/Steroids
steroids inhibit E release from bone marrow and promote sequestration of E into tissues.
Acute inflammation

Question 20

size and colour of basophils

Answer 20

Large granules that fill cytoplasm.
Contain histamine, heparin and mucopolysaccharides.
Similar morphologically and functionally to mast cells, but mast cells don’t circulate and settle in tissue.

Question 21

function of basophils

Answer 21

Contain inflammatory mediators that expel parasites and recruit eosinophils to kill parasites.
Contains inflammatory mediators that are involved in Type 1 hypersensitivity reactions.

Question 22

Causes of Basophilia:

Answer 22

Parasitism (eg dirofilaria)
Allergic disease (eg dermatitis)
Drug reactions (eg heparin, Penicillin)

Question 23

colour and size of monocytes

Answer 23

The largest leukocytes in circulation
Blue-grey, granular cytoplasm
Cytoplasmic granules are lysosomes that contain proteolytic enzymes.
Oval, bi-lobed or tri-lobed nucleus
Pseudopodia (short hair-like processes of plasma membrane) may project from cell margins.

Question 24

whats special about monocytes

Answer 24

MONOCYTES transform into MACROPHAGES when they leave the circulation.

Question 25

function of monocyte: macrophage

Answer 25

Phagocytosis of foreign bodies and dead cells.

Question 26

causes of monocytosis

Answer 26

Acute inflammation/infection
Even though they are less efficient phagocytes than neutrophils in bacterial infection, monocytosis is seen in endocarditis and other bacteremias

Chronic inflammation
Associated with mycotic and other granulomatous infections

Tissue necrosis
demand for macrophages

Severe stress
Endogenous cortisol release causes shift from marginating to circulating pool

Question 27

Inflammatory Leukogram-inflammation or infection

Answer 27

Neutrophilia – huge emigration to inflamed tissues, N released from bone marrow (left shift)
Neutropenia when >10% bands and high demand persists (eg overwhelming bacterial sepsis)
Lymphopaenia – with acute inflammation as L migrate to infected tissue.
or
Lymphocytosis – with chronic inflammation as lymphoid tissue produce specialised L.
Eosinopaenia – (can also be normal)
Monocytosis – in acute and chronic inflammation

Question 28

Stress Leukogram

Answer 28

Mature Neutrophilia – steroids cause decreased adhesion of marginating pool, and early release from bone marrow
Lymphopaenia – steroids cause shift out of circulation or lysis of lymphocytes
Eosinopaenia – steroids inhibit eosinophil production
Monocytosis – (dogs and horses)

Question 29

Physiologic Leukogram

Answer 29

Mature Neutrophilia – epinephrine cause decreased adhesion of marginating pool, and early release from bone marrow
Lymphocytosis – epinephrine cause shifting of lymphocytes from peripheral lymphoid tissue to circulation.
Eosinophils – unchanged
Monocytes – unchanged

Question 30

What happens when a recipient receives blood from an incompatible donor?

Answer 30

Incompatible – the recipient has antibodies to the donors blood antigens.

Incompatible blood transfusion result in Acute Haemolytic Reactions

Question 31

Types of Antibodies

Answer 31

Naturally occurring antibodies
Acquired antibodies
Produced after exposure to incompatible blood type
Forms of Exposure:
Previous blood transfusion (most common)
Vaccinations that contain foreign RBC antigens (less common)
Colostrum => Neonatal Isoerythrolysis (esp in Cats)

Question 32

what are the different canine blood types

Answer 32

8 major dog blood types.
Labeled “DEA” for Dog Erythrocyte Antigen.
Most potent antigens= DEA 1.1 and 1.2.

Question 33

Two types of transfusion reactions:

Answer 33

Delayed transfusion reaction
Acute transfusion reaction

Question 34

Delayed Transfusion reaction in dogs

Answer 34

Dogs don’t have naturally occurring antibodies to 1.1 or 1.2
So, the first time a 1.1 (or 1.2) negative dog is exposed to a 1.1 (or 1.2) positive blood, a Delayed Transfusion Reaction may occur.

It takes 7-10 days to get an antibody response to a new antigen.
Delayed TRs are usually mild or not detected.
This is why a dog receiving a blood transfusion for the first time generally doesn’t get cross matched.

Question 35

Acute Transfusion Reactions in dogs

Answer 35

Risk of acute haemolytic reactions in subsequent reactions.
Because dog now has antibodies to the 1.1 (or 1.2) positive blood.
Happens within minutes to 12 hours.

Clinical signs: tachycardia, dyspnea, collapse, hypotension, salivation, convulsions, weakness, vomiting, pyrexia.
Blood profile: Haemaglobinemia (due to hemolysis) and hyperbilirubinemia (macrophages in the liver and spleen destroy the donor RBCs).
Treatment (fluid therapy, steroids) may be unfruitful.
Prevention (ie cross-matching) is the only cure.

Question 36

what are the different feline blood type

Answer 36

The AB blood system: Type A, Type B or Type AB.