topic 5: differencial cell count: wbc Flashcards
What is a differential count?
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)
size and colour of neutrophils
Large (2x RBC)
“Polymorphonuclear leukocytes”
elongated, segmented nucleus with 3-5 lobes
Light grey-blue cytoplasm (granules are usually indiscernible)
function of neutrophils
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
Causes of Neutrophilia:
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)
what are band neutrophils
Immature; left bone marrow pre-maturely
Elongated, non-lobulated nucleus
(baby neutrophils)
what is left shift and what are the two different catergories of left shift
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
what is right shift
Increased number of hypersegmented neutrophils in circulation (aging change)
grandpa neutrophils
what are toxic neutrophils
Due to severe inflammatory disease, accelerated neutrophil production & shortened maturation time
(never mature properly)
what are the characteristics of toxic neutrophils
Doehle bodies (RER remnants
Pink-purple cytoplasmic granulation
Basophilic cytoplasm
Cytoplasmic vacuolation
Causes of Neutropaenia:
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.
size and colour of lymphocytes
Large (same size as neutrophils)
Round, densely stained nucleus
Scant blue cytoplasm
Lymphopoiesis = production of lymphocytes
(occurs un tyhymus, spleen, lymph nodes)
function and types of lymphocytes
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
how much lymphocytes is there in the blood
Only 5% total body lymphocyte pool circulates in blood
(rest remain in lymph node or speen)
Causes of Lymphocytosis:
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
Causes of Lymphopaenia:
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
size and colour of eosinophils
Slightly larger than neutrophil
Segmented nucleus (2/3 lobes)
Coarse eosinophilic cytoplasmic granules (rod- shaped and orangey-pink in the cat
function of eosinophil
Combating parasitic infections – they bind to opsonized parasites and degranulation kills parasite.
Promotes inflammation and tissue damage in allergic disease.
Causes of Eosinophilia:
Parasite burden (eg heartworm)
Hypersensitivity disorders (eg flea-bite dermatitis and feline asthma)
Causes of Eosinopaenia:
Stress/Steroids
steroids inhibit E release from bone marrow and promote sequestration of E into tissues.
Acute inflammation
size and colour of basophils
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.
function of basophils
Contain inflammatory mediators that expel parasites and recruit eosinophils to kill parasites.
Contains inflammatory mediators that are involved in Type 1 hypersensitivity reactions.
Causes of Basophilia:
Parasitism (eg dirofilaria)
Allergic disease (eg dermatitis)
Drug reactions (eg heparin, Penicillin)
colour and size of monocytes
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.
whats special about monocytes
MONOCYTES transform into MACROPHAGES when they leave the circulation.
function of monocyte: macrophage
Phagocytosis of foreign bodies and dead cells.
causes of monocytosis
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
Inflammatory Leukogram-inflammation or infection
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
Stress Leukogram
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)
Physiologic Leukogram
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
What happens when a recipient receives blood from an incompatible donor?
Incompatible – the recipient has antibodies to the donors blood antigens.
Incompatible blood transfusion result in Acute Haemolytic Reactions
Types of Antibodies
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)
what are the different canine blood types
8 major dog blood types.
Labeled “DEA” for Dog Erythrocyte Antigen.
Most potent antigens= DEA 1.1 and 1.2.
Two types of transfusion reactions:
Delayed transfusion reaction
Acute transfusion reaction
Delayed Transfusion reaction in dogs
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.
Acute Transfusion Reactions in dogs
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.
what are the different feline blood type
The AB blood system: Type A, Type B or Type AB.
How does haemolysis occur
Occurs via type 2 hypersensativity reaction
Cells expose than antigen, antibodies against them are produced
Antigen- antibody complex formation initiates the complement pathway, inflammmatory mediators attach to cells and cause cell lysis
What is neonatal isoerythrolysis in cats
Kitten has different blood type to mother so when kitten drink the colostrum, cause hemolytic anemia in kitten
When do we need to do blood transfusion
Anemia
Low platelets
What tests are done to do or before blood transfusion
Blood typing, identifying the RBC surface antigen
Corssmatching, mixing of plasma and cells from donor and recipient to see of there are compatible
What are common dogs for donors
Greyhounds or labs
How to do in house cross matching
Get blood sample from receipient and donor
Separate the serum (contains antibodies) from the blood cells (contains antigens attached to RBC)
Major cross match: donor blood cell with repellent serum
Minor corssmatch: mix receipient blood cells with oboes serum
Presence of hemolyais and agglutination indicates incompatibility ( under microscope) d
What are the different steps of haemostasis
Primary haemostasis – formation of a platelet plug
•Secondary haemostasis – formation of fibrin clot
•Tertiary haemostasis – breakdown of the fibrin clot
What happens during primary hemostasis
Endothelial injury
▫Von Willebrand factor (vWF) exposed
•Platelet adhesion
▫Mediated by vWF
•Platelet activation
▫Causes further activation and recruitment of platelets.
•Platelets aggregation
▫form a primary platelet plug
What happens during secondary haemostasis
Coagulation cascade is initiated by the intrinsic and extrinsic pathways.
1.In the extrinsic pathway, tissue factor binds and activates factor VII.
In the intrinsic pathway, factors XII, XI, IX and VIII are activated.
•This activates factor X in the common pathway that converts prothrombin (II) to thrombin.
•This Thrombin burst converts fibrinogen to fibrin (I).
•The fibrin polymerizes (cross-links) to stabilize the platelet plug (thrombus)
What happens during tertiary hemostasis
Tissue plasminogen activator (TPA), released by endothelial cells converts plasminogen to plasmin.
•Fibrinolysis
▫plasmin lyses fibrinogen and fibrin within the clot
▫Byproducts of this lysis include ‘Fibrinogen Degradation Products’ (FDPs) and D-dimers
What is the disorder of primary hemostasis
Thrombocytopenia
Clinical signs: blood in urine, blood sneezed and petechiation (small blood shots on gums)
How to do platelet count
Platelet count (part of cbc or manual count on blood smear
Use citrate tube to minimise clumping
What are the causes of thrombocytopenia
decreased bone marrow production
Increased destruction
Increased consumption
Blood loss
Sequestration (hiding)
Inherited in grey phounds and cavalier Charles spaniels
Buccaneers mucosal bleeding time
Animal is sedated, upper lip is died back with gauze, shallow cut is made on inside of upper lip with lancet
-see the tame it takes for bleeding toes to stop
Tests for primary hemostasis disorders
- platelet count
-buccal mucosal bleeding time
-von williebrands factor
Tests for secondary hemostasis disorders
-activated clotting time (ACT)
Test for dificienxy in the intrinsic and common pathway or severe thrombocytopenia
—activated partial thromboplastin time (aPPT)
Test intrinsic and common pathwaymore sensitive to act as it does not require platelet to support the reaction
- prothrombin time (PT)
Test for deficiencies in the extrinsic and common pathway
-thrombin clot time (TCT)
Test for fibrinogen levels or presence of thrombin factor (heparin)
- antithrombin (AT)
Antithrombin is an inhibitor of thrombin and factor X (lower the better)
Which tests are done tut and which tube is used (secondary heamostsis disorder)
Activated partial thromboplastin time
Prothrombin time
Use citrate tube for these two tests
Tests for tertiary haemostasis disorders
- fibrinogen degradation products
- d dimers
Tests for tertiary haemostasis disorders
- fibrinogen degradation products
- d dimers
