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)