2.1 Red Blood Cells

Question 1

What are cytokines? Which ones are important for RBCs?

Answer 1

-Cytokines are small proteins that are crucial in controlling the growth and activity of other immune system cells and blood cells.
o Erythropoietin (Epo)
o Interleukins
o Inhibitory cytokines

Question 2

What is the stimulus and source of erythropoietin?

Answer 2

stimulus: hypoxia
source: kidney

Question 3

how long does erythropoiesis/ maturation take?

Answer 3

(5-) 7 days

Question 4

what are the cellular compartments of bone marrow relevant hemopoiesis? how do cells progress between these and where do they go from here?

Answer 4

stem cell compartment >
progenitor cell compartment >
precursor cell compartment >
peripheral blood >
peripheral tissues

Question 5

what is the progression of cell types in erythropoiesis? At what stage do cells stop dividing and only mature?

Answer 5

rubriblast > prorubricyte > rubricyte > metarubricyte > reticulocyte > erythrocyte

division stops around the rubricyte stage
there are other cell names that could be added to this list

Question 6

what is the rbc lifespan of cows, horses, dogs, and cats?

Answer 6

cow: 160d
horse: 145d
dog: 110d
cat: 70d

Question 7

Where are red blood cells phagocyosed mainly, and by what?

Answer 7

macrophages remove RBCs in the spleen

Question 8

what species is it more common to see anisocytosis?

Answer 8

bovine

Question 9

what species has pale staining platelets?

Answer 9

horses

Question 10

In what domestic species is it normal for RBCs to have central pallor?

Answer 10

dogs

Question 11

How do we prepare blood for a CBC and what is measured?

Answer 11

-Store blood in lavender top tube with anti-coagulant (EDTA)
RBC indices:
-MCV: average size of RBCs; microcytic, normocytic, macrocytic
-MCH: hemoglobin per RBC; uncommonly used
-MCHC: hemoglobin/ unit volume; hypochromic (increased central pallor - iron limitation), normochromic, hyperchromic
-rubricytes: immature RBC

Thrombocyte indices:
-MPV: average size of platelets; shift platelets are large and immature

Leukocyte differentials
Anisocytosis

Question 12

What can we use to detect total plasma protein?

Answer 12

hematocrit tube > refractometer

Question 13

what do different colours of hematocrit tubes signify?

Answer 13

normal - clear
lipidemia - white
hemoglobinemia - red. free hemoglobin present (more dominant than bilirubin). likely due to IV hemolysis
bilirubinemia - yellow. product of RBC breakdown, could be due to EV hemolytic disease or liver disease. Horses naturally have more bilirubin in their plasma.

Question 14

what part of a blood smear should we look at to see parasites?

Answer 14

feathered edge

Question 15

what might give us an artificially low platelet count from a machine? What species is this important for?

Answer 15

platelet clumps at the feathered edge. common in cats

Question 16

what is auto-agglutination? What should we consider when we see it?

Answer 16

-Antigen-antibody complexes on the RBC surface cross-linking/binding to each other
-Presents in a test tube as stippling of red cells, like bunches of grapes on the smear
-Consider: immune mediated pathogenesis

Question 17

what is rouleaux? When, where do we see it and what does it mean?

Answer 17

-line of connected
-Usually an artifact – especially in horses and cats
-Uncommon in dogs and ruminants
>When seen in dogs it may indicate that there is an increase in proteins – inflammatory globulins, APPs. Look at biochem panel to assess.

Question 18

what is the saline dilution test and what is it used for?

Answer 18

-Take a drop of blood and 4 drops of saline, then look at it under a microscope
Rouleaux → dispersal of RBCs
Agglutination → persistent RBC clumps

Question 19

what is polychromasia and when do we see it?

Answer 19

-Due to increased presence of darker staining immature RBCs – polychromatophils
-Bigger, bluer cells – Wright’s stain
-Released by bone marrow in response to decreased oxygen carrying capacity
-Limited in healthy animals
-Consider: regenerative bone marrow response
-not really seen in horse regenerative response < cow < dogs < cats

Question 20

what are reticulocytes and when do we see them?

Answer 20

-Bigger cells with residual RNA clumping in a reticular pattern
-Same as polychromatophils but stained with New Methylene Blue & Wright’s
-Consider: regenerative bone marrow response

Question 21

what is hypochromasia? When do we see it?

Answer 21

-More challenging to identify in dogs
-Consider: iron deficiency
i.e., dog with chronic blood loss entering stage of iron deficiency, impairing RBC production, causing pale RBCs to be released from the bone marrow

Question 22

what is basophilic stippling? When might we see it?

Answer 22

with wright’s stain
-consider Pb toxicity

Question 23

what are poikilocytes? When do we see them?

Answer 23

-General change in RBC morphology (size/shape) – many types
-Commonly seen in fragile iron deficient erythrocytes

Question 24

what is crenation and when do we see it?

Answer 24

-Spikey projections around RBC due to slow drying
-Could hide other features of the cell
-Could be pathologic but usually artifact

Question 25

what are acanthocytes and when do we see them?

Answer 25

-Long, irregular projections on RBCs due to abnormal composition of RBC membranes (classically have little 'beads' on the end of projections) -Consider: liver/spleen disease when abundant

Question 26

what are spherocytes and when do we see them? How are they created?

Answer 26

-Small dense cell with no central pallor (easier to identify in dogs) -Aren’t counted in RDW because they have the same volume as RBCs -Consider: Immune Mediated Hemolytic Anemia (IMHA) or transfused red cells -Created when macrophages selectively target the antibody-antigen complex on the RBC, after removal of that portion of the membrane in the spleen, the cell reseals more densely > less Hb -During transfusion, blood gets added from a bag that could’ve caused morphologic changes due to the fluid or anticoagulant

Question 27

what is a schistocyte and when do we see them?

Answer 27

Fragmentation of RBCs -Caused by shearing of RBCs by fibrin in circulation -Form of hemolysis -Consider: Disseminated Intravascular Coagulation (DIC)

Question 28

what is a microcyte and when might we see one?

Answer 28

-Small RBCs -Consider: Disseminated Intravascular Coagulation (DIC)

Question 29

what types of inclusions can we see in RBCs?

Answer 29

-parasites -bacteria -heinz bodies -howell-jolly bodies -nucleated RBCs

Question 30

what do bacteria look like in RBCs? What test should we follow up with if we detect this?

Answer 30

tiny blue structures on the surface or edge of the cell -can be hard to detect because they often look like stain precipitate -follow up with a PCR test

Question 31

what are heinz bodies? How can we best see them? When do they appear?

Answer 31

-Single projection on the periphery of an RBC >Areas of denatured hemoglobin >Better seen with NMB stain -Somewhat normal in cats because of their unique spleen >Concerning in anemic cats -Consider: oxidative damage/hemolysis (and anemia) >i.e., drugs, chemicals, toxins, acetaminophen in cats, onion/garlic in dogs, Zn toxicity from coins, Cu toxicity in sheep

Question 32

What are Howell-Jolly bodies? When do we see them and what do they mean?

Answer 32

-Nuclear remnant that was not ejected during differentiation -Usually removed by the spleen, but can be normal in cats -Non-specific pathologic indicator

Question 33

what are rubricytes? Where should they be? When might we find them in circulation?

Answer 33

-Immature, nucleated RBCs that should be in bone marrow -Present in certain disease circumstances >i.e., extramedullary hematopoiesis, 1˚ bone marrow disease

Question 34

What are target cells? What do they mean?

Answer 34

-A blip of hemoglobin in the center of a canine RBC -Consider: liver disease/neoplasia when abundant >Otherwise, non-specific

Question 35

What are eccentrocytes? When might we see them?

Answer 35

-RBC with peripheral white sections -Clearing of hemoglobin on the periphery of the cell -Consider: oxidative damage

Question 36

What are ghost RBCs? When might we see them? What else might we see along with them?

Answer 36

-White round cell marks -Consider: intravascular hemolysis >Plasma would likely be red due to free Hb (hemoglobinemia)

Question 37

what are dacrocytes and what should we consider if we see them?

Answer 37

-Tear drop shaped cells -Consider: myelofibrosis and other BM issues >Check the bone marrow!

Question 38

when do we see protein crescents on a blood smear?

Answer 38

if there is increased protein in the blood

Question 39

Which values will be low in a case of anemia?

Answer 39

RBC: presents on blood smear as more space between the RBCs Hgb HCT: used to classify severity

Question 40

What RBC issues can anemia be due to?

Answer 40

1. Decreased RBC production -At the level of the BM -Note that current cells will remain for the duration of their lifespan 2. Increased RBC loss -Cells removed from circulation by hemorrhage or hemolysis

Question 41

what are seven possible things that could lead to anemia?

Answer 41

1. renal failure 2. hemolysis 3. endocrine 4. neoplasia 5. inflammation 6. blood loss 7. iron deficiency

Question 42

How do we assess an anemia? What tools can we use to gather evidence?

Answer 42

History – acute or chronic? PE CBC Reticulocyte count – regen.? Total serum/plasma protein

Question 43

How do we characterize an anemia?

Answer 43

1. Severity -Defining severity is subjective and comes with experience based on HCT >Sometimes based on other analytes too! 2. MCV 3. MCHC 4. Regenerative/non-regenerative

Question 44

Broadly, what are the possible causes of regenerative anemia? How will these show in protein levels?

Answer 44

hemolysis or internal hemorrhage - normal or high protein >note that protein can also be influenced by inflammation and dehydration (appear higher) external hemorrhage - low protein

Question 45

broadly, what are the possible causes of non-regenerative anemia? What are the characteristics of each?

Answer 45

marrow disorder 1˚ -Disease arising in the bone marrow itself -Directly involved in the disease process -Multiple cytopenias 2˚ -A systemic disease impacting RBC production in the BM -Selective red cell depression

Question 46

what are the tell-tale signs of a regenerative anemia?

Answer 46

-Increased polychromasia/reticulocytes >increased anisocytosis; RDW >increased MCV; macrocytosis >decreased MCHC; hypochromasia -Increased neutrophils, platelets >Can have leukopenias still -Rubricytes cannot be the sole indicator of regenerative anemia >If there is no polychromasia, another explanation is required >Increased rubricyte count requires a corrected WBC count due to it counting nucleated cells >WBC – rubricyte count = corrected WBC

Question 47

what are the tell-tale signs of hemorrhage? What differences might we see between single site vs multiple site?

Answer 47

1. Anemia 2. Hypoproteinemia (with sufficient external blood loss) 3. Reticulocytosis – bone marrow shouldn't be impaired 4. Hypochromia (if chronic and external) >Due to loss of iron over time, leading to decreased hemoglobin Single sites = local problems -i.e., trauma, neoplasm Multiple sites = platelet and clotting factor issues -i.e., GI bleeding, blood loss in urine, hematomas