Erythrocytes aka RBC’s

Laboratory Procedures

Hematopoietic System

• Blood supplies cells with water, nutrients, electrolytes, and hormone. • Removes waste products

• Mainly CO2

• Cellular elements supply oxygen (RBC), protect against foreign organisms (WBC) and initiate coagulation (platelets).• Clotting factors

Blood Composition

• Separates into three components:• Red Blood Cells (RBC’s)• White Blood Cells and platelets (buffy

coat)• Plasma

• Bottom 1/3 to ½ of tube contains the heaviest of cellular material (the RBC’s).

Hematocrit=PCV (Packed Cell Volume)

• To determine hematocrit, whole blood is centrifuged to pellet the red blood cells.

• Plasma remains on the top of the red cells.• The fraction of blood that is packed is the

hematocrit and is read as a percentage.

Hemoglobin (Hgb)

• Normal values are usually 1/3 of the hematocrit.• Each hemoglobin molecule has 4 heme units

attached to globulins.• Abnormal heme groups, cannot carry oxygen.• Carboxyhemaglobin- Hgb has a higher affinity for

CO than O2.

• Bright red blood• Methemoglobin- The Fe molecule is oxidized to

Fe+3.• Blood becomes brown.• Tylenol toxicity in cats.

Red Blood Cells

• Function:• Carry oxygen to the tissues• Oxygen must be carried at enough

pressure to permit rapid diffusion of oxygen.

• The RBC is a vehicle for hemoglobin which is the carrier molecule for oxygen.

• The sigmoid shape of curve is a result of the cooperative binding from the 4 hemoglobin molecules.

Transport of oxygen in the blood

• 97% of oxygen transported from lungs to the tissues is carried in chemical combination with hemoglobin in RBC’s.

Erythropoiesis

• Production or Maturation of a RBC.• Only occurs in the bone marrow of normal

adult animals.• Occurs in the spleen and liver of the

fetus.• Maturation time usually takes 5 days.• Regulated by erythropoietin (EPO) which

is increased in the presence of hypoxia.• In most species, the kidney is the sensor

organ and major site of EPO.

Red Blood Cells (Erythrocytes)

• No nucleus due to have to fold and squeeze through tight spaces.

• Normocytes- cells look normal

Erythrocyte Life Span

• Dog- 110 days• Cat- 70 days• Cow- 160 days• Horse- 145 days• Man- 120 days• Mouse- 30 days

Erythrocyte Life Span

• Stem Cell → Rubriblast → Prorubricyte → Rubricyte →Metarubricyte→ Reticulocyte → RBC

• Metarubricyte- nucleated RBC releases in severe anemia.• No more mitotic division takes place

after this stage.• One rubriblast may give rise to as many as

8-32 RBC’s.

Normal Erythrocytes

• Morphologic features vary from species to species• Dogs: Biconcave disk shape with

central pallor• Cats: Generally round with little central

pallor.• Birds: Contain a nucleated RBC

Categories of Erythrocyte Characteristics

• 1. Cell arrangement on the blood film.• 2. Size• 3. Color• 4. Shape.• 5. Presence of structures on erythrocytes

Cell Arrangement on Blood Film• Rouleaux

• Rouleaux formation is a group of erythrocytes in stacks. This can be a sign of increased fibrinogen or globulin concentration.

• It can also be an artifact seen in blood that is held too long before preparing the blood slide or in blood that has been refrigerated.

Cell Arrangement Continued

• Agglutination• Agglutination, which

appears as rouleaux, occurs in immune-mediated disorders. An antibody coats the cell causing bridging or clumping.

• If you add a drop of saline to a drop of blood rouleaux formation will disperse and agglutination will not

Size

• Terms:• Anisocytosis:

• Variations in size• Can indicate anemia

• Macrocytosis:• Larger than normal cell size• Liver disease or Vitamin B12

deficiency• Microcytosis:

• Smaller than normal cell size• Iron deficiency

MCV

• Mean Corpuscular Volume• Describes cells as normocytic,

microcytic, or macrocytic. Calculates the average volume of rbc’s.

• MCV=(Hematocrit x 10)/RBC count in millions

• Normal: 66-77• (we will come back to this calculation

again)

Color

• Polychromasia:• Polychromatic erythrocytes exhibit a bluish tint. The tint is

due to a small amount nucleus retained in the cytoplasm. These are young cells and may appear as a reticulocyte

• Hypochromasia:• is a decrease in color, due to a decreased staining intensity

caused by insufficient hemoglobin within the cell. • Iron deficiency is the most common cause.

• Hyperchromasia:• refers to cell that appears darker than normal cells. This

gives the appearance that the cell is over saturated with hemoglobin. The erythrocyte has a fixed maximum capacity for hemoglobin and over saturation can NOT occur.

MCHC

• Mean Corpuscular Hemoglobin Concentration • describes cells as normochromatic or

hypochromatic.

• MCHC= (Hgb)/(Hct) x 100

• Normal is 31-36% • (we will come back to this calculation

again)

Polychromasia

Hypochromasia

Hypochromasia continued

• Hypochromatic should be differentiated from cells with the center “punched out”. A punched out appearance can be an artifact due to improper smear technique

Hyperchromasia

• True hyperchromasia does not exist.

Shape

• Poikilocytosis• Poikilocytosis is a major deviation in the

normal shape of the erythrocyte. The term poikilocytosis is an umbrella term that is used for any and all abnormally shaped erythrocytes and does not suggest a specific diagnosis

Schistocytes (Fragmented Cells)

• Also known as poikilocytes.• RBC’s with abnormal shape.• Formed as a result of shearing of the cell by fibrin

strands. This occurs when red blood cells rapidly pass through microvasculature that is lined or meshed with strands.

• They are observed in fragmentation hemolysis caused by DIC, vascular neoplasia, endocarditis, and possibly iron deficiency anemia.

Acanthocytes (Spur Cells)

• The term acanthocyte is derived from the Greek word “acanthi” meaning “thorn” Acanthocytes are cells with five to ten irregular, blunt, finger-like projections.

• The projections with vary in width, length and surface distribution. These cells are seen in animals with altered lipid metabolism such as cats with hepatic lipidosis or dogs with liver disease.

Acanthocytes Continued

Echinoctyes (Burr Cell)

• Echinocytes have multiple, small, delicate regular shaped spines evenly distributed around the cell and are indistinguishable from artificially crenated cells.

Echinoctyes Continued

• Echinocyte formation can be artificial, often seen with slow drying blood films or if the EDTA tube was underfilled. This artifact is then termed crenation.

• Echinocytes have been associated with renal disease, lymphosarcoma and rattlesnake bites in dogs.

• They can been seen after exercise in horses.

Crenation

• Identified as the presence of many irregular membrane projections involving most RBC’s.

• It is usually an artifact due to slow drying of the blood film.

• Commonly observed in pig blood but can be seen in any species.

Drepanocytes (Sickle cell)

• These cells are crescent shaped with pointed ends.

• Drepanocytes are often seen in normal blood of deer and goats. It is thought to be a result of low oxygen tension.

Drepanocytes

Keratocyte (Helmet Cells)

• Also called blister cells or bite cells. Keratocytes are associated with trauma especially cellular damage from contact with fibrin strands.

Prekeratocytes

• Cells with pseudovacuoles are called blister cells or pre-keratocytes.

Spherocytes

• Cells have a spheroid shape instead of the usual biconcave disk shape.

• Have reduced cell membrane and are hypochromatic.

• Seen most frequently in autoimmune hemolytic anemia (AIHA).

• Usually seen in dogs.

Stomatocytes

• The appearance of stomatocytes with their oval or rectangular central pallor has been compared to a smiling face, a fish mouth, and a coin slot.

• Stomatocytes are associated with a hereditary condition but are also seen in liver disease, acute alcoholism (humans), and electrolyte imbalances.

Target Cells and Folded Cells

• Two types of leptocytes observed mainly in dogs.

• Represent cells with an increases membrane-to-volume ratio not specific to any disease.

• The cell membrane is thin and flimsy.

Target Cells (Bull’s Eye Cells)

• Also called codocytes• Thin, bell-shaped cells• Centrally stained area• May be seen as

artifacts when smears

made in high humidity

or if blown dry.

Can indicate liver disease or hemoglobinopathies.

Target Cells

Anulocytes

• These are bowl shaped erythrocytes that form as a loss of membrane flexibility that does not allow the cell to return to a normal shape after passing through a capillary. They can occur due to lowed hemoglobin concentration or as an artifact.

Dacryocytes (tear drop cells)

• These tear drop shaped cells are seen in myeloproliferative diseases. These cells, when produced as an artifact can be identified by the direction of their tail.

• Dacryocytes produced as an artifact have their tails pointing in the same direction.

Nucleated Red Blood Cells (NRBC’s)

• Nucleated red blood cells (NRBC) usually represent early release of immature red blood cells during anemia.

• These are nuclear remnants seen in young erythrocytes during a response to anemia.

Basophilic Stippling

• Observed in RBC’s that contain abnormal aggregation of RNA.

• Can be observed in cases of heavy metal poisoning with non-regenerative anemias or intense erythrogenesis in dogs, cats, and ruminants.

Howell-Jolly Bodies

• Nuclear remnants observed in young erythrocytes.• Often observed in cats and horses.• Can be seen in regenerative anemic animals.• Also may be seen with splenic disease or in an animal

with the spleen removed.

Heinz Bodies

• Particles of denature hemoglobin protien.• They stain with new methylene blue and appear as

colorless bumps with quick stain.• May be caused by oxidant drugs and chemicals.

Also associated with onion toxicity in dogs!• Normal cat blood may have 2-3%.• Spleen recognizes as abnormal and starts to lyse

the cells.

Heinz Bodies

Reticulocytes

• These are immature red blood cells that contain organelles (ribosomes) that are lost in the mature cell. Cats have two forms of reticulocytes. • The aggregate form contains large

clumps of reticulum. They mature into the punctate form within 24 hours.

• The punctate form, unique to cats, contains two to eight singular granules. Punctate reticulocytes circulate for 7-10 days before the all the ribosomes are lost.

Reticulocytes in the Peripheral Blood

• Non-nucleated cell containing RNA which can be easily seen when stained with methylene blue.

• Hallmark of erythrocyte regenerative response.