3.17.14* Structure and Function of Blood Cells Flashcards
PPT* Lecture Notes* Reading (pp. 15-32, 109-111 (granulocytes/monocytes), 127-130 (lymphocytes))* Powerpoint
What are the characteristics of eosin stain?
aromatic/acidic (negatively charged)
soluble in ethanol, NOT water
What cell types need eosin stain to visualize?
RBCs
Eosinophils
Order white blood cell subtypes by prevalence in PBS
neutrophils (40-70%) lymphocytes (20-30%) (T cells, then B cells and NK cells) monocytes (3-8%) eosinophil (5%) basophils (<1%)
When do eosinophil counts increase
during allergic reactions and parasitic infections
What is methylene blue stain used to visualize?
basophils
What are the characteristics of methylene blue stain?
aromatic/basic (positively charged)
soluble in water or methanol
what does methylene blue stain bind?
hydrophobic acidic macromolecules (nucleic acids, some proteins)
Functions of basophils?
degranulate in allergic reactions (related to tissue mast cells)
Functions of neutrophils?
a. For bacterial infections (phago, degranulation, formation of extracellular traps NETS)
b. Lifespan 1 day
What cell type increases with bacterial infection?
neutrophils. May increase 10x.
What cell type increases with viral infection?
lymphocytes
Function of monocytes?
a. monocytes are phagocytes that present foreign antigens via MHC II
b. precursor to most tissue macrophages
What are the types of granulocytes?
…
Mononuclear cells are
lymphocytes or monocytes
reactive lymphocytes
often angulated, these are the forms that increase during viral infection
large granular lymphoctes
NK cells and CD8 cells
what are the causes of increased platelet counts?
iron deficiency
What are the functions of platelets?
a. primary hemostatic plug (aggregation)
b. stimulate coagulation cascade (fibrin clot formation/clot retraction)
c. stimulate wound healing (fibroblast growth/migration)
d. immune function (antigen presentation, release platelet factor 4 cytokine (PF4) that can kill some pathogens
neutrophil variants seen in bacterial infections “shift to the left”
a. bands (look like horseshoe)
b. metamyelocytes (kidney bean nucleus)
c. myelocytes (rounded nuclei)
d. toxic granulation (blue primary granules seen in early myeloid precursors in the bone marrow, pink granules are called secondary granules)
“shift to the left”
when during an infection (mostly bacterial), neutrophils are released into peripheral blood earlier than they normally would
What causes shift to the left?
bacterial infection
neoplastic
What happens when hemoglobin is oxidized?
-SH groups become crosslinked. Results in denaturation and/or precipitation
What is the name of Hb with oxidized iron (Fe 3+)?
methemoglobin
What enzyme is responsible for reducing methemoglobin to hemoglobin?
cytochrome b5 reductase with glutathione
What molecule on RBC surface removes complement?
DAF (decay accelerating factor)
anisocytosis
abnormal sizes of cells
poikilocytosis
abnormal RBC shapes
?polychromasia
RBC showing residual mRNA with methylene blue
What causes sickle cell disease
substitution at sixth amino acid in beta globin (glutamic acid to valine).
What are bite cells
Tissue-based phagocytes can do damage repair on oxidized (precipitated) hemoglobin, removing chunks of the cell, resulting in “bite” cells. Characteristic of G6PG deficiency.
Schistocytes
RBC fragments; characteristic of microangiopathic hemolytic anemias (small blood vessels).
How do you measure Hct?
a. divide red cell volume by total blood volume, you will get a percentage of the blood that is occupied by red cells
b. RBC count times red cell volume
serum
The supernatant of clotted blood
Laboratory testing of clotting mechanisms requires serum or plasma
plasma
How is hemoglobin measured
a hematology analyzer uses spectrophotometry to quantify color emitted (with cyanide) that correlates with hemoglobin level
What dye is used for spectrophotometry in a hematology analyzer of reticulocytes?
methylene blue, which binds to RNA and emission correlates with reticulocytes as fraction of RBCs in a give specimen
What does a coulter chamber measure?
a. with direct current: number of cells
b. alternating current: number of large particles in a cell (useful for WBCs)
MCV (mean red cell volume)
..
Patients with accelerated RBC production will have higher or lower MCV?
higher, because RBC precursors are larger
What is the MCH (mean cell hemoglobin)
The hemoglobin measure per RBC count
What is the MCHC (mean cell hemoblobin concentration?
The hemoglobin measure divided by the hematocrit
What does a hematology analyzer measure directly?
Hemoglobin Red cell count (RBC) Mean red cell volume (MCV) Red cell distribution width (RDW) Platelet count Mean platelet volume (MPV)
NOT
Hct
MCH
MCHC
How do you measure WBCs?
a. lyse RBC in sample
b. pass through coulter chamber (measures size and complexity and plot
What cell types are hard to distinguish between with a hematology analyzer?
eosinophils and basophils
What does a flow cytometer do?
Measures laser deflection (forward scatter) which can tell size/shape to better separate granulocyte population
immature platelets
have excess RNA, unknown significance
the immature platelet fraction will go UP in patients whose thrombocytopenia (bone marrow failure) is due to impaired production
In patients whose thrombocytopenia is due to rapid consumption, it will also go up – but, we think, it will go up more.
Summaries the processes within the hematology analyzer
The lab runs an EDTA-anticoagulated blood specimen (the tubes usually have a purple top) through a “hematology analyzer”, which performs several functions. It uses a color-generating reagent (usually cyanide) and a spectrophotometer to measure the total hemoglobin (Hgb). Spectrophotometry is the most common method used to measure reticulocytes as well (via a different color-generating reagent). Most analyzers then pass the cells at a constant rate through a small aperture across which a voltage gradient is placed. The voltage changes as the aperture is partially occluded, and the change (translated into “impedance”) is precisely proportional to the volume of the cell. This conductivity method generates the red cell count (RBC) and a distribution (usually bell shaped) of cell volumes. From the latter it derives the mean cell volume (MCV) and the width of the bell shaped curve (the red cell distribution width, or RDW). From those numbers it calculates the mean cell hemoglobin (Hgb per cell) and mean cell hemoglobin concentration (hemoglobin per unit intracellular volume). In addition to red cells, it counts a population of smaller objects and, on the basis of size only (again, via conductivity), generates the platelet count for which it also generates a mean platelet volume (MPV). Finally, it mixes a portion of the sample with a reagent that lyses red cells, and counts the remaining white cells (WBC) by at least two simultaneous conductivity methods. In addition to the conductivity (also called “impedance”) methods just described, most analyzers pass the cells through a laser and measure the light generated at one or more angles off the beam. That method is called flow cytometry.
Bands
immature granulocytes/neutrophils
What are bands measured as?
neutrophils
Blasts
early blood cell precursors
What are blasts measured as?
lymphoctes or monocytes
RBC fragments usually measured as?
platelets
What is the issue with platelet clumps?
May suggest artifactual thrombocytopenia. Try using citrate instead of EDTA
Where is erythropoetin produced?
the peritubular interstitial cells of the kidney, and 10% in the liver. No preformed stores. Production stimulated by O2 tension in kidney.
What is the structure of hemoglobin
Each molecule of normal adult haemoglobin A (Hb A) (the dominant haemoglobin in blood after the age of 3–6 months) consists of four polypeptide chains, α2β2, each with its own haem group.
what are the types of hemoglobin
HbA; a2B2
HbA2 ; a2Y2
HbF ; a2d2
Reduced ATP production from glycolysis in red cells would result in which of the following?
a. reduced intracellular hemoglobin levels
b. impaired mitochondrial function
c. increased complement fixation
d. red cell lysis
D, due to deficient offset of osmotic pressure
A patient whose red cells have an impaired ability to regenerate glutahione might show with of the following on her peripheral blood smear?
Bite cells. Cross-linked sulfate side chains. They get bit by macrophages and make a bite cells. Also iron itself can be oxidized (methemaglobin).
dacrocytes
…
Which of the following cells cannot be counted by a hematology analyzer?
a. sickle cells
b. bite cells
c. hypochromic cells
d. nucleated red cells
e. a, b, c
E.
These cells types can only be seen in PBS.
What the hematology analyzer doesn’t count reliably
bands; counted as neutrophils
blasts: counted as lymphocytes or monocytes
red cell fragents: counted as platelets
platelet clumps: can result in artifactual thrombocytopenia
