CBC, Antibody Structure

Question 1

Understand the basic principles of flow cytometry.

Answer 1

Flow cytometry is has become a primary method for characterizing both normal and abnormal blood cells. Additionally automated hematology machines that perform the CBC are in large part flow cytometers.Flow cytometry is a method of cellular analysis that involves passing cells in single file past a probe of some sort. When a cell passes through a hole, it causes a voltage drop, and the size of the voltage drop is related to the size of the cell.

Question 2

Describe the things that should be scrutinized when a peripheral smear is examined.

Answer 2

Platelet clumps, WBC count, RBC characteristics, Abnormal white cells.

Question 3

Define and give the units for the hemoglobin (HGB) measurement.

Answer 3

HGB units are g per dL or g per L.

Question 4

Define and give the units for the hematocrit (HCT) measurement.

Answer 4

HCT may be expressed as a percentage (e.g. if the HCT is 50%, then 50% of the whole blood volume is occupied by red cells), or in terms of liters per liter (e.g. a HCT of 0.5L/L means that there are 0.5 L of red cells per 1.0 L of whole blood).

Question 5

Given the red blood cell count (RBC), the HGB (hemoglobin) and the HCT (hematocrit) be able to calculate the MCV (mean cell volume), MCH (mean cell hemoglobin), and the MCHC (mean cell hemoglobin concentration).

Answer 5

Mean cell volume: MCV = (HCT ÷ RBC) X 10.Mean cell hemoglobin: MCH = (HGB ÷ RBC) X 10.Mean cell hemoglobin concenctration: MCHC = (HGB ÷ HCT) X 100

Question 6

Define the MCV, the MCH, and the MCHC and relate these definitions to the units for these indices.

Answer 6

The MCV is the mean size of the red cells counted, units femtolitresMCH: This parameter is not used all that frequently since it parallels the MCV – MCV goes up or down, MCH goes up or down. Units: picograms (10-12g).MCHC: MCHC is the average concentration of hemoglobin in red cells. Units: g/dL or L

Question 7

Describe how the MCHC, MCV, and the MCH are used (or not used) in evaluating a patient’s red blood cells.

Answer 7

MCHC: Its value decreases in moderate to severe microcytic anemia. However an increased value is only seen in hereditary spherocytosis. An increased MCHC can also be the result of in vitro hemolysis.In patients with anemia, it is the MCV measurement that allows classification as either a microcytic anemia (MCV below normal range), normocytic anemia (MCV within normal range) or macrocytic anemia (MCV above normal range).MCH value is diminished in hypochromic anemias

Question 8

Describe the cause of platelet clumping and what should be done when platelet clumping is suspected as the cause of a spuriously low platelet count.

Answer 8

EDTA interaction can sometimes cause platelet clumping. Look at the peripheral blood smear to confirm the presence of a clump. Use a different anticoagulant (Sodium citrate) to get a better platelet count next time.

Question 9

Describe the advantages and disadvantages of a manual white blood cell differential. Describe the advantages and disadvantages of an automated white blood cell differential.

Answer 9

The automated methods are very good at recognizing normal blood cells. When normal blood cells are enumerated, the differential results are also more statistically accurate since the machine can count thousands of cells rather than hundreds of cells.If abnormal cells are encountered the machine is programmed to tell the operator, “I think I see a blast (or whatever). You look at a peripheral smear and confirm it.”

Question 10

Be able to identify normal white blood cells in a peripheral smear.

Answer 10

See Blood Cell Types iFliprs.

Question 11

What is the H chain?

Answer 11

The immunoglobulin H (heavy) chain is the large polypeptide subunit of an antibody (immunoglobulin).There are five types of mammalian Ig heavy chain denoted by the Greek letters: α, δ, ε, γ, and μ.The type of heavy chain present defines the class of antibody; these chains are found in IgA, IgD, IgE, IgG, and IgM antibodies, respectively.

Question 12

Please tell me about L chains.

Answer 12

A L (light) chain has two successive domains: one constant domain and one variable domain. The approximate length of a light chain is 211 to 217 amino acids.Each antibody contains two light chains that are always identical; only one type of light chain, κ or λ, is present per antibody in mammals.

Question 13

What are kappa and lambda chains?

Answer 13

The two types of light chains.

Question 14

What is the hinge region?

Answer 14

It attaches the arms of the Y to the base and allows some flexibility.

Question 15

What is the Fab?

Answer 15

Fragment antigen binding region of antibody; the arms of the Y

Question 16

What is F(ab)2?

Answer 16

2 Fabs together. Fab is univalent, F(ab)2is divalent.

Question 17

What is Fc?

Answer 17

Fragment crystallized region of antibody; the base of the Y

Question 18

What are complementarity-determining regions?

Answer 18

CDR’s are antibody or T cell receptor regions where the molecule complements an antigen’s conformation. Thus, CDRs determine the molecule’s specificity and make contact with a specific antigen.

Question 19

What are hypervariable regions?

Answer 19

Amino acid sequence variability is not distributed uniformly along the V domain; most of the variability is in 3 areas called, therefore, hypervariable regions

Question 20

What are variable (V) and constant (C) domains?

Answer 20

Constant regions are made up of 1 (in L chains) to 4 (in epsilon and mu) compact, structurally-similar domains called C domains. Each chain also has, at its N-terminal (conventionally shown on the left), a domain that is different in sequence between antibodies of different specificities: the variable domain.

Question 21

What are VL and CL?

Answer 21

Variable and constant domains on light chains.

Question 22

What are VH and CH?

Answer 22

Variable and constant domains on heavy chains.

Question 23

Name the 5 antibody classes, and their characteristic heavy chains.

Answer 23

There are five types of mammalian Ig heavy chain denoted by the Greek letters: α, δ, ε, γ, and μ. The type of heavy chain present defines the class of antibody; these chains are found in IgA, IgD, IgE, IgG, and IgM antibodies, respectively.

Question 24

Distinguish the 5 immunoglobulin classes in terms of size, and for IgG, IgM and IgA, their approximate concentration in serum.

Answer 24

IgG: 150,000 kD, E: 190,000, D:180,000, A:400,000, M: 900,000IgG: 1000 mg/dL (dL = 100 mL),IgA: 200 mg/dL,IgM: 100 mg/dL

Question 25

Describe the structure of antibody combining sites.

Answer 25

The portion of an antibody molecule that makes physical contact with the corresponding antigenic determinant + the portion of an antigen that makes physical contact with the corresponding antibody = antibody binding site.

Question 26

Explain why complementarity-determining regions are also called hypervariable regions.

Answer 26

This is where there is the most variation in AA sequence because it is binding a very specific antigen.

Question 27

Give an example of a class, a subclass, an allotype, an idiotype.

Answer 27

Class: Ig G,A,M,D,E Subclass: IgG1,2,3,4There are minor allelic differences in the sequence of immunoglobulins between individuals, just as blood types or eye color differ. These differences are called allotypes,Each antibody will have its unique combining region, made up of the CDR amino acids of its L and H chains; we can call this unique structure an idiotype (idio means self).