Leukocytes: Structure, Function, and Classification

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Questions and Answers

What is the function of leukocytes in the immune response?

Secrete antibodies

Transport oxygen

Produce red blood cells

Recognize self from non-self antigens (correct)

Which type of stem cell gives rise to granulocytes and monocytes?

Granulocyte-monocyte progenitor

Common lymphoid progenitor

Multipotent hematopoietic stem cell

Common myeloid progenitor (correct)

What is the typical range for adult white blood cell (WBC) count?

$15 - 20$ x $10^9$/L

$4 - 10$ x $10^9$/L (correct)

$30 - 40$ x $10^9$/L

$1 - 5$ x $10^9$/L

Which of the following is NOT a determinant of the number of circulating leukocytes?

Nutritional intake Signup and view all the answers

During leukopoiesis, which pool involves division and maturation of precursor cells?

Proliferation pool Signup and view all the answers

How long does it take for a myeloblast to develop into a myelocyte?

3 to 6 days Signup and view all the answers

What is the average lifespan of neutrophils in the peripheral blood?

6 to 10 hours Signup and view all the answers

Which cytokines are responsible for the growth and differentiation of neutrophils?

GM-CSF, IL-3, G-CSF Signup and view all the answers

Where is the storage pool of mature neutrophils located?

Bone marrow Signup and view all the answers

Which of the following is NOT a stage in neutrophil development?

Basophil Signup and view all the answers

What is the last step in the process of neutrophil phagocytosis and killing of a microbe?

Granule releases its contents into the vacuole Signup and view all the answers

What is the main function of neutrophils in relation to undigested vacuole contents?

Exocytosis Signup and view all the answers

Which type of granules in neutrophils contains proteins like myeloperoxidase, lysozyme, and collagenase?

Primary (azurophilic) Signup and view all the answers

What is the main function of monocytes in immunity?

Phagocytosis Signup and view all the answers

Eosinophils release histaminase to:

Destroy parasites Signup and view all the answers

What is the main similarity between basophils and mast cells?

Contain histamine Signup and view all the answers

Where do lymphocytes develop from?

Common lymphoid progenitor Signup and view all the answers

Which type of lymphocyte plays a key role in generating antigenic specificity?

T-cells Signup and view all the answers

What is a likely cause of leukocytosis (>10.0 x 10^9/L)?

Infection Signup and view all the answers

What is a qualitative abnormality that can affect leukocytes?

Cytoplasmic abnormalities Signup and view all the answers

Which disorder can impact leukocyte structure and function?

Chediak-Higashi Syndrome Signup and view all the answers

Study Notes

Leukocytes

Developed from hematopoietic stem cells in the bone marrow (BM)
Go through differentiation and maturation before entering the circulation
Classified based on morphology: polymorphonuclear (PMN) and mononuclear (MN)

Functions of Leukocytes

Innate immunity: defend against infectious agents and foreign substances
Adaptive immunity: participate in specific immune responses

Granulocytes

Derived from granulocyte-monocyte progenitor (GMP) in BM
Cytokines responsible for growth and differentiation: GM-CSF, IL-3, and G-CSF
Stages of development: myeloblast, promyelocyte, myelocyte, metamyelocyte, band, and segmented neutrophil
Average lifespan: 6-10 hours in peripheral blood, several days in tissues

Neutrophils

First line of defense against foreign substances and microorganisms
Functions:
- Adhesion
- Diapedesis
- Migration
- Phagocytosis
- Killing and digestion
Granules: primary, secondary, and tertiary
Primary granules: contain myeloperoxidase (MPO), lysozyme, and bacterial permeability-increasing protein (BPI)
Secondary granules: contain lactoferrin, lysozyme, and collagenase
Tertiary granules: contain lysozyme and collagenase

Monocytes

Derived from granulocyte-monocyte progenitor (GMP) in BM
Cytokines responsible for growth and differentiation: GM-CSF, IL-3, and M-CSF
Stages of development: monoblast, promonocyte, and monocyte
Average lifespan: 20-40 hours in peripheral blood, then mature into macrophages in tissues
Functions:
- Innate immunity: phagocytosis and cytokine production
- Adaptive immunity: antigen presentation to T-lymphocytes

Eosinophils

Derived from eosinophil-basophil progenitor (EBP) in BM
Cytokines responsible for growth and differentiation: GM-CSF, IL-3, and IL-5
Average lifespan: 18 hours in circulation, 2-5 days in tissues
Functions:
- Parasitic infections: release histaminase to slow down hypersensitivity reaction
- Antigen presentation: promote proliferation of effector T cells

Basophils

Derived from eosinophil-basophil progenitor (EBP) in BM
Cytokines responsible for growth and differentiation: GM-CSF, IL-3, and IL-5
Average lifespan: 4 days in circulation
Functions:
- Allergic reactions: release histamine and other mediators
- Inflammation: involved in innate immunity

Lymphocytes

Derived from common lymphoid progenitor (CLP) in BM
Participate in adaptive immunity
Two types of adaptive immune response: humoral immunity and cell-mediated immunity
Subtypes: T-lymphocytes, B-lymphocytes, and natural killer (NK)-cells
Functions:
- T-lymphocytes: helper and cytotoxic
- B-lymphocytes: antibody production and antigen presentation
- NK-cells: innate immunity and tumor surveillance

Benign Leukocytes Disorders

Quantitative Abnormalities:
- Leukocytosis: >10.0 x 10^9/L in adults
- Leukopenia: <4.0 x 10^9/L in adults
Qualitative Abnormalities:
- Nuclear abnormalities: Pelger-Huët Anomaly
- Cytoplasmic abnormalities: toxic granulation and toxic vacuolization
- Adhesion defect: leukocyte adhesion deficiency
- Toxic changes: Döhle bodies and May-Hegglin Anomaly

Cytochemistry

Diagnosis and classification of acute leukemia
Study of chemical elements in cells: enzymatically or nonenzymatically
Stains:
- Myeloperoxidase (MPO)
- Sudan black B (SBB)
- Chloroacetate esterase (CAE)
- Nonspecific esterase (NSE)
- Periodic acid Schiff (PAS)
- Neutrophil alkaline phosphatase (NAP)
- Acid phosphatase (AP) and tartrate-resistant acid phosphatase (TRAP)

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Description

Learn about the structure, function, and classification of leukocytes, the white blood cells that protect the body from infectious agents. Explore how leukocytes develop from hematopoietic stem cells and the different types based on morphology and function.