Stem Cells Overview

Questions and Answers

What characterizes Natural Killer cells in contrast to B and T lymphocytes?

They typically produce antibodies.

They are differentiated by their size alone.

They are difficult to differentiate morphologically. (correct)

They express TCR on their surface.

Where do B-lymphocytes mature in mammals?

Bursa fabricus

Spleen

Thymus

Bone marrow (correct)

Which type of T-lymphocyte expresses CD4 on its surface?

T Helper cells (correct)

Memory cells

T cytotoxic cells

Natural Killer cells

What type of antigen complex do T cytotoxic lymphocytes (TC) recognize?

Antigen-MHC1 complex Signup and view all the answers

Which type of T Helper cell secretes IL-17?

T Helper Type 17 cells Signup and view all the answers

What is the primary function of Cytotoxic T-Lymphocytes (CTL)?

To directly eliminate infected or cancerous cells. Signup and view all the answers

Which cells are primarily responsible for regulating lymphocyte activity through cytokine secretion?

Eosinophils Signup and view all the answers

What is the primary distinction between inflammatory monocytes and patrolling monocytes?

Inflammatory monocytes enter tissue in response to infection, while patrolling monocytes act as a reservoir along blood vessels. Signup and view all the answers

What is the main function of macrophages in tissues?

To repair and regenerate tissue as well as engulf pathogens Signup and view all the answers

Which type of cells acts as the most efficient activator of T cells?

Dendritic cells Signup and view all the answers

Which of the following best describes myeloid antigen-presenting cells?

They act as a bridge between innate and adaptive immunity. Signup and view all the answers

Eosinophils are known to contribute to which of the following conditions?

Asthma Signup and view all the answers

What unique characteristic do dendritic cells have compared to other myeloid derived cells?

They have large membranous extensions that increase surface area. Signup and view all the answers

Which of the following is NOT a function of macrophages?

Produce antibodies Signup and view all the answers

What is the primary characteristic of embryonic stem cells?

They are pluripotent cells capable of generating any cell type in the organism. Signup and view all the answers

Which of the following stem cells is responsible for producing all types of blood cells?

Hematopoietic stem cells Signup and view all the answers

What defines the role of common myeloid progenitors (CMP)?

CMP can generate various cell types in the myeloid-erythroid lineage. Signup and view all the answers

During an infection, which type of cell is the dominant first responder?

Neutrophils Signup and view all the answers

What process involves the differentiation of hematopoietic stem cells into various blood cell types?

Hematopoiesis Signup and view all the answers

Which statement about basophils is true?

They contain large granules filled with basic proteins and play a role in vasodilation. Signup and view all the answers

What is the function of neutrophils during an infection?

They participate in tissue remodeling and release antimicrobial proteins. Signup and view all the answers

Which type of stem cell can only differentiate into specific cell types of a particular tissue?

Adult stem cells Signup and view all the answers

What is a primary function of T Regulatory Lymphocytes (TREG)?

Inhibit an immune response Signup and view all the answers

Which surface markers are associated with Natural T Regulatory cells?

CD4 and CD25 Signup and view all the answers

Where do Natural T Regulatory Lymphocytes (TREG) originate?

During maturation in the Thymus Signup and view all the answers

How do Natural Killer (NK) cells recognize abnormal cells?

By recognizing the absence of MHC-1 molecules Signup and view all the answers

What characterizes NKT cells?

They share features of both T cells and NK cells. Signup and view all the answers

What is the role of cytotoxic granules in NK cells?

They help to kill abnormal cells. Signup and view all the answers

Study Notes

Stem Cells

Stem cells possess abilities to self-renew and differentiate into diverse cell types.

Types of Stem Cells

Embryonic Stem Cells: Pluripotent, able to generate all cell types in an organism.
Adult Stem Cells (Somatic): Found in specific organs, differentiate only into cell types of that tissue.
- Examples: Hematopoietic Stem Cells (HSC) in blood, Mesenchymal Stem Cells (MSC) in bone marrow.

Hematopoietic Stem Cells (HSC)

Differentiates into all blood cell types; less than 1 in 500,000 bone marrow cells.
Generally quiescent but can proliferate significantly when required.
Hematopoiesis: The process by which HSCs differentiate into various blood cells.
Hematopoiesis rates depend on the surrounding environment.

Human Blood Corpuscle Types

Two lineage paths: Common Myeloid Progenitor (CMP) and Common Lymphoid Progenitor (CLP).

Myeloid-Erythroid Lineage

First responders to infections.
CMP Differentiation:
- Erythroid Progenitor:
  - Generates Erythrocytes (red blood cells) and Platelets.
- Myeloid Progenitor:
  - Differentiates into Granulocytes (Neutrophils, Basophils, Eosinophils, Mast cells) and Myeloid Antigen Presenting Cells (Monocytes, Macrophages, Dendritic cells).

Granulocytes

Neutrophils:
- Lifespan of a few days; primary responders during infections; increased number seen during leukocytosis.
- Kills pathogens through phagocytosis and antimicrobial protein release.
Basophils:
- Contain granules with histamine; involved in allergic reactions; releases cytokines.
Mast Cells:
- Found in various tissues; similar functions to basophils; released undifferentiated, differentiate in blood.
Eosinophils:
- Phagocytotic and cytokine-secreting cells; important in defense against multicellular organisms; involved in asthma and allergy responses.

Myeloid Antigen-Presenting Cells

Phagocytic cells capable of antigen presentation, bridging innate and adaptive immunity.

Monocytes

Heterogeneous, differentiate into various tissue resident cells.
Two categories: Inflammatory (enter tissue during infection) and Patrolling (resident along blood vessels).

Macrophages

Tissue-resident monocytes involved in tissue repair and regeneration.
Can also act as inflammatory macrophages and antigen-presenting cells (APC).

Dendritic Cells

Arise from both myeloid and lymphoid lineages; most efficient at activating T cells.

Cells of Lymphoid Lineage

Lymphocytes play a central role in adaptive immunity; make up 20-40% of circulating blood lymphocytes.

Types of Lymphocytes

Subdivided into B cells, T cells, and Natural Killer (NK) cells; differentiated by surface proteins (Cluster of Differentiation - CD).

B-Lymphocytes

Mature in the bone marrow (mammals) and Bursa fabricus (birds).
Differentiate into Plasma cells (secrete antibodies) and Memory cells.

T-Lymphocytes

Mature in the thymus; express T-cell receptors (TCR).
Differentiated into T-helper cells, T-cytotoxic cells, and T-regulatory cells.

T Cytotoxic Lymphocytes (TC)

Express CD8 recognizing antigen-MHC1 complex; eliminate infected, cancer, or foreign graft cells.

T Helper Lymphocytes (TH)

Express CD4, recognizing antigen-MHCII; further differentiated into TH1, TH2, TH17, and T follicular Helper Cells involved in B cell development.

T Regulatory Lymphocytes (TREG)

Inhibit immune responses; identified by CD4, CD25, and FoxP3 expression.

Natural Killer Cells (NK)

Part of innate immunity with non-specific receptors; account for 5-10% of circulating lymphocytes.
Target abnormal cells by recognizing absent MHC-1 on cell surfaces and expressing receptors for immunoglobulins.

NKT Cells

Share traits of T cells and NK cells; express TCR, recognize specific lipids/glycolipids on CD1, and release cytotoxic granules.

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Description

Explore the fascinating world of stem cells, including embryonic and adult stem cells. Learn about their unique properties, their ability to self-renew, and their differentiation potential into various cell types. This quiz covers key concepts such as hematopoietic stem cells and the processes of dedifferentiation and trans-differentiation.