Basic Immunology: Immune Cells & Markers
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Questions and Answers

What is the fate of D.P-Thymocytes if they do not recognize and bind to MHC molecules?

  • They survive indefinitely.
  • They undergo isotype switching.
  • They differentiate into plasma cells.
  • They die within 3-4 days. (correct)

Which of the following surface markers is characteristic of B lymphocytes?

  • CD4
  • CD19 (correct)
  • TCR
  • CD3

Which types of antigens do T lymphocytes primarily recognize?

  • Nucleic acids
  • A wide variety of antigens
  • Polysaccharides and lipids
  • Only proteins in peptide form (correct)

Which cell type is responsible for humoral immunity?

<p>B lymphocytes (A)</p> Signup and view all the answers

What is the main function of natural killer (NK) cells?

<p>Kill virally infected and tumor cells (C)</p> Signup and view all the answers

What receptors do NK cells have that facilitate their function?

<p>Killer activation receptors (KARs) and Killer inhibition receptors (KIRs) (A)</p> Signup and view all the answers

How do positively selected T cells react when they bind strongly to self peptides?

<p>They undergo apoptotic death. (C)</p> Signup and view all the answers

Which type of white blood cell primarily responds to acute bacterial infections?

<p>Neutrophils (A)</p> Signup and view all the answers

What is a defining characteristic of basophils?

<p>Contain histamine and form 0-1% of WBCs (C)</p> Signup and view all the answers

Which cells are classified as antigen presenting cells (APC)?

<p>Monocytes (B)</p> Signup and view all the answers

What percentage of white blood cells do lymphocytes account for?

<p>Approximately 40% (B)</p> Signup and view all the answers

Which of the following T cell types is known as a helper T cell?

<p>CD4+ T cells (B)</p> Signup and view all the answers

Where do T lymphocytes mature before entering circulation?

<p>Thymus (C)</p> Signup and view all the answers

Which type of leukocyte is characterized by the presence of CD14 and CD40 markers?

<p>Monocytes (B)</p> Signup and view all the answers

Which leukocyte is mainly involved in allergic conditions and contains histamine?

<p>Basophils (A), Mast Cells (C)</p> Signup and view all the answers

Flashcards

B lymphocyte

A type of lymphocyte that matures in the bone marrow and plays a key role in humoral immunity. B cells recognize a wide range of antigens and differentiate into plasma cells, which produce antibodies.

T lymphocyte

A type of immune cell that develops in the thymus gland and plays a crucial role in cell-mediated immunity. T cells recognize specific antigens presented by MHC molecules on antigen-presenting cells and differentiate into effector T cells that directly attack infected or abnormal cells.

Positive Selection of T cells

Process by which immature T cells in the thymus are selected to survive based on their ability to recognize and bind to MHC molecules present on cortical epithelial cells. This ensures that only T cells with the potential to recognize self-MHC are allowed to develop.

Negative Selection of T cells

Process by which mature T cells in the thymus are eliminated if they bind too strongly to self-peptides presented by MHC molecules on medullary antigen-presenting cells. This prevents the development of T cells that could attack the body's own tissues.

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Natural Killer (NK) cell

A type of lymphocyte that lacks B cell receptors and is a key player in innate immunity. NK cells are effective in eliminating virally infected cells and tumor cells. They have two primary receptors: KAR (killing activation receptor) and KIR (killing inhibition receptor).

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Killer Activation Receptors (KARs)

Receptors on NK cells that recognize stress-related molecules expressed by virally infected cells and tumor cells, triggering the destruction of these cells.

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Killer Inhibition Receptors (KIRs)

Receptors on NK cells that recognize MHC class I molecules on host cells, preventing the NK cell from attacking healthy cells.

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Neutrophils

A type of white blood cell (WBC) that makes up the majority of WBCs in the blood. They are crucial for fighting acute bacterial infections.

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Eosinophils

A type of WBC that plays a key role in fighting parasitic infections and allergic reactions. Their granules contain enzymes that attack parasites.

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Basophils

A type of WBC that releases histamine, a chemical that contributes to allergic reactions and inflammation.

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Mast Cells

A type of WBC found in tissues, particularly in areas connected to the outside environment like the skin and mucous membranes. They release histamine and other inflammatory chemicals, leading to allergic symptoms.

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Monocytes

A type of WBC that circulates in the blood and differentiates into macrophages in tissues. They are important for engulfing and destroying foreign invaders and presenting antigens to other immune cells.

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Macrophages

A type of immune cell that develops from monocytes and resides in tissues. They are powerful phagocytes, engulfing and destroying foreign invaders. They also play a role in antigen presentation.

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T Cells (T Lymphocytes)

A type of WBC that matures in the thymus and plays a key role in adaptive immunity. They recognize specific antigens and coordinate immune responses. They have different subsets, including helper T cells and cytotoxic T cells.

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Study Notes

Basic Immunology: Immune Cells, Receptors & Markers

  • Lymphoid Tissues: Classified into primary and secondary organs
    • Primary organs: Thymus, bone marrow
    • Secondary organs: Neck (cervical) lymph nodes, armpit (axillary) lymph nodes, spleen, Peyer's patches, groin (inguinal) lymph node

White Blood Cell Classification

  • Myeloid Lineage:

    • Granular leukocytes: Neutrophils, eosinophils, basophils, mast cells
      • Neutrophils: ~60% of peripheral blood leukocytes; segmented (mature), band; activated in acute bacterial infection
      • Eosinophils: Eosin-loving granules, 0-5% of WBCs; activated in helminths infection and allergies
      • Basophils: Acidic cytoplasmic granules containing histamine; 0-1% of WBCs; activated in allergic conditions
      • Mast cells: Scattered in connective tissues (especially skin, mucosa, and epithelia); contain histamine; activated in allergic conditions; from granulocytic-myeloid cells
    • Agranular leukocytes: Monocytes, macrophages, dendritic cells
      • Monocytes, macrophages & dendritic cells: Monocytes in circulation, macrophages and dendritic cells in tissues; 5-7% of peripheral blood leukocytes; antigen-presenting cells (APCs); scavenger cells for innate immunity; Macrophage markers: CD14, CD40, CD11b

  • Lymphoid Lineage:

    • Granular leukocytes: Natural killer (NK) cells
    • Agranular leukocytes: T cells, B cells

Immune Cell Development

  • A pluripotent hematopoietic stem cell gives rise to all leukocytes, erythrocytes, and platelets.
    • This cell develops into myeloid and lymphoid lineages

T Lymphocytes

  • Thymus-derived cells: Arise from bone marrow, mature in thymus, enter circulation
  • Identified by presence of CD3 complex (TCR)
  • Four subsets:
    • CD4+ T cells (helper): recognize MHC class II
    • CD8+ T cells (cytotoxic): recognize MHC class I
    • CD4+ and CD25+ T regulatory (Treg)
    • T suppressor (Ts) cells

T Lymphocyte Selection

  • Double negative prothymocytes: Enter thymus; do not express CD4 or CD8; express TCR-CD3 complex, and both CD4 and CD8 (double positive cells; D.P).
  • Positive selection: DP thymocytes die unless they recognize and bind to major histocompatibility complex (MHC-I, II).
  • Negative selection: Positively selected T cells (CD4 or CD8) that bind strongly to self-peptides of the MHC I or MHC II on medullary APCs (phagocytes) undergo apoptotic death

B Lymphocytes

  • Bone marrow-derived cells: Arise and mature within bone marrow
  • Markers: B cell receptors (antibodies: IgM & IgD); CD19, CD20, & CD21 (complement receptor)
  • Two types:
    • B1: present in respiratory & GI systems
    • B2: widely distributed in lymphoid organs and tissues
    • Isotope switching is typical for B2 lineage
  • Plasma cells: terminally differentiated B cells; immunoglobulin-producing cells

Natural Killer (NK) Cells

  • Forms 5-10% of peripheral blood lymphocytes
  • Lack B cell receptor
  • Surface markers: CD16, CD56, and Fc receptor for IgG
  • Some NK cells carry TCR and CD4 or CD8 markers
  • Very active in killing virally infected cells and tumor cells
  • Have two major receptors:
    • Killing activation receptor (KAR)
    • Killing inhibition receptor (KIR)

Natural Killer Cell Receptors

  • Killer activation receptors (KARs): Recognize the presence of stress-related molecules expressed by virally infected cells and tumor cells.
  • Killer inhibition receptors (KIRs): Recognize the presence of MHC class I, which is normally displayed on the host cell surfaces.

Somatically Generated Receptors

  • T cell receptors (TCR): Associated with cluster of differentiation 3 (CD3); binds to antigen-MHC; CD4 and CD8 are co-receptors.
  • B cell receptors (BCR): Immunoglobulins IgM & IgD serve as B-cell receptors.

Summary Table (Lymphocytes)

Feature B Lymphocytes T Lymphocytes NK Cells
Origin Bone marrow Thymus Bone marrow
Percentage ~10-15% ~75-80% ~5-10%
Surface Markers CD19, CD20, CD21, CD35 CD3, CD4, or CD8 CD16, CD56, Fc receptor for IgG (some TCR)
Antigen Receptor B cell receptor (BCR), IgM, IgD T cell receptor (TCR), α and β chains KARs and KIRs
Antigen Recognition MHC-II, wide variety of antigens (proteins, polysaccharides) MHC-I and II, Peptide+MHC molecules on APC Stress-related molecules; MHC class I
Immunity Type Humoral Cell-mediated Cell-mediated

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Immune Cells, Receptors & Markers Lecture 3 PDF

Description

Explore the fundamentals of immunology with this quiz focused on immune cells, receptors, and lymphoid tissues. Learn about the classification and functions of various white blood cells and how they contribute to our immune response. This quiz is ideal for students studying basic immunology concepts.

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