Cell Types and Immune Response

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Questions and Answers

What role do CD4 proteins play in immune response?

They attach T-cells to antigen presenting cells.

They serve as cytokine secreting helper cells. (correct)

They recognize peptides without MHC involvement.

They bind to MHC I molecules to kill infected cells.

What percentage of peripheral lymphocytes do mast cells constitute?

15-20%

20-25%

5-10% (correct)

1-3%

What is the primary function of CD8 proteins?

To destroy cells harboring microbes. (correct)

To enhance T-cell adhesion to APC.

To secrete antibodies in response to antigens.

To assist B lymphocytes in antibody production.

What surface molecule confers NK cells the ability to lyse IgG coated targets?

CD16 Signup and view all the answers

Which type of cell is responsible for producing antibodies within the immune system?

B-lymphocytes Signup and view all the answers

Which cells do not express TCR or immunoglobulins (Igs)?

Mast cells Signup and view all the answers

How are lymphocytes expressed in response to antigens?

By development of a specific clone of lymphocytes. Signup and view all the answers

What type of cells can NK cells kill without prior exposure to microbes or tumors?

Virus-infected cells and tumor cells Signup and view all the answers

What is a characteristic of integrins in T-cell function?

They attach T-cells to antigen presenting cells. Signup and view all the answers

Which of the following is NOT a component of the complement system?

CD16 Signup and view all the answers

What percentage of circulating lymphocytes typically express the CD8 protein?

30% Signup and view all the answers

What is the composition of lymphocytes specific for any single antigen before exposure?

Approximately 1 in 10 to 100,000 lymphocytes. Signup and view all the answers

Which receptor recognizes self MHC I molecules to inhibit NK cell activity?

Inhibitory cell receptor Signup and view all the answers

What cytokine do NK cells release to activate macrophages?

IFN-γ Signup and view all the answers

What do the majority of CD4-expressing cells function as?

Helper T cells. Signup and view all the answers

Which pathways are involved in the activation of plasma proteins in the complement system?

Mannose-binding and lectin pathways Signup and view all the answers

What distinguishes polyclonal lymphocyte proliferations from monoclonal lymphoid tumors?

Presence of unique DNA arrangements Signup and view all the answers

Which cell type is primarily responsible for initiating T-cell responses against protein antigens?

Dendritic cells Signup and view all the answers

What role do naive T cells play in the immune response?

Circulate through peripheral lymphoid organs Signup and view all the answers

Where are follicular dendritic cells primarily located?

In the germinal centers of lymphoid follicles Signup and view all the answers

What type of molecules do dendritic cells express to facilitate antigen presentation?

Major Histocompatibility Complex molecules Signup and view all the answers

What allows lymphocytes to migrate effectively during immune responses?

Concentration of antigens in peripheral lymphoid organs Signup and view all the answers

Which function is associated with plasma cells in the lymphoid organs?

Produce antibodies Signup and view all the answers

What is the primary function of receptors expressed by dendritic cells, such as TLRs and Lectins?

Capturing antigens Signup and view all the answers

Which cytokines are involved in stimulating the proliferation of NK cells?

IL-2 and IL-15 Signup and view all the answers

Which function is NOT performed by T-lymphocytes in innate immunity?

Providing signals for viral defense Signup and view all the answers

What is the role of danger signals in the context of innate immunity?

To stimulate the adaptive immune response Signup and view all the answers

Which of the following is true about the innate immunity system?

It recognizes broadly shared components of microbes Signup and view all the answers

Which T-lymphocyte type is primarily responsible for killing infected cells?

Cytotoxic T-lymphocyte Signup and view all the answers

What activates the killing and secretion of IFN-γ by NK cells?

IL-12 Signup and view all the answers

Which T-lymphocyte subtype inhibits immune responses to prevent reactions against self antigens?

Regulatory T-lymphocyte Signup and view all the answers

What type of immunity does not exhibit specificity for antigens?

Innate immunity Signup and view all the answers

What is the primary role of MHC molecules in the adaptive immune response?

To bind and present peptide fragments to T cells Signup and view all the answers

Which cells are responsible for presenting antigens to T cells?

Antigen presenting cells (APCs) Signup and view all the answers

Which class of MHC molecules is expressed on all nucleated cells?

Class I MHC Signup and view all the answers

What characteristic of MHC genes accounts for the variability among individuals?

Highly pleomorphic nature of MHC genes Signup and view all the answers

Which is a function of macrophages in the adaptive immune response?

Phagocytosing and processing antigens Signup and view all the answers

What do the a1 and a2 domains of Class I MHC molecules form?

A cleft for peptide binding Signup and view all the answers

What is a consequence of MHC's role in transplantation?

Evokes rejection of transplanted organs Signup and view all the answers

Where are peptides derived from proteins presented by Class I MHC molecules primarily generated?

Proteasomes Signup and view all the answers

Which type of immunity do macrophages participate in for the elimination of intracellular microbes?

Cell-mediated immunity Signup and view all the answers

Which organs are known as primary lymphoid organs?

Bone marrow and thymus Signup and view all the answers

Study Notes

Mast Cells

Comprise approximately 5-10% of peripheral lymphocytes.
Capable of producing inflammatory mediators.
Do not express T-cell receptors (TCR) or immunoglobulins (Igs).

NK Cells (Natural Killer Cells)

Larger cells containing abundant azurophilic granules.
Can kill virus-infected and tumor cells without prior exposure.
Identified by surface molecules, including CD16 (Fc receptor for IgG) which facilitates antibody-dependent cell-mediated cytotoxicity (ADCC).
Activity regulated by a balance of activating and inhibiting receptor signals.
Inhibitory receptors recognize self MHC I molecules, maintaining self-tolerance.

Plasma Proteins and Innate Immunity

Plasma proteins like complement system components are activated by microbes.
Activation pathways: alternative, lectin, and classical pathways.
Mannose-binding lectin and C-reactive protein also play roles in innate immunity.
Lung surfactants enhance phagocytosis of microbes.

Cytokines Influencing NK Cells

Key cytokines include IL-2 and IL-15 for proliferation, IL-12 for activation and IFN-γ secretion.

T-Lymphocytes Overview

Comprise three major populations:
- Helper T-lymphocytes: Activate B cells and other leukocytes.
- Cytotoxic T-lymphocytes: Kill infected cells.
- Regulatory T-lymphocytes: Limit immune responses and prevent autoimmunity.

T-Lymphocyte Activation

Develop in the thymus from hematopoietic stem cells.
Contain CD4 (60% of T-cells) that binds to MHC II and assists other immune cells.
Contain CD8 (30% of T-cells) that binds to MHC I to kill infected cells.
Integrins and CD28 play roles in adhesion and activation.

B-Lymphocytes

Only cells capable of producing antibodies, mediators of humoral immunity.
Mature in the bone marrow, constituting 10-20% of circulating lymphocytes.
Unique DNA rearrangements allow differentiation between polyclonal and monoclonal lymphocyte proliferations.

Dendritic Cells

Key antigen-presenting cells for T-cell activation.
Found in epithelia and interstitium, capturing antigens.
Express many receptors for antigen uptake and present antigens with MHC molecules.

Lymphocyte Recirculation

Lymphocytes continuously move between tissues and lymphoid organs.
Naive T cells must circulate to encounter antigens, while activated T-cells migrate to infection sites.
Plasma cells remain in lymphoid organs, producing antibodies.

Major Histocompatibility Complex (MHC)

MHC molecules display peptide fragments for T-cell recognition, essential for adaptive immunity.
Class I MHC expressed on all nucleated cells and platelets, crucial for recognizing intracellular antigens by CD8+ T cells.

Macrophages

Part of the mononuclear phagocyte system, crucial in the adaptive immune response.
Process and present antigens to T-cells, playing a key role in both cell-mediated and humoral immunity.
Act as effector cells in the elimination of intracellular pathogens.

Immune System Tissues

Divided into primary (central) lymphoid organs for lymphocyte maturation and secondary (peripheral) lymphoid organs for immune response initiation.

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Description

This quiz explores various cell types involved in the immune response, focusing on mast cells, NK cells, and other peripheral lymphocytes. It covers their characteristics, functions, and contributions to inflammation and defense against infections. Test your knowledge on the fundamentals of immunology and cellular functions.