Phagocytes and Their Functions

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Questions and Answers

What role does interferon gamma (IFNγ) play when secreted by NK cells?

It stimulates the production of cytotoxic T cells.

It protects nearby cells from viral infection. (correct)

It activates B cells to produce antibodies.

It enhances the ability of macrophages to ingest pathogens.

Which cells serve as the primary interface between the innate and adaptive immune systems?

NK cells

Dendritic cells (correct)

Macrophages

B cells

Which statement correctly defines T helper (Th) cells?

They activate B cells and macrophages for immune responses. (correct)

They are involved in the direct killing of virus-infected cells.

They primarily produce antibodies in response to antigens.

They represent the first line of defense against infections.

What is the primary function of B cells in the immune response?

Producing antibodies against foreign antigens. Signup and view all the answers

Which marker identifies T helper cells?

CD3+CD4+ Signup and view all the answers

How do CD8+ T cells acquire cytotoxic granules?

They develop them upon activation by cognate antigen. Signup and view all the answers

Which type of lymphocyte matures in the bone marrow?

B cells Signup and view all the answers

What is the main function of T regulatory cells (Tregs)?

To suppress excessive immune responses. Signup and view all the answers

What is the primary function of neutrophils?

Kill microbes Signup and view all the answers

Which component is specifically involved in opsonization?

Complement component C3b Signup and view all the answers

What role do macrophages play in the immune system?

Phagocytosis of pathogens Signup and view all the answers

Which type of cell is primarily responsible for immediate hypersensitivity reactions?

Mast cells Signup and view all the answers

How do NK cells function in the body?

Kill virus-infected cells Signup and view all the answers

What triggers the process of exocytosis in mast cells and basophils?

Stimulation by allergens Signup and view all the answers

What type of molecule do mononuclear phagocytes use to bind to opsonins?

Surface receptors Signup and view all the answers

What is the key difference between basophils and mast cells?

Basophils are primarily involved in late-phase allergic response Signup and view all the answers

What role do macrophages play in the interaction between innate and adaptive immunity?

They produce cytokines that help induce the adaptive immune response. Signup and view all the answers

What type of immunity do B lymphocytes primarily contribute to?

Humoral immunity by producing antibodies. Signup and view all the answers

How do complement components become activated in the context of immune responses?

Through both direct activation by microbes and antibodies. Signup and view all the answers

What is the primary function of cytotoxic T cells in the adaptive immune response?

They kill virus-infected body cells. Signup and view all the answers

What is the significance of cytokines and chemokines in the immune response?

They facilitate direct contact between innate and adaptive immune cells. Signup and view all the answers

What distinguishes T-cell dependent B cell activation from T-cell independent activation?

It generates memory B cells. Signup and view all the answers

What role do toll-like receptors (TLRs) play in B cell activation?

They provide a secondary response during T-cell independent activation. Signup and view all the answers

What is the primary function of plasma cells?

To produce and secrete antibodies. Signup and view all the answers

How do naive B cells recognize antigens?

By binding to soluble or membrane-bound antigens. Signup and view all the answers

Why do plasma cells have a high content of rough endoplasmic reticulum (RER)?

To support high levels of antibody production. Signup and view all the answers

What is the role of antigen-presenting cells (APCs) in T-cell activation?

They showcase antigens on MHC molecules for T-cell recognition. Signup and view all the answers

What triggers the expansion and differentiation of B and T cells during clonal selection?

The binding of antigens to receptors specific to those antigens. Signup and view all the answers

What is the significance of B cell receptors (BCRs) in the immune response?

They enable B cells to recognize and bind to specific antigens. Signup and view all the answers

Study Notes

Phagocytes

Phagocytes, including neutrophils and macrophages, function as specialized "eating" cells.
Neutrophils are mobile leukocytes that represent the majority of blood leukocytes and feature multilobed nuclei; also known as polymorphonuclear cells (PMNs).
Neutrophils contain granules with peroxidase, phosphatases, and defensins for microbial killing and respond to chemotactic factors released by microbes.
Macrophages are phagocytic cells derived from monocytes, with specialized versions in different organs and tissues.

Phagocytosis and Opsonization

Opsonization enhances the ability of phagocytes to engulf microbes by coating them with "opsonins."
Opsonins, such as C3b and antibodies produced by B cells, aid in microbe attachment and phagocytosis activation.
Mononuclear phagocytes use surface receptors to bind to opsonins, facilitating phagocytosis.

Mast Cells and Basophils

Mast cells are tissue resident cells crucial for immediate hypersensitivity reactions.
Basophils circulate in the blood but migrate to sites of allergic inflammation during late-phase responses.
Both cell types have large granules that release contents via exocytosis, which is vital for acute inflammatory responses.

Natural Killer (NK) Cells

NK cells are important in the defense against viruses and cancer and are found mainly in circulation.
They target infected cells by recognizing altered surface molecules, inducing apoptosis, and secreting interferon gamma (IFNγ) to protect nearby cells.

Dendritic Cells

Dendritic cells bridge the innate and adaptive immune systems, with membrane folds resembling nervous system dendrites for enhanced cell interaction.
They recognize microbial antigens and initiate adaptive responses by processing and presenting antigens to T-helper (CD4+) cells.

Adaptive Immune Cells

Lymphocytes, primarily T and B cells, develop in the thymus and bone marrow, respectively.
T cells include T helper (Th), T cytotoxic (Tc), and T regulatory (Treg) cells, with distinct functions and markers.
TCRs determine the specificity of T cells, while CD3 is essential for their activation.

T Helper and Cytotoxic T Cells

T helper cells activate B cells for antibody production and help cytotoxic T cells target infected cells.
Cytotoxic T cells (CD8+) require activation via specific antigens to acquire cytotoxic granules for targeting infected cells.

B Cells and Humoral Immunity

B cells function in humoral immunity by differentiating into plasma cells upon encountering antigens, producing antibodies.
Each B cell has unique antigen receptors to generate diversity for recognizing various environmental antigens.
B-cell activation can be T-cell independent (producing IgM and no memory B cells) or dependent (producing memory and plasma B cells).

Clonal Selection and Antigen Presentation

Clonal selection identifies B and T cells with receptors for specific antigens, stimulating their expansion.
B cells recognize native antigens, while T cells need antigens presented on MHC molecules by antigen-presenting cells (APCs), like dendritic cells and macrophages.

Interaction Between Innate and Adaptive Immunity

Innate and adaptive immune systems coordinate closely, responding to infections collaboratively.
Macrophages not only phagocytose pathogens but also produce cytokines that enhance adaptive responses.
Both immune systems interact through direct cell contact and signaling molecules, with T and B lymphocytes maturing under distinct influences and producing cellular and humoral immunity, respectively.

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Description

Explore the world of phagocytes, the specialized cells responsible for engulfing pathogens. This quiz covers the two main types of phagocytes: neutrophils and macrophages, their characteristics, and their roles in the immune response. Test your knowledge on how these cells contribute to microbial killing and inflammation.