Questions and Answers
Which type of granulocytic cell is known for its multilobed nucleus?
What is the primary role of eosinophils?
Defense against parasitic organisms
Basophils are phagocytic cells.
False
Mast cells, like circulating basophils, contain large numbers of cytoplasmic granules that contain __________.
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What is the primary function of dendritic cells?
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What distinguishes follicular dendritic cells from other dendritic cells?
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What is the process by which blood cells arise?
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What are the three basic properties of stem cells?
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Which cells are responsible for adaptive immunity?
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What are the categories into which cells of the immune system are divided?
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What is the major site of maturation for B lymphocytes?
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What do activated B cells differentiate into?
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T lymphocytes mature in the ______.
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The main difference between B cells and T cells is that B cells can bind to soluble antigens.
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Which type of T cell directly kills infected cells?
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Natural killer cells constitute what percentage of lymphocytes in humans?
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What is the function of macrophages?
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Macrophages can activate T cells during the immune response.
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What is opsonization?
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Study Notes
Immune System Overview
- Composed of various cells and organs with specific functions, crucial for defense against pathogens.
- Blood cells originate from hematopoietic stem cells (HSC) through hematopoiesis.
- Hematopoietic stem cells have three primary properties: self-renewability, cell division, and differentiation into diverse cell types.
Immune Cells Classification
- Immune cells are categorized into three broad groups:
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Lymphoid Cells: Responsible for adaptive immunity.
- B Lymphocytes
- T Lymphocytes
- Natural Killer (NK) Cells
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Mononuclear Phagocytes: Involved in engulfing and destroying microorganisms.
- Monocytes
- Macrophages
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Granulocytic Cells: Play roles in inflammation and response.
- Neutrophils
- Eosinophils
- Basophils
- Mast Cells
- Dendritic Cells
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Lymphoid Cells: Responsible for adaptive immunity.
Lymphoid Cells
- Comprise 20%-40% of body’s white blood cells and 99% of lymph cells, constantly circulating between blood and lymphatic systems, migrating to tissues.
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Subgroups based on function:
- B Cells: Have diverse receptors; produce antibodies.
- T Cells: Recognize antigens presented by MHC on other cells.
- NK Cells: Large granular lymphocytes with limited receptors but capable of targeting infected cells.
B Lymphocytes
- Mature primarily in bone marrow; each produces a specific antibody type.
- Expression of molecules on B cell membrane includes CD80, CD86 (costimulatory signals), CD40 (interaction with T cells), and B220 (marker).
- Upon antigen recognition, B cells activate and differentiate into plasma cells and memory B cells, with plasma cells producing antibodies.
T Lymphocytes
- Mature in the thymus; recognize MHC-presented antigens.
- Distinguished as helper T cells (CD4+) and cytotoxic T cells (CD8+).
- Helper T cells activate immune responses by releasing cytokines; cytotoxic T cells directly kill infected or cancerous cells.
- Memory T cells respond rapidly upon re-exposure to antigens.
Immune Response Types
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Humoral Immunity:
- Involves B cells producing antibodies against extracellular pathogens.
- Requires helper T cells for B cell activation and differentiation.
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Cell-Mediated Immunity:
- Involves T cells defending against intracellular pathogens.
- Helper T cells activate other immune cells; cytotoxic T cells induce apoptosis in target cells.
Natural Killer (NK) Cells
- Constitute 5%-10% of lymphocytes; target tumor and virus-infected cells.
- Lacks T cell receptors, but recognizes abnormalities (e.g., reduced MHC I expression).
- Use antibody-dependent cell-mediated cytotoxicity (ADCC) via CD16 receptor binding to IgG antibodies.
Mononuclear Phagocytes
- Include monocytes in blood and tissue-resident macrophages.
- Monocytes differentiate into macrophages after about 8 hours in circulation.
- Macrophages are categorized as fixed or free based on location, actively participating in phagocytosis and antigen presentation.
Macrophage Activation and Functions
- Activated by cytokines from T cells and a variety of stimuli, enhancing
- Phagocytic activity
- Secretion of inflammatory mediators
- Antigen presentation via increased MHC class II levels.
- Exhibit chemotaxis towards immune response-generated substances.
Phagocytosis Process
- Involves adherence of antigens, formation of phagosomes, fusion with lysosomes, and digestion of material.
- Antibody opsonization enhances phagocytosis by binding to antigens, making them more recognizable to macrophages.
Granulocytic Cells
- Classified as neutrophils, eosinophils, and basophils based on morphology.
- Neutrophils are the first responders at inflammation sites, playing a crucial role in acute responses.
- Eosinophils target parasites, while basophils release histamine and other substances involved in allergic responses.
Additional Points
- T suppressor (T regulatory) cells help regulate and suppress T cell activity to maintain immune balance.
- The ratio of T cells (approximately 2:1 CD4+ to CD8+) can indicate health status and immune response functionality.
- Activation of T-helper cells triggers the division into effector cells, influencing immune response dynamics through cytokine production.### Mast Cells
- Found in diverse tissues: skin, connective tissues of organs, mucosal epithelial tissue of respiratory, genitourinary, and digestive tracts.
- Contain numerous cytoplasmic granules filled with histamine and other active substances.
- Play a critical role alongside basophils in the development and propagation of allergic reactions.
Dendritic Cells (DCs)
- Named for long membrane extensions resembling nerve cell dendrites.
- Function primarily in the presentation of antigens to T helper (TH) cells.
- Utilize multiple mechanisms for antigen uptake: receptor-mediated endocytosis, phagocytosis, and macropinocytosis.
- Express high levels of class II major histocompatibility complex (MHC) molecules and co-stimulatory B7 family members.
Types of Dendritic Cells
- Four distinct types identified, each with unique functions.
Follicular Dendritic Cells (FDCs)
- Unique type not derived from bone marrow and lacks class II MHC expression.
- Do not perform antigen presentation.
- Located in lymph follicles within lymph nodes.
- Feature high levels of membrane receptors for antibodies, facilitating binding of antigen-antibody complexes.
- Enable B cells to bind to presented antigens through their B cell receptors (BCRs) during immune responses.
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Description
Test your knowledge about granulocytic cells and their functions with this quiz. Explore concepts such as the characteristics of eosinophils, basophils, and the unique roles of dendritic cells. Perfect for students studying immunology and cell biology.
