Questions and Answers
Which granulocyte is most abundant in peripheral blood?
Which granulocyte is characterized by a bi-lobed nucleus and acidophilic granules?
What is the primary function of eosinophils?
Which cells are highly phagocytic?
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What chemicals do basophils release during hypersensitivity reactions?
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Which cell's nucleus is often obscured by specific granules?
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What is the primary function of dendritic cells in the immune system?
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What is another name for the reticuloendothelial system (RES)?
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Which of the following is NOT a function of dendritic cells?
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Where are interdigitating dendritic cells primarily found?
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Which statement is true about follicular dendritic cells?
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Which cell type is responsible for antigen presentation to T cells?
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What are the two arms of the immune response?
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What describes the innate response in the immune system?
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Which cells are the blood precursors of tissue macrophages?
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Which mechanism involves cytotoxic T cells and phagocytes?
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What characteristic is shared by both innate and adaptive immune responses?
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From where do mononuclear phagocytes originate and circulate as monocytes?
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What is the typical lifespan of a monocyte in the blood?
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Which of the following completes their maturation in the thymus?
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Study Notes
Cells of the Immune System
- Mononuclear phagocytes:
- Also known as reticuloendothelial cells
- Function in phagocytosis, production of inflammatory mediators, and presentation of antigen to T cells
- Mediate both innate and adaptive responses
Dendritic Cells
- Accessory cells that induce the adaptive response
- Two main types: interdigitating dendritic cells and follicular dendritic cells
- Found in most organs, epidermis of skin, and lymphatic tissue
- Thought to arise from marrow precursors related to mononuclear phagocytic system
- Functions: pick up antigens, transport them to lymph nodes, present antigen to T cells, and mediate adaptive responses
Granulocytes
- Contain abundant cytoplasmic granules
- Include neutrophils, eosinophils, and basophils
Neutrophils
- Multi-lobed (3-5 lobes) morphologically diverse nuclei
- Most abundant granulocyte (2.5-7.5 x 10^9/l)
- 12-15 µm diameter, life span 10 h (blood), days in tissues
- Highly phagocytic, key cells in anti-bacterial responses
- Mediate innate response and support adaptive responses
Basophils
- Basophilic granules
- Mediate hypersensitivity reactions through release of chemicals such as histamine
- 0.01-0.1 x 10^9/l, only occasionally seen in normal peripheral blood
- Nucleus obscured by basophilic specific granules
Eosinophils
- Bi-lobed nucleus and acidophilic granules
- 0.04-0.4 x 10^9/l, life span = 2 weeks
- Acidic-staining granules that bind eosin and stain orange
- Granules contain major basic protein
- Functions: elimination of infectious agents such as helminth worms, mediate hypersensitivity (allergic) reactions, and mediate adaptive responses
Mast Cells
- Dark basic staining granules containing heparin and histamine, stain purple
- Functions: support mast cells in tissues, mediate allergic reactions, and mediate adaptive responses
Introduction to the Immune System
- Immunology is the study of immunity
- Two arms to the immune response: innate response and adaptive response
- Innate response: first line of defense, non-specific, no memory
- Adaptive response: final stage of immune response, specific, memory
Mononuclear Phagocytes
- Originate in BM and enter the peripheral blood as monocytes
- Monocytes leave the circulation and enter tissues where they mature into macrophages (histiocytes)
- Functions: effector mechanisms utilized by innate and adaptive responses are the same
Effector Mechanisms
- Mechanisms by which harmful agents are destroyed by the immune system
- Can be both cell-mediated and humoral
- Examples: cytotoxic T cell, phagocyte, natural killer cell, complement, cytokines, acute phase proteins, and antibodies
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Description
Learn about the different cells of the immune system, their functions in phagocytosis, inflammation, and antigen presentation, and their roles in innate and adaptive responses.
