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Questions and Answers
Eosinophils are primarily responsible for defending against bacterial infections.
Eosinophils are primarily responsible for defending against bacterial infections.
False
Neutrophils are the first responders to any type of infection or wound.
Neutrophils are the first responders to any type of infection or wound.
True
Macrophages originate from monocytes and have roles in phagocytosis and antigen presentation.
Macrophages originate from monocytes and have roles in phagocytosis and antigen presentation.
True
The central lymphoid organs include the spleen and tonsils.
The central lymphoid organs include the spleen and tonsils.
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Dendritic cells do not migrate to lymphoid organs after capturing antigens.
Dendritic cells do not migrate to lymphoid organs after capturing antigens.
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Basophils are primarily involved in the defense against viral infections.
Basophils are primarily involved in the defense against viral infections.
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B lymphocytes mature within the thymus gland.
B lymphocytes mature within the thymus gland.
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Antibodies are produced by plasma cells, which develop from B lymphocytes.
Antibodies are produced by plasma cells, which develop from B lymphocytes.
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The major histocompatibility complex (MHC) class II molecules are expressed on the surface of macrophages.
The major histocompatibility complex (MHC) class II molecules are expressed on the surface of macrophages.
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T lymphocytes can produce antibodies in response to antigens.
T lymphocytes can produce antibodies in response to antigens.
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Langerhans cells are a type of dendritic cell found primarily in the bloodstream.
Langerhans cells are a type of dendritic cell found primarily in the bloodstream.
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Cytokines are produced by B lymphocytes to activate T lymphocytes.
Cytokines are produced by B lymphocytes to activate T lymphocytes.
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The debris from dead neutrophils contributes to the formation of pus.
The debris from dead neutrophils contributes to the formation of pus.
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The thymus gland serves as the site of development for T lymphocytes.
The thymus gland serves as the site of development for T lymphocytes.
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Lymphokines are a type of antibody produced by B lymphocytes.
Lymphokines are a type of antibody produced by B lymphocytes.
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Mucosa-associated lymphoid tissues are part of the central lymphoid organs.
Mucosa-associated lymphoid tissues are part of the central lymphoid organs.
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Cytotoxic T cells are primarily activated by binding to antigen with their T-cell receptor and exposure to cytokine from B lymphocytes.
Cytotoxic T cells are primarily activated by binding to antigen with their T-cell receptor and exposure to cytokine from B lymphocytes.
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Memory T cells play a crucial role in recalling an antigen during subsequent exposures to trigger a rapid immune response.
Memory T cells play a crucial role in recalling an antigen during subsequent exposures to trigger a rapid immune response.
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Natural killer (NK) cells require prior sensitization by antigens to effectively kill tumor cells.
Natural killer (NK) cells require prior sensitization by antigens to effectively kill tumor cells.
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Helper T cells assist in the activation of B lymphocytes by producing IL-4 and IL-5 cytokines.
Helper T cells assist in the activation of B lymphocytes by producing IL-4 and IL-5 cytokines.
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Regulatory T cells primarily enhance the immune response to eliminate microbial invaders more effectively.
Regulatory T cells primarily enhance the immune response to eliminate microbial invaders more effectively.
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Cytotoxic T cells predominantly recognize antigens presented on MHC class II proteins.
Cytotoxic T cells predominantly recognize antigens presented on MHC class II proteins.
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The activation of NK cells is solely dependent on activating receptor stimulation without any inhibitory signals.
The activation of NK cells is solely dependent on activating receptor stimulation without any inhibitory signals.
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Th1 T-helper cells primarily produce cytokines that activate cytotoxic T cells.
Th1 T-helper cells primarily produce cytokines that activate cytotoxic T cells.
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Study Notes
Immune System Overview
- The immune system is a complex network of cells, tissues, organs, and molecules that provide non-specific and specific protection against microorganisms, microbial toxins, and tumor cells.
- Lymphoid tissue and organs are categorized into central (primary) and peripheral (secondary) organs.
Central Lymphoid Organs
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Bone Marrow: Located in the central cavity of all bones, it's responsible for hematopoiesis (blood cell synthesis) and the proliferation of myeloid and lymphoid cells.
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Thymus Gland: A small gland behind the sternum, it's where T lymphocytes develop and mature into cytotoxic or helper T cells.
Peripheral Lymphoid Organs
- Lymph Nodes: Filter lymph fluid.
- Spleen: Filters blood and plays a role in immune responses.
- Other Lymphoid Tissues: Mucosa-associated lymphoid tissue (tonsils, adenoids, Peyer's patches), appendix, and lymphatic channels
Molecules of the Immune System
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Antibodies (Immunoglobulins): Proteins produced by plasma cells (activated B lymphocytes) with precise specificity for particular antigens.
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Lymphokines: Cytokines produced by T lymphocytes to regulate immune responses by signaling between cells.
Cells of the Immune System
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Lymphocytes:
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B Lymphocytes: Produced and mature in bone marrow, express membrane-bound antibody receptors. When activated, they differentiate into plasma cells to produce antibodies. They require two signals to become plasma cells (bind antigen and exposure to cytokines from T helper cells).
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T Lymphocytes: Produced in bone marrow, mature in the thymus. They do not produce antibodies but recognize antigens in a different way than B cells. They recognize peptide fragments of antigen complexed with cell surface MHC proteins. T cells can be further categorized into:
- Cytotoxic T cells (CD8+): Recognize antigens bound to MHC class I proteins, primarily on virus-infected cells. They produce cytotoxins to destroy infected cells.
- Helper T cells (CD4+): Crucial for both humoral and cellular immunity, recognizing antigens bound to MHC class II proteins. They release cytokines to stimulate other immune cells. They regulate and organize specific immune responses. Two subtypes: Th1 and Th2.
- Regulatory T cells (Treg): Suppress immune responses to prevent over-activity.
- Memory T cells: Remember antigens and initiate rapid responses if encountered again.
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Natural Killer (NK) Cells: Large granular lymphocytes that are cytotoxic in the absence of prior stimulation, killing virus-infected cells, tumor cells, and intracellular bacteria without needing antigen-specific activation. NK cell activation is determined by a balance of activating and inhibitory signals.
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Granulocytes:
- Neutrophils (PMNs): Phagocytic cells that respond to infection or injury and are the first responders.
- Eosinophils: Defend against parasitic infections.
- Basophils: Play a role in allergic responses.
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Monocytes: Migrate into tissues and differentiate into macrophages, which are phagocytic cells that engulf and eliminate pathogens and debris. They present antigen to T cells to initiate the specific immune response.
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Dendritic Cells: Phagocytic cells originating in bone marrow that present antigen to T lymphocytes to initiate the acquired immune response, crucial for initiating adaptive immunity
Antigen Presenting Cells
- Cells like macrophages, dendritic cells, and B cells present antigens to activate T lymphocytes to initiate an immune response
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