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Questions and Answers
Where do antigen-presenting cells (APCs) display antigens for recognition by T cells?
What is the main function of effector T lymphocytes at peripheral sites of infection?
Where do plasma cells primarily remain to secrete antibodies?
Where are naive lymphocytes primarily searching for foreign antigens?
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What is the main role of peripheral (secondary) lymphoid organs?
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What is the primary function of antigen-presenting cells (APCs) with respect to microbes?
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Where do effector T lymphocytes migrate to function in eliminating infectious microbes?
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What distinguishes the functions of naive lymphocytes from effector T lymphocytes?
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Study Notes
Adaptive Immune System
- Comprises lymphocytes with diverse receptors specific to foreign substances.
- Antigens are molecules recognized by lymphocytes or antibodies.
Innate vs. Adaptive Immunity
- Innate immunity provides immediate defense against infections through mechanisms like epithelial barriers and phagocytes.
- Adaptive immune responses develop later, mediated by lymphocytes, with antibodies blocking infections and T lymphocytes targeting intracellular pathogens.
Immune System Cell Distribution
- Immune cells are located in various tissues and perform specific host defense roles.
- Most immune cells are derived from bone marrow and circulate in the blood as leukocytes (white blood cells).
Lymph Nodes
- Act as filters for lymph, where antigen-presenting cells (APCs) sample antigens from microbes.
- Dendritic cells transport antigens from epithelial tissues to lymph nodes, concentrating microbial antigens for immune responses.
Spleen
- A vascularized organ that processes blood-borne antigens similar to lymph nodes' role with lymph-borne antigens.
- Blood flows through a network of channels, allowing dendritic cells and macrophages to capture and concentrate antigens.
- Contains phagocytes that destroy microbes and old red blood cells.
Cutaneous and Mucosal Immune Systems
- Specialized lymphoid tissues and APCs are present in skin and mucosal barriers (gastrointestinal and respiratory tracts).
- Immune cells include Langerhans cells and intraepithelial lymphocytes in the cutaneous system, with organized collections like tonsils and Peyer patches in mucosal tissues.
Mucosal Immune System
- The mucosal immune system offers protection against microbial invasion, with mucus-secreting epithelium as a barrier.
- Specialized M cells transport antigens to underlying tissues; defenders include dendritic cells, T lymphocytes, and macrophages.
- Immunoglobulin A (IgA) is produced abundantly in mucosal tissues and neutralizes microbes.
Cellular Organization in Lymphoid Organs
- T and B lymphocytes are segregated in peripheral lymphoid organs.
- B cells are found in follicles at the cortex's periphery in lymph nodes, often featuring germinal centers after activation.
- T lymphocytes reside in the paracortex, adjacent to the B cell follicles.
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Description
Test your knowledge on the differences between adaptive and innate immunity, including lymphocytes, antigens, antibodies, and defense mechanisms. Explore the principal mechanisms of both types of immunity.
