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Questions and Answers
What is the primary function of the epithelial barriers of the skin?
What is the primary function of the epithelial barriers of the skin?
What is the estimated number of immune cells per square centimeter of human skin?
What is the estimated number of immune cells per square centimeter of human skin?
What is the primary role of keratin on the surface of the skin?
What is the primary role of keratin on the surface of the skin?
What type of lymphocytes are found in the epithelia of the skin?
What type of lymphocytes are found in the epithelia of the skin?
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What is the pH of the skin due to the production of sebum?
What is the pH of the skin due to the production of sebum?
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What do epithelial cells produce to kill bacteria and some viruses?
What do epithelial cells produce to kill bacteria and some viruses?
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What is the primary route of acquisition for most microbial infections?
What is the primary route of acquisition for most microbial infections?
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What is the outer layer of the skin called?
What is the outer layer of the skin called?
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What is the primary function of keratinocytes in the skin?
What is the primary function of keratinocytes in the skin?
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What is the primary function of Pattern Recognition Receptors (PRRs)?
What is the primary function of Pattern Recognition Receptors (PRRs)?
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What is the role of Birbeck granules in Langerhans cells?
What is the role of Birbeck granules in Langerhans cells?
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What is the result of the complement cascade?
What is the result of the complement cascade?
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What is the role of Langerhans cells in the skin?
What is the role of Langerhans cells in the skin?
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What is the result of the migration of Langerhans cells to the lymph nodes?
What is the result of the migration of Langerhans cells to the lymph nodes?
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What is the function of Toll-like Receptors (TLRs)?
What is the function of Toll-like Receptors (TLRs)?
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What is the role of fibroblasts in the dermis?
What is the role of fibroblasts in the dermis?
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What is the primary function of Langerhans cells in the skin?
What is the primary function of Langerhans cells in the skin?
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What is the skin-homing marker characterized by T cells in the skin?
What is the skin-homing marker characterized by T cells in the skin?
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What is the primary function of the inflammatory response?
What is the primary function of the inflammatory response?
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What is the role of neutrophils in the inflammatory response?
What is the role of neutrophils in the inflammatory response?
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What is the effect of bacterial LPS on Langerhans cells?
What is the effect of bacterial LPS on Langerhans cells?
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What is the role of macrophages in the inflammatory response?
What is the role of macrophages in the inflammatory response?
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What is the function of E-selectin/ELAM-1?
What is the function of E-selectin/ELAM-1?
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What is the role of CD4 T cells in the immune response to infection?
What is the role of CD4 T cells in the immune response to infection?
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Study Notes
The Cutaneous Immune System
- The skin is the largest organ of the body, with up to 10^6 immune cells/cm^2.
- It provides the first line of defense against microorganisms through epithelial barriers.
- The skin consists of both innate and adaptive immunity cells.
Epithelial Barriers
- Keratin on the skin's surface prevents most microbes from interacting with and infecting the epithelia.
- Epithelial cells produce antimicrobial peptides, including defensins and cathelicidins, which kill bacteria and some viruses.
- Epithelia contain lymphocytes called intraepithelial T lymphocytes that recognize microbial lipids and react against infectious agents.
Innate Immune Components in Skin
- Most microbial infections are acquired through the epithelial barrier of the skin, gastrointestinal, respiratory, and genitourinary systems.
- Epithelial cells provide physical barriers and antimicrobial molecules.
- Lymphoid cells are also present in the skin.
Pattern Recognition Receptors (PRRs)
- Toll-like Receptors (TLRs) are specific for microbial structures.
Review: Complement
- The complement cascade amplifies the reaction, leading to the generation of a rigid protein-lined transmembrane channel, the membrane attack complex (MAC).
Immune Players in the Skin
- Keratinocytes express high levels of IL-1, which promotes inflammation and repair when the skin is damaged.
- Fibroblasts in the dermis respond to TNFα by releasing IL-15, which activates effector T cells.
Langerhans Cells
- Langerhans cells are a type of immature conventional dendritic cells that reside in the skin.
- They are rich in MHC class II molecules and carry processed antigens.
- They are actively phagocytic and contain large granules known as Birbeck granules.
- They migrate to the lymph nodes, carrying antigens from the skin to the T helper cells.
T Cells in the Skin
- T cells are present in normal skin and immune responses are characterized by T cell infiltration.
- T cells constitute the major cell type present in both normal skin and immune reactions.
- They are characterized by a skin-homing marker CLA (cutaneous lymphocyte antigen) and the chemokine receptors.
Inflammation
- Inflammation is the response of tissue to injury, bringing serum molecules and cells of the immune system to the site of damage.
- Three components of the inflammatory response:
- Increased blood supply to the region.
- Increased capillary permeability.
- Emigration of leukocytes from blood vessels into the tissues.
Immune Reaction to Infection
- Langerhans cells ingest microbes and are activated by bacterial LPS through the TLR signaling pathway.
- Bacterial LPS induces two changes in Langerhans cells:
- Stimulating them to migrate and enter the lymphatic system.
- Initiating adaptive immunity by activating CD4 T cells.
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Description
Learn about the skin's role in providing the first line of defense against microorganisms, including its epithelial barriers and immune cells. Discover how keratin and antimicrobial peptides help prevent infections.
