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SOPHOMORE MEDICAL MICROBIOLOGY SECTION: IMMUNOLOGY OVERVIEW OF THE IMMUNE RESPONSE Lecturer: Louis B. Justement, Ph.D. 934-1429 lbjust@uab.edu Objectives: To review the functional relationships between the innate and acquired immune responses. This lecture will: 1) provide a more detailed description of the components of the innate immune response and their function; 2) describe the transition from the innate immune response to the adaptive immune response; and 3) provide contextual information regarding the anatomic regions of the body in which the innate and adaptive responses occur. Reading: Kuby Immunology – The topics covered are dealt with throughout the text. Thus, there is no specific reading assignment. THE INNATE IMMUNE RESPONSE The First Line of Defense The Innate immune system serves three important functions : 1) Innate immunity provides the first response to microbes thereby preventing infection and effectively eliminating the invading microbes in many instances. 2) The effector mechanisms of innate immunity are often used to eliminate microbes even during an adaptive immune response. 3) Innate immunity to microbes stimulates adaptive immune responses and can influence the nature of the adaptive immune response to make them optimally effective against different types of microbes. The Skin – Physical Barrier and Immune Organ: 1) Epithelial barriers – The epidermis comprises a physical barrier that microbes can not pass through. 2) Chemical barriers – Defensins are produced by neutrophils. These are small polypeptides that exhibit antibacterial activity. Additionally, the pH of the skin and oils or fatty acids produced by the epidermis and
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dermis, respectively, inhibit microbial growth. 3) Immunological barriers – Epidermis: Keratinocytes and melanocytes constitute the largest percentage of cells in the epidermis. Keratinocytes produce several cytokines that promote the innate immune response and mediate local inflammatory responses. The epidermis also contains Langerhan’s cells. - These constitute only 1% of epidermal cells but because of their long extensions they are able to cover 25% of the epidermal surface. - These cells are immature dendritic cells, which are able to ingest antigens and present them on their surface in the context of MHC class II. - Langerhan’s cells that pick up antigen will retract their extensions, leave the epidermis and migrate to the dermis. In the dermis they will home to lymphatic capillaries, enter the lymphatic system and travel to regional lymphnodes as veiled cells. In the lymphnode, they will act as antigen presenting cells (APC) to present antigens to T cells thereby initiating the adaptive immune response. Intraepidermal T lymphocytes
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