Immunology-part2-four

Immunology-part2-four - 18 Four characteristics of the...

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The Innate (non-specific) Immune System The Adaptive (specific) Immune System 18 Four characteristics of the Adaptive immune system Four characteristics of the immune system: ! 1. Specificity (reaction to specific antigens) : " Antigens are organisms or molecules that are specifically recognized by T cell receptors and antibodies. " The sites on antigens that the immune system recognizes are the antigenic determinants (or epitopes ). " Each antigen typically has several different antigenic determinants. " The host creates T cells and/or antibodies that are specific to the antigenic determinants. Figure 18.6 Each Antibody Matches an Antigenic Determinant 18 ! 2. Diversity: " It is estimated that the human immune system can distinguish and respond to 10 million different antigenic determinants. ! 3. Distinguishing self from nonself: " Each normal cell in the body bears a tremendous number of antigenic determinants. It is crucial that the immune system leaves these alone. ! 4. Immunological memory: " Once exposed to a pathogen, the immune system remembers it and mounts future responses much more rapidly. Four characteristics of the Adaptive immune system
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18 • The adaptive immune system has two responses against invaders: The humoral immune response The cellular immune response • The two responses operate in concert and share mechanisms. The Adaptive Immune System 18 Humoral immune response • The humoral immune response is based on B cells . • B cells produce specific antibodies that recognize antigenic determinants by shape and composition. • Antibodies recognize pathogens in extracellular spaces (blood, lymph, exocrine secretions). “humor” (Latin for “fluid”) 18 • The cellular immune response is able to detect antigens that reside within body cells . • It destroys virus-infected or mutated cells. • Its main component consists of T cells . • T cells have T cell receptors that can recognize and bind specific antigenic determinants. Cellular immune response 18 Fundamental questions There are millions of B- and T-cells that each make different antibodies and T-cell receptors, respectively. ! How does the enormous diversity of B cells and T cells arise? ! How are B and T cells selected to mount an immune response? ! Why don’t antibodies and T cells attack and destroy our own bodies? ! How can the memory of postexposure be explained?
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The answer: clonal selection Clonal Selection of B Cells Millions of B cells expanded clone of identical B cells proliferation differentiation into “plasma cells” that secrete antibody differentiation into “memory cells” 18 Effector cells and memory cells • An activated lymphocyte (B cell or T cell) produces two types of daughter cells: effector and memory cells. Effector B cells
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This note was uploaded on 03/01/2009 for the course MCDB 1B taught by Professor Weimbs during the Spring '08 term at UCSB.

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Immunology-part2-four - 18 Four characteristics of the...

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