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Polyclonal B cell response is a natural mode of immune response exhibited by the adaptive immune system of mammals. It ensures that a single antigen is recognized and attacked through its overlapping parts, called epitopes, by multiple clones of B cell. In the course of normal immune response, parts of pathogens (e.g. bacteria) are recognized by the immune system as foreign (non-self), and eliminated or effectively neutralized to reduce their potential damage. Such a recognizable substance is called an antigen. The immune system may respond in multiple ways to an antigen; a key feature of this response is the production of antibodies by B cells (or B lymphocytes) involving an arm of the immune system known as humoral immunity. The antibodies are soluble and do not require direct cell-to-cell contact between the pathogen and the B-cell to function. Antigens can be large and complex substances, and any single antibody can only bind to a small, specific area on the antigen. Consequently, an effective immune response often involves the production of many different antibodies by many different B cells against the ''same'' antigen. Hence the term "polyclonal", which derives from the words ''poly'', meaning ''many'', and ''clones'' ("Klon"=Greek for sprout or twig);〔〔(【引用サイトリンク】Etymology of "clone" )〕 a clone is a group of cells arising from a common "mother" cell. The antibodies thus produced in a polyclonal response are known as polyclonal antibodies. The heterogeneous polyclonal antibodies are distinct from monoclonal antibody molecules, which are identical and react against a single epitope only, i.e., are more specific. Although the polyclonal response confers advantages on the immune system, in particular, greater probability of reacting against pathogens, it also increases chances of developing certain autoimmune diseases resulting from the reaction of the immune system against native molecules produced within the host. == Humoral response to infection == Diseases which can be transmitted from one organism to another are known as infectious diseases, and the causative biological agent involved is known as a pathogen. The process by which the pathogen is introduced into the body is known as inoculation,〔The term ''"inoculation"'' is usually used in context of active immunization, i.e., deliberately introducing the antigenic substance into the host's body. But in many discussions of infectious diseases, it is not uncommon to use the term to imply a spontaneous (that is, without human intervention) event resulting in introduction of the causative organism into the body, say ingesting water contaminated with Salmonella typhi—the causative organism for typhoid fever. In such cases the causative organism itself is known as the ''inoculum'', and the number of organisms introduced as the "dose of inoculum".〕〔(【引用サイトリンク】title= Definition of ''inoculation'' )〕 and the organism it affects is known as a biological host. When the pathogen establishes itself in a step known as colonization,〔 〕 it can result in an infection,〔 consequently harming the host directly or through the harmful substances called toxins it can produce.〔 This results in the various symptoms and signs characteristic of an infectious disease like pneumonia or diphtheria. Countering the various infectious diseases is very important for the survival of the susceptible organism, in particular, and the species, in general. This is achieved by the host by eliminating the pathogen and its toxins or rendering them nonfunctional. The collection of various cells, tissues and organs that specializes in protecting the body against infections is known as the immune system. The immune system accomplishes this through direct contact of certain white blood cells with the invading pathogen involving an arm of the immune system known as the cell-mediated immunity, or by producing substances that move to sites ''distant'' from where they are produced, "seek" the disease-causing cells and toxins by specifically〔''Specificity'' implies that two different pathogens will be actually viewed as two distinct entities, and countered by different antibody molecules.〕 binding with them, and neutralize them in the process–known as the humoral arm of the immune system. Such substances are known as soluble antibodies and perform important functions in countering infections.〔Actions of antibodies: * Coating the pathogen, preventing it from adhering to the host cell, and thus preventing colonization * Precipitating (making the particles "sink" by attaching to them) the soluble antigens and promoting their clearance by other cells of immune system from the various tissues and blood * Coating the microorganisms to attract cells that can engulf the pathogen. This is known as opsonization. Thus the antibody acts as an ''opsonin''. The process of engulfing is known as phagocytosis (literally, ''cell eating'') * Activating the complement system, which most importantly pokes holes into the pathogen's outer covering (its cell membrane), killing it in the process * Marking up host cells infected by viruses for destruction in a process known as Antibody-dependent cell-mediated cytotoxicity (ADCC)〕 Image:Neutrophil.png|Neutrophil Image:Eosinophil2.png|Eosinophil Image:Basophil.png|Basophil Image:Lymphocyte.png|Lymphocyte Image:Monocyte.png|Monocyte Image:Macrophage.png|Macrophage 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Polyclonal B cell response」の詳細全文を読む スポンサード リンク
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