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The antigen-antibody immunological reaction used to be regarded as typical of immunological responses. Antibodies are proteins synthesized by specialized cells called plasma cells, which are formed by lymphocytes (cells from the lymph system) when an antigen, a substance foreign to the organism’s body, comes in contact with lymphocytes. Two important manifestations of antigen-antibody immunity are lysis, the rapid physical rupture of antigenic cells and the liberation of their contents into the surrounding medium, and phagocytosis, a process in which antigenic particles are engulfed by and very often digested by macrophages and polymorphs. The process of lysis is executed by a complex and unstable blood constituent known as complement, which will not work unless it is activated by a specific antibody; the process of phagocytosis is greatly facilitated when the particles to be engulfed are coated by a specific antibody directed against them. The reluctance to—abandon this hypothesis, however well it explains specific processes, impeded new research, and for many years antigens and antibodies dominated the thoughts of immunologists so completely that those immunologists overlooked certain difficulties. Perhaps the primary difficulty with the antigen-antibody explanation is the informational problem of how an antigen is recognized and how a structure exactly complementary to it is then synthesized. When molecular biologists discovered, moreover, that such information cannot flow from protein to protein, but only from nucleic acid to protein, the theory that an antigen itself provided the mold that directed the synthesis of an antibody had to be seriously qualified. The attempts at qualification and the information provided by research in molecular biology led scientists to realize that a second immunological reaction is mediated through the lymphocytes that are hostile to and bring about the destruction of the antigen. This type of immunological response is called cell-mediated immunity. Recent research in cell-mediated immunity has been concerned not only with the development of new and better vaccines, but also with the problem of transplanting tissues and organs from one organism to another, for although circulating antibodies play a part in the rejection of transplanted tissues, the primary role is played by cell-mediated reactions. During cell-mediated responses, receptor sites on specific lymphocytes and surface antigens on the foreign tissue cells form a complex that binds the lymphocytes to the tissue. Such lymphocytes do not give rise to antibody-producing plasma cells but themselves bring about the death of the foreign-tissue cells, probably by secreting a variety of substances, some of which are toxic to the tissue cells and some of which stimulate increased phagocytic activity by white blood cells of the macrophage type. Cell-mediated immunity also accounts for the destruction of intracellular parasites. 1. The author is primarily concerned with (A) proving that immunological reactions do not involve antibodies (B) establishing that most immunological reactions involve antigens (C) criticizing scientists who will not change their theories regarding immunology (D) analyzing the importance of cells in fighting disease (E) explaining two different kinds of immunological reactions
AN: E 請問這篇不是後面的理論推翻前面嗎(The antigen-antibody immunological reaction used to be regarded as typical of immunological responses.) 3. The author most probably believes that the antigen-antibody theory of immunological reaction. (A) is wrong (B) was accepted without evidence (C) is unverifiable (D) is a partial explanation (E) has been a divisive issue among scientists AN: D 這題在文中的定位在哪啊 8. The author supports the theory of cell-mediated reactions primarily by (A) pointing out a contradiction in the assumption leading to the antigen-antibody theory (B) explaining how cell mediation accounts for phenomena that the antigen-antibody theory cannot account for (C) revealing new data that scientists arguing for the antigen-antibody theory have continued to ignore (D) showing that the antigen-antibody theory fails to account for the breakup of antigens（B） (E) demonstrating that cell mediation explains lysis and phagocytosis more fully than the antigen-antibody theory does AN:B 小弟選a文中第二段不是推翻一個原本的理論而使antigen-antibody immunological reaction的理論受到質疑嗎 希望各位高手能幫我解答3q
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