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  • Don’t get into the minor details of the passage; just focus on what each paragraph has to say
  • As you read, create a map of the passage; you must remember what thing is located where in the passage
  • Once you read the question, come back to the part of the passage that is likely to have the answer
  • Compare the options and eliminate the incorrect choices based on the evidence that you see in the passage
  • Choose the answer once you are convinced of the right choice

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Reading Comprehension Practice Passage

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 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.


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Question: The author is primarily concerned with

proving that immunological reactions do not involve antibodies
establishing that most immunological reactions involve antigens
criticizing scientists who will not change their theories regarding immunology
analyzing the importance of cells in fighting disease
explaining two different kinds of immunological reactions

Question: The author argues that the antigen-antibody explanation of immunity “had to seriously qualified” because

antibodies were found to activate unstable components in the blood
antigens are not exactly complementary to antibodies
lymphocytes have the ability to bind to the surface of antigens
antibodies are synthesized from protein whereas antigens are made from nucleic acid
antigens have no apparent mechanism to direct the formation of an antibody

Question: The author most probably believes that the antigen-antibody theory of immunological reaction.

is wrong
was accepted without evidence
is unverifiable
is a partial explanation
has been a divisive issue among scientists

Question: The author mentions all of the following as being involved in antigen-antibody immunological reactions EXCEPT the

synthesis of a protein
activation of complement in the bloodstream
destruction of antibodies
entrapment of antigens by macrophages
formation of a substance with a structure complementary to that of an antigen

Question: The passage contains information that would answer which of the following questions about cell-mediated immunological reactions?

I. Do lymphocytes form antibodies during cell-mediated immunological reactions?
II. Why are lymphocytes more hostile to antigens during cell-mediated immunological reactions than are other cell groups?
III. Are cell-mediated reactions more pronounced after transplants than they are after parasites have invaded the organism?
I only
I and II only

Question: The passage suggests that scientists might not have developed the theory of cell-mediated immunological reactions if

proteins existed in specific group types
proteins could have been shown to direct the synthesis of other proteins
antigens were always destroyed by proteins
antibodies were composed only of protein
antibodies were the body’s primary means of resisting disease

Question: According to the passage, antibody-antigen and cell-mediated immunological reactions both involve which of the following processes?

I. The destruction of antigens
II. The creation of antibodies
III. The destruction of intracellular parasites
I only
II only

Question: The author supports the theory of cell-mediated reactions primarily by

pointing out a contradiction in the assumption leading to the antigen-antibody theory
explaining how cell mediation accounts for phenomena that the antigen-antibody theory cannot account for
revealing new data that scientists arguing for the antigen-antibody theory have continued to ignore
showing that the antigen-antibody theory fails to account for the breakup of antigens
demonstrating that cell mediation explains lysis and phagocytosis more fully than the antigen-antibody theory does

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