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The antigen-antibody immunological reaction used to be

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The antigen-antibody immunological reaction used to be [#permalink] New post 17 May 2010, 10:01
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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
[Reveal] Spoiler:

2. The author argues that the antigen-antibody explanation of immunity “had to seriously qualified” (line 37) because
(A) antibodies were found to activate unstable components in the blood
(B) antigens are not exactly complementary to antibodies
(C) lymphocytes have the ability to bind to the surface of antigens
(D) antibodies are synthesized from protein whereas antigens are made from nucleic acid
(E) antigens have no apparent mechanism to direct the formation of an antibody
[Reveal] Spoiler:

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
[Reveal] Spoiler:

4. The author mentions all of the following as being involved in antigen-antibody immunological reactions EXCEPT the
(A) synthesis of a protein
(B) activation of complement in the bloodstream
(C) destruction of antibodies
(D) entrapment of antigens by macrophages
(E) formation of a substance with a structure complementary to that of an antigen
[Reveal] Spoiler:

5. 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?
(A) I only
(B) I and II only
(C) I and III only
(D) II and III only
(E) I, II, and III
[Reveal] Spoiler:

6. The passage suggests that scientists might not have developed the theory of cell-mediated immunological reactions if
(A) proteins existed in specific group types
(B) proteins could have been shown to direct the synthesis of other proteins
(C) antigens were always destroyed by proteins
(D) antibodies were composed only of protein
(E) antibodies were the body’s primary means of resisting disease
[Reveal] Spoiler:

7. 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
(A) I only
(B) II only
(C) III only
(D) I and II only
(E) II and III only
[Reveal] Spoiler:

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
(E) demonstrating that cell mediation explains lysis and phagocytosis more fully than the antigen-antibody theory does
[Reveal] Spoiler:

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Re: Tough passage!!!! [#permalink] New post 07 Jun 2010, 07:32
gmatprep09 wrote:

What do you guys think of this passage. I found this pretty confusing. Is there a strategy to tackle these kind of passages and questions? If possible, can you include your reasoning for each question? Thanks

[Reveal] Spoiler:
1. E; 2. E; 3. D; 4. C; 5. A; 6. B; 7. A; 8. B.

m answers
1 E 04:36 correct
2 E 02:56 correct
3 B 01:14 incorrect
4 A 00:27 incorrect
5 A 00:17 correct
6 d 02:57 incorrect
7 e 00:30 incorrect
8 D 04:18 incorrect :)

what a heartbreaker it is ....
on a serious note if i look back the passage and read the answer options again , I could have got 4 , 7,8 correct ..need to learn to stay focussed in passages like these...but a toughie..i it comes in exam it will take away lot of time ....for sure..
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Re: Tough passage!!!! [#permalink] New post 03 Jul 2010, 02:12
Good passage, dont want such to appear on an exam day.
By the way, what is the source of such a passage?
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Re: Tough passage!!!! [#permalink] New post 09 Jul 2010, 22:50
1. E; 2. E; 3. A; 4. B; 5. A; 6. B; 7. A; 8. B.

Tough one ... Got 2 wrong .... :(
I did the whole passage in close to 12 mins .. I need to scale up my reading speed
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Re: Tough passage!!!! [#permalink] New post 30 May 2011, 19:49
Got 2 wrong in 10 minutes ..... & when i looked back at choices .... they would have been correct if given more time to passage. :oops:
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Re: Tough passage!!!! [#permalink] New post 30 May 2011, 21:35
3 wrong in approx 15 mins..
i would be doomed in exam....

Guys, any idea what should be the ideal time dedicated to this kind of passgae with 8 questions?


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Re: Tough passage!!!! [#permalink] New post 31 May 2011, 06:32
From what I have heard the GMAT RC passage does not involve more than 3 to 5 questions max per passage.


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Re: Tough passage!!!! [#permalink] New post 02 Jun 2011, 23:00
Good passage
3 incorrect , 15 minutes; Clearly this area needs improvement
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Re: Tough passage!!!! [#permalink] New post 03 Jun 2011, 02:34
got 7 out of 8 right , but the timing was 14:44 mins , this was not difficult but i had no paper and pen.
i went for B in question no.5 and that question took time because it was an except question , wasted almost 1:30 mim in q.5 and got it wrong.

can anyone clarify why the answer is A and not B in q 5 ?


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Re: Tough passage!!!! [#permalink] New post 16 Jul 2011, 20:41
Could somebody explain me why is the answer to Question 1 " author's primary concern" is E and not D?
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Re: Tough passage!!!! [#permalink] New post 22 Aug 2011, 01:45
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Re: The antigen-antibody immunological reaction used to be [#permalink] New post 08 Jan 2012, 22:31
Got 5 correct in 9:30 mins.Very tough!
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Re: The antigen-antibody immunological reaction used to be [#permalink] New post 27 Mar 2012, 17:12
Last question incorrect around 14 minutes


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Re: The antigen-antibody immunological reaction used to be [#permalink] New post 28 Mar 2012, 22:00
16 mins

5 right.
It was tough I would say
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Re: The antigen-antibody immunological reaction used to be [#permalink] New post 04 Jun 2012, 00:19
This paragraph is quite confusing. It took me 13 mins and I still got 4 wrong. Definitely 700 level.
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Re: The antigen-antibody immunological reaction used to be [#permalink] New post 07 Mar 2014, 03:33
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Re: The antigen-antibody immunological reaction used to be   [#permalink] 07 Mar 2014, 03:33
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