题目：下面的短文后有两项测试任务：(1)第23-26题要求从所给的6个选项中为第2-5段每段选择1个最佳标题;(2)第27-30题要求从所给的6个选项中为每个句子确定1个最佳选项。
The Processes of Immunity
1 Immunity can be defined as the power of an individual to resist or overcome the effects of a particular disease or some other harmful agent. Sometimes the words “immunity” and “resistance” are used interchangeably; but it is more accurate to think of immunity as a process which causes the effect of the invading bacteria to be unable to work before they have had a chance to set up an infection.
2 The chemical processes that produce immunity can be described briefly as follows. Every disease-producing bacterium that enters the body carries within itself a substance.
3 These antibodies destroy the poisonous substance of the disease-producing bacteria, or else act on them in a way that will make the bacteria more sensitive to the action of the white blood cells or other phagocytes. Antigens vary in their chemical structure and specific antigen will stimulate the body to produce only a specific antibody in response to it.
4 The antibody, then, will react only with the kind of antigen that caused its production and no other. This is the reason for the selective nature of immunity so that immunity to one disease does not necessarily cause a person to be immune to another. Indeed, it is possible to have immunity to one disease and sensitivity, its opposite, to a different disease. So it is useful to consider immunity as a selective process. This selective characteristic has a name; specificity.
5 There are two main groups of immunity: inherited immunity and acquired immunity. This second type may be acquired by natural or artificial means. In addition, an acquired immunity may be either active or passive.
graph 2 ________.
graph 3 ________.
graph 4 ________.
graph 5 ________.
Definition of Immunity
Process of Antibodies
Functions of Antibodies
Specific Character of Immunity
Types of Immunity
Functions of Immunity
bodies were produced when _____.
antibody will react only with _____.
main groups of immunity are _____.
ral or artificial means acquire _____.
rited immunity and acquired immunity
antigen is introduced into the body
ired immunity
ified immunity
gens vary in their chemical structure.
kind of antigen that caused its production and no other
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