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In this animation, we will
explain what antibodies are,
在这个动画中，我们将解释什么是抗体， 

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how they are made and how
they are most commonly used
它们是如何制作的以及它们最常用的方式

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in laboratory research.
在实验室研究。 

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Antibodies are proteins
that can specifically
抗体是特异性的蛋白质

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recognize foreign
invaders or pathogens,
认识外国入侵者或病原体， 

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such as viruses,
bacteria and parasites.
如病毒，细菌和寄生虫。 

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All pathogens express
a unique combination
所有病原体都表达出独特的组合

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of molecules, both inside and
outside their cell membranes.
细胞膜内外的分子。 

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These are called antigens.
这些被称为抗原。 

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Antibodies can
serve two functions.
抗体可以起到两种功能。 

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Antibodies can
neutralize pathogens
抗体可以中和病原体

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by binding to their antigens
and blocking their action,
通过与他们的抗原结合并阻止他们的行为， 

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such as preventing a
virus from entering a cell
例如防止病毒进入细胞

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or blocking a bacterial toxin.
或阻断细菌毒素。 

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Antibodies also mediate the
destruction of pathogens
抗体也介导病原体的破坏

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by acting as markers that other
cells in the immune system
通过充当免疫系统中其他细胞的标志物

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recognize.
认识。 

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Antibodies are produced
by specialized cells
抗体由特化细胞产生

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within the immune system called
B lymphocytes or B cells.
在免疫系统内称为B淋巴细胞或B细胞。 

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The immune system recognizes
a wide array of antigens
免疫系统识别多种抗原

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by producing millions of
different types of antibodies,
通过产生数百万种不同类型的抗体， 

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each recognizing a
different antigen,
每个识别不同的抗原， 

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with each B cell producing
only one particular antibody.
每个B细胞仅产生一种特定抗体。 

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Antibodies are Y-shaped
proteins and are made up
抗体是Y形蛋白质并且是组成的

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of four polypeptides
or protein chains:
四个多肽或蛋白质链： 

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two identical shorter
chains called light chains
两条相同的较短链称为轻链

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and two identical longer
chains called heavy chains.
和两条相同的长链称为重链。 

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The N-terminus of the
four polypeptide chains
四条多肽链的N-末端

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vary significantly in sequence
from one antibody to the next
从一种抗体到下一种抗体的序列显着不同

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and are called variable regions.
并称为可变区域。 

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Variable regions are
involved in antigen binding.
可变区参与抗原结合。 

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The other regions of
the polypeptide chains
多肽链的其他区域

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vary very little in sequence
among different antibodies
在不同抗体之间的序列变化非常小

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from the same species and
are called constant regions.
来自同一物种，被称为恒定区域。 

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The constant regions are
responsible for interacting
恒定区域负责交互

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with effector proteins that
mediate the immune response.
与效应蛋白质介导免疫反应。 

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Antibodies are
produced by B cells
抗体由B细胞产生

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through a process
of recombination
通过重组过程

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where the genes that code
for portions of the antibody
其中编码抗体部分的基因

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protein are
recombined or shuffled
蛋白质重组或改组

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to create many
different variations
创造许多不同的变化

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of the final protein.
最终的蛋白质。 

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Antibodies are first
expressed on the cell membrane
首先在细胞膜上表达抗体

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of immature or naïve B cells
that have not yet encoutered
尚未成熟的未成熟或幼稚B细胞

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antigens.
抗原。 

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Recognition of the
antigen by an antibody
通过抗体识别抗原

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leads to B cell
activation, which
导致B细胞活化，这

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results in its differentiation
and clonal expansion.
导致其分化和克隆扩展。 

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Differentiated B cells
or plasma cells in turn
依次分化的B细胞或浆细胞

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produce and secrete
large amounts
产生和分泌大量的

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of the respective
antibody, which
各自的抗体，哪个

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is released into
the blood stream
被释放到血液中

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to aid in the
finding and targeting
帮助发现和定位

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of additional pathogens
of the same type.
相同类型的其他病原体。 

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Upon antigen
binding, B cells can
抗原结合后，B细胞可以

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be induced to produce
additional antibody variation
被诱导产生额外的抗体变异

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through a process called
somatic hypermutation, where
通过一个称为体细胞超突变的过程，其中

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the DNA sequences that code for
the antibody's variable regions
编码抗体可变区的DNA序列

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can rapidly mutate.
可以迅速变异。 

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Antibodies with higher
affinity cause further B cell
具有更高亲和力的抗体引起进一步的B细胞

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activation, which results in
the selection and production
激活，这导致选择和生产

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of highly specific antibodies
to the antigen in question.
对所述抗原的高度特异性抗体

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Because of their
ability to bind proteins
因为它们能够结合蛋白质

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with exquisite
specificity, antibodies
具有精确的特异性，抗体

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are routinely used in research
to (1) quantify the relative
通常用于研究（1）量化相对

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amount of protein
present in a sample, (2)
样品中存在的蛋白质含量，（2） 

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to detect the addition of
a covalent modification
检测共价修饰的添加

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and the binding of other
proteins to the protein
以及其他蛋白质与蛋白质的结合

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of interest, (3) to
isolate a protein
感兴趣的，（3）分离蛋白质

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or protein complex
from a cell lysate,
或来自细胞裂解物的蛋白质复合物， 

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and (4) to visualize proteins,
cell structures and processes
 （4）使蛋白质，细胞结构和过程可视化

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under the microscope.
在显微镜下。 

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To produce antibodies against
an antigen of interest,
要产生针对目标抗原的抗体， 

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researchers inject the antigen
in question or a fragment of it
研究人员注射了有问题的抗原或其片段

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into a mammal such as a
rabbit, sheep or goat.
进入哺乳动物，如兔子，绵羊或山羊。 

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The resulting
antibodies are isolated.
分离所得抗体。 

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A polyclonal
antibody preparation
多克隆抗体制剂

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contains a mixture of
heterogeneous antibodies
含有异质抗体的混合物

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against multiple
sites of the antigen.
针对多个抗原位点。 

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A monoclonal
antibody preparation
单克隆抗体制剂

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contains an antibody
that recognizes only one
含有仅识别一种的抗体

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site on the antigen.
抗原上的位点。 

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Polyclonal and
monoclonal antibodies
多克隆和单克隆抗体

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have different strengths
and weaknesses.
有不同的优点和缺点。 

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Long-term production of
polyclonal antibodies
长期生产多克隆抗体

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requires the use of multiple
individual animals resulting
需要使用多个单独的动物

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in differences between
different batch preparations.
在不同的批次准备之间的差异。 

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In contrast, monoclonals
can be continuously produced
相反，可以连续生产单克隆抗体

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from a clonal cell
population, and are
来自克隆细胞群，并且是

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less subject to changes.
较少受到变化的影响。 

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Since polyclonals can
recognize multiple sites
由于polyclonals可以识别多个站点

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within a protein, they can
amplify detection signals,
在蛋白质中，它们可以放大检测信号， 

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but they also then
cross-react more
但他们也会交叉反应更多

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with non-specific proteins.
与非特异性蛋白质。 

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Monoclonals, on the
other hand, do not
另一方面，Monoclonals却没有

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amplify detection
signals as well
也放大检测信号

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but provide a lower
signal to noise ratio
但提供较低的信噪比

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due to their higher specificity.
由于它们的特异性较高。 

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As a result,
polyclonals are better
因此，多面体更好

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suited for detecting
proteins that
适合检测蛋白质

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are expressed at low levels.
以低水平表示。 

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They are also used
to effectively
它们也被用于有效

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detect different isoforms
or versions of a protein
检测不同的同种型或蛋白质的形式

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or to screen for the presence
of the protein of interest
或筛选感兴趣的蛋白质的存在

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in other species.
在其他物种。 

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Monoclonals are
more commonly used
单克隆抗体更常用

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when purifying a protein from
a mixture where specificity
从特异性混合物中纯化蛋白质时

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is important or when detection
of a very specific portion
很重要或当检测到非常特定的部分时

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of a protein or
modification is desired.
需要蛋白质或修饰物。 

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When detection or isolation
of a protein is desired,
当需要检测或分离蛋白质时， 

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researchers commonly use a
combination of two antibodies:
研究人员通常使用两种抗体的组合： 

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primary and
secondary antibodies.
一抗和二抗。 

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Primary antibodies bind
to specific antigens
一抗与特异性抗原结合

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while secondary antibodies
are made to recognize
而二抗则被识别

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and bind to the constant region
of primary antibodies, which
并与一抗的恒定区结合

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is the same within
a given species.
在给定的物种中是相同的。 

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Depending on the application,
secondary antibodies
根据应用，二抗

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might be conjugated to
marker or a bead, which
可以与标记物或珠子缀合，其中

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allows for easy
detection or isolation,
便于检测或隔离， 

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of the protein of interest.
感兴趣的蛋白质。 

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The use of a secondary
antibody leads
使用二抗导致

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to amplification in signal since
multiple secondary antibodies
由于多种二抗，因此可以扩增信号

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can bind to a primary antibody.
可以与一抗结合。 

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