ANTIBODY-BASED TECHNIQUES - A Guide to Methods in the Biomedical Sciences - page 69

Chapter 4

ANTIBODY-BASED TECHNIQUES

A. Introduction

Antibodies are a group of serum glycoproteins of related structure that
help protect us against invading pathogens. Antibodies are highly spe-
cific for the immunogen, and generally bind with high affinity to antigenic
determinants, known as epitopes, on the immunogen. Antibodies that
have been produced against an immunogen can be purified from serum
using, for example, affinity chromatography. These purified antibodies
are generally heterogeneous in that they recognize different epitopes
on the immunogen and bind with different affinities. These serum an-
tibodies are referred to as polyclonal antibodies since they have been
produced by many different clones of antibody secreting cells. Antibody
secreting cells, also referred to as plasma cells, differentiate from B lym-
phocytes in response to foreign antigens. Antibodies are crucial to the
clearance of many pathogens like viruses and bacteria from our bodies.
The most remarkable feature of antibodies is their ability to be produced
against almost any type of macromolecule, especially proteins and car-
bohydrates, whether these are naturally occurring or synthesized de
novo in the laboratory.
Major discoveries on the role of antibodies in adaptive immune re-
sponses have been met with a number of Nobel prizes to investiga-
tors during the century (see Table 3). However, antibodies have
also become one of the most important tools in biomedical research
because of their ease of production and characteristic specificity and
affinity.
There are a number of different isotypes (also called classes) of anti-
bodies that have distinct biologic activities. In most mammals there are
5 isotypes, IgM, IgG, IgA, IgE, and IgA. The biologic activities of these
antibody classes are quite varied. While some pathogens, especially
viruses, may be inactivated by antibody binding, most are not destroyed