Biology Reference
In-Depth Information
VACCINATION
Our ability to produce millions or billions of different antibodies was used
to develop the most powerful tool to prevent infectious diseases, namely
vaccination. Jenner was credited for the discovery of vaccination (Osler,
1918), although it was actually employed by a Dorsetshire farmer to protect
his family from small pox infection with cow pox (vaccinia). The idea is
that some protein or other substances on less virulent or attenuated bacterial
or viral agents can stimulate our immune system to produce specific
antibodies against them. Subsequent infections of similar or pathogenic
bacteria or viruses can result in the binding of our antibodies specifically to
these bacteria or viruses to promote their being engulfed by macrophages,
leukocytes, etc. For each antigen, the production of specific antibodies is on
random basis. Some of the antibodies would have high binding affinities,
while others not so high. Furthermore, the duration of production of these
antibodies varies. Thus, the standard practice is that periodically, booster
vaccination will be required.
On the other hand, some infectious agents, e.g. the flu virus, the human
immunodeficiency virus (HIV), etc., can mutate their surface protein
molecules thus avoiding their binding to our antibodies. It is for this reason
that flu vaccination is required yearly for different strains of viruses. An
effective vaccine for HIV is still under development. Recently, DNA
segments coding for some of the surface proteins of HIV have been used for
vaccination. Hopefully, these segments can be incorporated into our
chromosomes and direct the synthesis of specific viral proteins on
continuous basis. In particular, these segments have been used to replace
the CDRH3 of human antibody genes, so that such pieces of viral proteins
are indeed presented on the surface of a protein in a loop configuration.
Another method of preventing bacterial or viral infection is passive
immunity. Antibodies from a donor, usually in the form of serum gamma
globulin, can be injected into recipients for temporary protection. This is
sometimes used for travelers to some countries with a number of prevalent
infectious diseases. Serum gamma globulin probably contains millions of
different antibodies, a few of which may be particularly useful to combat
these infectious diseases.
The above mentioned techniques have lately been extended to the treatment
of cancer. The idea is that to a certain extent cancer cells are foreign.
Presumably, some of their cell surface molecules are different from those on
normal cells or are extra abundant. Thus, specific antibodies may be raised
