MadSci Network: Immunology
Query:

Re: How does the immune system recognize the rubeola virus when vacinated?

Date: Thu May 14 03:29:50 2009
Posted By: Djordje Miljkovic, Post-doc/Fellow, Imunology, Institute for Biological Research
Area of science: Immunology
ID: 1236099829.Im
Message:

There is a nice article about vaccination at Wikipedia
(http://en.wikipedia.org/wiki/Vaccine). There you can find that: "A vaccine
is a biological preparation that establishes or improves immunity to a
particular disease. A vaccine typically contains a small amount of an agent
that resembles a virus or other microorganism. The agent stimulates the
body's immune system to recognize the agent as foreign, destroy it, and
"remember" it, so that the immune system can more easily recognize and
destroy any of these microorganisms that it later encounters."
Also, there is written that: "Vaccines are dead or inactivated organisms or
purified products derived from them. There are several types of vaccines
currently in use. These represent different strategies used to try to
reduce risk of illness, while retaining the ability to induce a beneficial
immune response."
Thus if you think about making vaccine against some virus you are supposed
to preserve its antigenic properties and to avoid its virulent
(disease-provoking, killer, destructive) properties. To this end, you can
kill the virus, or genetically modify it so that it is not virulent any
more, or make recombinant antigens of the virus, or perform some other
manipulation.
Regarding immune system, successful vaccination procedure means that the
elements of the immune system recognize the virus, react to it by means of
adaptive immune response and produce a long-term memory that protects
against real infection by the same virus. For this it is not important to
have intact virus or all the components of the virus. This fact is used to
make vaccines that contain the parts of the virus that are to be recognized
by immune system, and that do not contain the dangerous disease-provoking
parts of the same virus. Efficiency of the protection is mostly about
immunological memory. If you understand how the immunological memory works,
you will understand how vaccination works. Now, our comprehension of
immunological memory is far from complete, and there are still things to be
resolved. However, in many textbooks of immunology you can find current
opinion about immunological memory and vaccination. For the beginning,
Wikipedia can help you as well
(http://en.wikipedia.org/wiki/Immunological_memory).
And for the direct answer to your question. Antigen presenting cell will
have to eat virus or its parts present in vaccine, they will have to
process it and to present virus-specific antigens to T helper (Th) cells
which will then help antigen-specific B cells that have already recognized
virus-specific antigens to produce antibodies and to differentiate into
memory B cells. Viral particles or parts that were present in the vaccine
will be eliminated from the body and memory Th and B cells will stay for a
long period, ready to react fast and strongly against possible infection by
the same virus. A small problem is that a virus is intracellular pathogen
and it would be very nice if vaccination would also provoke cytotoxic T
cell (Tc) response, as this would make also Tc memory cells ready to
respond to the intracellular infection. However, this is not so easy to
achieve, as modification of virus in order to make it non-virulent usually
interferes with its capability to infect cells. Some vaccines containing
attenuated virus particles accomplish both B and Tc response. Whatsoever,
if vaccine is provoking just the B cell memory, it is still protective, as
antibodies produced by B cells prevent infection of cells by the virus. You
can find additional data about the topic in regular textbook of Immunology
(Cellular and Molecular Immunology, by Abul K. Abbas, MBBS, Andrew H.
Lichtman, MD, PhD and Shiv Pillai, MD)






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