MadSci Network: Immunology |
Dear Bubbles,
There are a lot of key words in your sentence that have "specific"
meanings in immunology so your use of them might complicate my answer. Let
me start with a glossary.
There is something called NATURAL IMMUNITY which includes Natural
Antibodies and Natural Killer cells. This kind of immunity exists without
having to introduce an antigen or pathogen stimulus. The responses are
directed against common antigens that are found in a lot of organisms and
may even be found normally in the animal making the Natural Immunity.
Phosphoryl Choline is one of these antigens. It is found in bacterial cell
walls but it is also found in red blood cell membranes and other cell
membranes when they break down. Immunity to it may be part of the bodies
way of cleaning up rubbish left over from the wear and tear of life. The
antibodies also my slow down a pathogen briefly when it invades the
body.
Acquired Immunity is the kind of immunity you are asking about, I think.
This kind of immunity is always "specific", meaning it is directed only at
the particular virus or antigen that stimulated it and another different
virus introduced in such an immune individual will not be resisted.
The second part of your question involves a different kind of specificity.
I go to great length to explain this in my web site on Critical
Issues in Vaccine design. In brief, viruses (bacteria and parasites as
well) have ways of using some of the hosts own biology to find an
advantage after invading the body. These "tricks" involve use of molecules
that mimic normal molecules found in the animal this organism infects. The
effect of these molecules is to create "specificity" in the way the body
responds to each virus or other pathogen so that the kind of immunity may
be very different for one virus than it is for the other. Route of viral
invasion, kind of mimicked host protein, and ability to trigger the host
to up-regulate (induce to appear, increase amount or secrete) specific
hormones, proteins etc are ways a disease producing virus can alter how
our body responds to it. In some cases the virus induces the body to
respond with mostly an antibody response. This does the virus a favor
because it may be relatively resistant to antibody and killer T-cells are
needed to eradicate it. Catch-22, when antibody is emphasized killer T-
cells could be de-emphasized...giving the virus an advantage and vice
versa. In designing vaccines these tricks and the molecules used by the
virus to carry out the tricks need to be known so that the proper kind of
immunity develops.
Among tricks a virus uses to gain advantage include using some of the
molecules required by the host immune system for its function as targets
for its infection of the host. This is what the Human Immunodeficiency
Virus [HIV] does when it uses the CD-4 molecule and a chemokine receptor
to invade T-cells. The CD-4 molecule is on helper T-cells that are
important in regulating the initiation of immune responses. The CD-4
molecule is important in cell interactions needed for the function of
these cells. Chemokine receptors on T-cells have recently been found to be
a second molecule that the HIV virus uses to get into the cell. Chemokines are
important small molecules that control adhesion, migration and traffic of
lymphocytes from blood into lymphatic
tissues and places where immune responses take place.
So, Bubbles it seems that each virus is different and despite the
specificity of an immune response the virus itself has specific ways to
disrupt that specificity so that the kind of immunity to viruses is always
going to be different from that of another. Maybe this is why, after all
these years of making vaccine candidates by thousands of scientists we
only have a handful of safe and effective vaccines and luck was an
important part of those successes. In many serious situations luck is that
missing ingredient. We have to continue to toil at science in order to be
there with the right tool at the right time so luck has a chance.
Try the links in the MadSci Library for more information on Immunology.