Biomedical Engineering Reference
In-Depth Information
Although it is important to stress that the immune system
comprises a highly integrated set of molecular and cellular
mechanisms, in the past couple of decades researchers have found
it useful to group these mechanisms into “adaptive” and “innate”
immunity, respectively.
Adaptive immunity (often also referred to as acquired immunity)
comprises complex cellular mechanisms that permit a highly
diversified immune response to microbial or other stimulating
challenges and includes a recall response upon repeated exposure.
Adaptive immunity has been the focus of intense research, mainly
because this part of the immune system in consequence of the recall
response can be manipulated by vaccination. Injection of microbial
proteins or carbohydrates, in the context of vaccination referred to
as the antigen, will stimulate an immune response that may protect
vaccinated individuals against future infection with viruses. We now
have a detailed picture of the processes delivering this protection,
which mainly depend on the formation of so-called antibodies.
As discussed below, a similar response may also be encountered
following the introduction of nanomaterials in the body.
Innate immunity comprises cellular and molecular mechanisms
that act as a first line of defense against infection. Proteins of the
innate immune system take a structure that permits efficient binding
to potential microbial pathogens. The binding of these molecules
to microbial surfaces initiates a number of immunological eff ector
mechanisms involving leukocytes as well as plasma proteins, which
leads to the elimination of the microbe. Unlike adaptive immunity,
the functional properties of innate immunity are largely unaltered
throughout life and comprise no known mechanisms that would
permit a recall response. With the similarity between certain
microbial molecules and those utilized for the manufacture of
nanomaterials, innate immunity plays a major role in the immune
response evoked by these materials.
10.2.1
Antigen Recognition by Antibodies
Antibodies belong to immunoglobulin (Ig) superfamily of proteins
and are exclusively synthesized by B cells in the lymph nodes or
by plasma cells, a more diff erentiated state of B cells, which is able
to produce approximately 3200 secreted Ig molecules per cell per
second [3]. The ability of B cells to bind antigens is regulated by
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