The non-inflammatory defence is very important for the development of biofilm infections
in the lungs of patients with cystic fibrosis. In cystic fibrosis patients thick layers of
stiff dehydrated mucus compromise the mucociliary escalator system thereby disabling the ciliary
movement, which results in poor self-cleaning capacity to remove invading microorganisms
from the airways. And it is well accepted that this defective self-cleaning capacity
of the mucociliary escalator is the main reason for the higher susceptibility to biofilm infections
in the lungs of cystic fibrosis patients.
The immune response is the body’s response to antigens. Antigens include pathogen associated
molecular patterns such as extra-cellular DNA, various toxins, LPS and other microbial
components. Traditionally, the immune response has been
divided in the innate response and the adaptive response.
The innate immune response provides the fastest response, but it has only little specificity.
Approximately 300 receptors are involved in innate immunity. In principle the innate immune
system has no memory - the innate immune system will respond the same way if infectious microorganisms
infect the host several times. The humoral components of the innate immune system include
the complement system, cytokines and bactericidal peptides. The cellular component mainly consists
of polymorphonuclear leukocytes, also called the PMNs, the macrophages, Gamma Delta T cells
and epithelial cells.
The adaptive immunity provides a slower response that may take weeks to mature.
Contrary to the innate immune response the adaptive immune response has high specificity
and employs 1-10 million different receptors in the body. This allows the adaptive immune
system to develop ‘memory’ of infections –This ability to remember previous infections
is an integrated mechanism of all effective vaccines. The humoral components of adaptive
immune system involve antibodies and cytokines. Lymphocytes and dendritic cells dominate the
cellular components.
So which part of the immune system is activated against biofilm infections?
Some information may be obtained when considering the type of infection that predominates in
patients with primary immunodeficiencies. That is patients born with particular deficient
components of the immune response. We should also take into account that the infectious
biofilm is mainly caused by bacteria and by fungi.
If we take a closer look of this table, which shows the type of infection typically associated
with the major categories of primary immune deficiencies, we see that against bacterial
pathogens antibodies, phagocytes and the complement system are all important, but against mycobacteria
and fungi it appears that the phagocytes provide the most important part of the host defence.
In other words we could expect a response by the phagocytes against the biofilm formed
by both bacteria, mycobacteria and as well as by fungi. The phagocytes of the immune
response are dominated by PMNs and macrophages.
The third component of the host response to infection is the inflammatory response.
The inflammatory response is a reaction to tissue damage, and is not necessarily, as
with the activation of the immune system, caused by antigens.
Inflammation is characterized by pain, swelling, heat, redness and by loss of functionality.
The tissue damage leading to the inflammatory response may be caused by physical insults
such as pressure, temperature and radiation and by chemical insults such as acids, bases
Thomas BjarnsholtProfessor
