Forum for Nordic Dermato-Venereology Nr2,2017 | Page 25

Hanna Brauner – Karolinska Dermatology Symposium, 2017 “The Microbiome in Health and Disease – Focus on SKIN”
gradual decrease in number of microbes in the lower parts of
the respiratory tract, possibly due to differential production
of antimicrobial peptides (Fig. 1).
Professor Normark also reviewed studies in which normal and
germ-free mice were fed with high fat diet and the normal
mice consequently became obese, but not the germ-free mice.
A fecal transfer from the obese mice to the germfree lean mice
however rendered them fat, pointing towards a role of the
commensals in obesity. In line with this, obese humans also
have an altered bacterial flora with much less of the bacteriodes
compared to firmicutes, and the bacterial ratio can be altered
upon dietary changes.
Skin microbiota in health and disease
Shruti Naik, Postdoctoral researcher, Rockefeller University, New York
effect of microbiome on peripheral immunity. In the gut it
was previously known that the balance between T effector cells
and T regulatory (T reg) cells was altered towards more T reg
cells in germ-free mice and normalized when commensals were
given to the mice. Dr Naik and colleagues infected germfree
mice with gut or skin tropic bacteria and found that gut tropic
bacteria specifically rescued the immune system in gut, and
skin tropic bacteria the immune system in skin through an
IL-1 dependent pathway.
Her work also revealed great differences in the immune mod-
ulatory impact by different strains and commensal specific
immune effects. For example, certain strains of S. epidermidis
uniquely causes induction of CD8b+ T cells. Such T cells are
interestingly found in psoriasis and squamous cell carcinoma
where they represent long lasting IL-17A+ CD8b T cells.
Commensal microbiota – a radical defender in times
of stress
Rolf Lood, Researcher, Lund University
Dr Lood discussed the intriguing concept of human-microbi-
ota symbiosis and put forward the hypothesis that this is not
merely achieved by the absence of virulence factors but also
the presence of unknown promoting factors.
Much of Dr Lood’s work and interest is centered around P.
acnes, which is found mainly in sebaceous glands. P. acnes
is associated to acne and in patients with psoriasis and AD a
reduction in P. acnes has been observed.
Dr Naik shifted the focus from gut to skin microbiome. We
learnt that skin microbiota represents the most diverse niche,
with around 1,000 species and 19 phyla, and that microor-
ganisms reside not only on the skin surface, but also in hair
follicles and in sebaceous glands. Perhaps this is the reason
for the skin microbiome being remarkably stable over time
and largely unaffected by external stress such as bathing and
application of skin creams. Skin resident microorganisms show
high tropism to certain habitats of our body, favoring either
for example dry or oily skin, and there is more intra-individual
than inter-individual diversity in the skin microbiome.
During her work as a graduate student in the Belkeid lab, Dr
Naik made major contributions to our understanding of the
Forum for Nord Derm Ven 2017, Vol. 22, No. 2
Dr Lood raised the question about the possible role of P. acnes
in these diseases. He identified a very conserved protein called
”RoxP” that is unique to P. acnes. One function of RoxP is to
bind heme, reduce free radicals and prevent damage caused
by oxidative stress. Several skin diseases are either initiated by
or progress through oxidative stress, caused by for example
UV radiation. Dr Lood thus speculates that P. acnes and RoxP
reduce the risk of developing certain skin diseases.
Anaerobic human intestinal microbiota and fecal
transplantation – clinical applications
Elisabeth Lissa Norin, Associate Professor, Karolinska Institutet,
Solna
Associate Professor Norin introduced and reviewed her inter-
esting work with the anaerobic cultivated human intestinal
microbiota (ACHIM), to use instead of fecal transplantation.
The ACHIM originates from fecal material and has been cul-
tivated for more than 20 years. Benefits of ACHIM over fecal
microbiota transplant (FMT) is that it is carefully monitored
M eeting R eport
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