Biography
Biography: Audrey GUENICHE
Abstract
Probiotics have immunomodulatory functions through their activities on immunocompetent cells. Previously it was demonstrated
that supplementation with Lactobacillus johnsonii (La1) reinforces in human skin immune homeostasis and prevents UVmediated
immune-suppression, by promoting a faster recovery of Langerhans cells’ (LC) functions and basal CD1a+ cells number.
A new randomized, double-blind, placebo-controlled clinical trial was conducted with 54 healthy volunteers receiving either La1 (109
CFU/day) or placebo, during 57 days prior to UV (2 x 1.5 MED). Blister roofs, liquid and skin biopsies were collected 1, 4 and 10 days
aft er UV exposure from non-irradiated and irradiated skin areas and used for identifi cation of cells involved in UV-induced immune
response and quantifi cation of infl ammatory cytokines. While a similar decrease of LC for both groups was observed on day 1 aft er UV
exposure compared to placebo, La-1 group presented an increase of a new subset of epidermal dendritic cells (DC), namely early LC
precursors (CD1alow CD207-) associated with a minor recruitment of monocytes. Concomitantly, inhibition of IL-10 stimulation and
a tendency to inhibit IL-6 production was observed in La-1 group compared to placebo. On day 4, La-1 group presented signifi cantly
more early LC precursors and a trend to increase CD1alow CD207+ LC late precursors compared to placebo. Additionally, a faster
reduction of infl ammatory cytokines (IL-6, TNFalpha, IL-8, and IL-10) was observed in La1 group compared to placebo. Finally, 10
days aft er the UV challenge, even a similar recovery of the LCs was observed in both groups, a faster normalization to pre-challenge
values for TNF alpha, IL-6, IL-8, IL-10 and p53 was observed in the La1 group compared to placebo. We show that La1 limits UVinduced
immune-suppression and skin infl ammation thus contributes to the early recovery of the skin immune homeostasis. In a last
study, we evaluate the effi cacy of La1 supplementation on UV suppression of CHS response and found that La1 protect against UV
suppression of skin immune response. All these studies confi rm that La1 supplementation signifi cantly protects the skin’s immune
system from UV-induced immunosuppression. Maintenance of the cutaneous immune response is valuable in preventing long-term
eff ects of UV radiation, such as tumour development, which can result when there is a lack of appropriate immune-surveillance.