reduced the number of recruited MDSCs
The above results showed that IL-35 had a clear effect in treating
psoriasis and MDSCs were significantly expanded in patients with
psoriasis and the mouse model. To test whether IL-35 ameliorates
psoriasis by restricting the accumulation of MDSCs, we used flow
cytometry to analyse the number of MDSCs in mice with IMQ-induced
psoriasis
with or without treatment of IL-35. The results showed that compared
with that in the control group, administration of IL-35 reduced the
infiltration of MDSCs in the spleen and skin tissues of mice
(Fig.
5A and B).
Then,
we investigated whether the populations of G-MDSCs and M-MDSCs were
altered in response to this therapy stress.
We
found that both G-MDSC and M-MDSC populations were significantly reduced
in both the spleen and skin tissues (Fig. 5C-E). Finally,
immunofluorescence staining of
CD11b+Gr-1+ MDSCs in the inflamed
skin showed that the MDSC
accumulation was inhibited by IL-35 treatment (Fig. 5F).
These
results demonstrated that the immunosuppressive effect of IL-35 on the
IMQ-induced psoriasis model was achieved by reducing the infiltration
and proportion of MDSCs, and it can adjust the proportion of MDSC
subtypes. Next, we examined whether IL-35 directly affects the
differentiation and recruitment of MDSCs in vitro using
fluorescence-activated cell sorting (FACS). IL-35 had little effect on
the differentiation of MDSCs
(Supplementary
Fig. 3A, B IL-35 also did not significantly affect the numbers of
G-MDSCs and M-MDSCs cells (Supplement Fig. 3C-E).
3.6Adoptive
transfer of MDSCs weakened the effect of IL-35 in mice withIMQ-induced
psoriasis
To further explore whether the therapeutic effect of IL-35 was related
to MDSCs,
MDSCs
from
IMQ-induced mice were adoptively transferred following the experimental
schedule (Fig. 6A). We found that
the
adoptive transfer of MDSCs derived from IMQ-induced mice aggravated
disease
progression. Moreover, when these MDSCs were transferred to the
IL-35-treated group, the psoriasis symptoms were aggravated in these
mice compared with those in mice treated with IL-35 alone (Fig. 6B). We
evaluated pathological features in mice, such as erythema, scaling, and
thickness, in different groups
using
the PASI scoring system (Fig. 6C). We observed that compared with the
control (PBS) group, the PBS + MDSC group exhibited a higher PASI score.
Similarly, the score of the IL-35 + MDSC group was significantly higher
than that of the group treated with IL-35 alone. Furthermore, we
calculated the cumulative scores from different groups and found that
the IL-35-treated group exhibited the lowest cumulative scores than the
other groups (Fig. 6C).
H&E-stained skin sections from these groups exhibited increased
epidermal thickening in PBS + MDSC group relative to that in the control
group. We also found that the skin epidermis in IL-35 + MDSC group was
significantly thicker than that in the IL-35-treated group (Fig. 6D). In
addition, the Baker system-based score of the IL-35-treated group was
the lowest of these four groups (Fig. 6E).
3.7IL-35
inhibited the expression of iNOS in MDSCs in mice with IMQ-induced
psoriasis
The above results indicated that IL-35 inhibits the recruitment of
MDSCs. Next, we investigate whether IL-35 affects the expression of
inflammatory mediators in MDSCs. We used flow cytometry to analyse the
expression of iNOS and IL-10, which were secreted by MDSCs in mice with
IMQ-induced psoriasis with or without treatment of IL-35. The results
showed that compared with the control group, the IL-35-treated group
exhibited reduced expression of iNOS in the spleen and skin tissues
(Fig. 7A and B). However, there was no difference in the level of IL-10
(Fig. 7C and D). Finally, immunofluorescence staining of
iNOS+Gr-1+ MDSCs in the inflamed
skin showed that the iNOS+Gr-1+ MDSC
accumulation was inhibited by IL-35 (Fig. 7E).