Higher secretion of Th1- and Th17-typical cytokines or
expression of Th17 molecular markers in cells of
CD26high group
To investigate the association of CD26 expression with CD4 cell
differentiation, the percentages of T helper subpopulations were
determined by flow cytometry after cells were labeled with
fluorescence-conjugated antibodies against corresponding cytokines or
cell surface markers. The results showed that the percentages of cells
secreting Th1-typical cytokine IL-2 and IFN-γ in the
CD26high group were significantly higher than those in
the CD26low group (Figure 5A) . The percentage
of cells secreting IL-2 in the CD26high group was
approximately three times that of the CD26low group
(25.93±5.39% vs. 8.89±5.85%), and the percentage of cells
secreting IFN-γ in the CD26high group was about seven
times that of the CD26low group (30.17±11.14%vs. 4.45±2.63%). Similarly, in Figure 5B , the
percentages of cells secreting Th17-typical cytokines (IL-6, IL-17,
IL-22) or expressing biomarkers (IL-23R, CD196 and CD161) were evidently
higher in the CD26high group than in the
CD26low group. The percentages of cells secreting IL-6
or lL-17 in the CD26high group were about 7-fold of
that in the CD26low group (28.11% vs. 4.12%,
31.28% vs. 4.32%). The percentage of cells secreting IL-22 in
the CD26high group was 5.4-fold compared to the
CD26low group (31.05% vs. 5.74%). The
percentage of cells expressing IL-23R was even higher in the
CD26high group, 7-fold of that in the
CD26low group (35.93% vs. 4.98%). In
addition, the percentages of cells expressing Th17 surface biomarkers
CD196 and CD161 in the CD26high group were 2.8-fold
and 3-fold of that in the CD26low group (34.73%vs. 12.35%, 42.52% vs. 13.59%), respectively. Histogram
analysis showed that the expression levels of Th1 and Th17 typical
cytokines (IL-2, IFN-γ, IL-6, IL-17, IL-22) or a Th17 typical surface
marker (IL-23R) in the cells of the CD26high group
were much higher in relation to the cells of CD26lowgroup (Figure 5C) . These results suggest that the expression of
CD26 is involved in the regulation of the differentiation and functions
of Th1 and Th17 subpopulations of T lymphocytes.
On the other hand, the percentages of cells secreting Th2-typical
cytokines either IL-4 or IL-13 showed exceptionally low and no
significant differences between the CD26high group and
the CD26low group (Figure 5A) . Similarly, the
histogram analysis showed that there were no significant differences in
the expression levels of Th2 cytokines (IL-4 and IL-13) in cells between
the CD26high group and the CD26lowgroup (Figure 5C) . In addition, the percentages of cells
expressing molecular markers of regulatory T cells
(CD25+Foxp3+ or
CD4+Foxp3+) in the
CD26high group did not have significant differences to
that in the CD26low group (Figure 5D) . These
results suggest that the CD26 expression is not correlated to the
differentiation and functions of Th2 and Tregs subpopulations of T
lymphocytes after antigen stimulation.