Abstract: Objective To investigate the effect of oral administration of Zaocys type II collagen (ZCII) on the percentages of Treg/
Th17 cells in mesenteric lymph node lymphocytes (MLNLs) in mice with collagen-induced arthritis (CIA). Methods CIA was
induced in male C57BL/6 mice by immunization with chicken type II collagen. Three weeks later, ZCII, purified by pepsin
digestion, was orally administered in the mice for 7 consecutive days (daily dose of 10, 20, or 40 μg/kg). The severity of
arthritis in each limb was evaluated using a macroscopic scoring system, and histopathological changes of the joint were
observed microscopically with HE staining. The percentages of Treg and Th17 cells in MLNLs was detected by flow cytometry,
and the levels of transforming growth factor-β (TGF-β) and interleukin-17 (IL-17) in the supernatant of MLNLs were measured
by enzyme-linked immunosorbent assay. Results Compared with normal control mice, the mice with CIA had significantly
higher scores for arthritis and histopathological changes, with also significantly increased percentages of Treg and Th17 cells in
MLNLs and elevated levels of TGF-β and IL-17 in MLNL supernatant (P<0.05). In ZCII peptide-treated mice, the scores for
arthritis and histopathological changes were significantly lower than those in CIA model group (P<0.05), and Treg cell
percentage in MLNLs was up-regulated while Th17 cell percentage lowered; the level of TGF-β was increased but IL-17 was
decreased significantly (P<0.05). Conclusion Oral administration of ZCII improves CIA in mice by regulating the percentages
of Treg/Th17 cells and the cytokine levels in MLNLs, suggesting the value of ZCII as a promising candidate agent for treatment
of rheumatoid arthritis.