In addition, although the number of total PBDCs and myeloid DCs was decreased significantly in secondary SS patients, the number was distributed more widely than that in primary SS patients (Fig. 2a,b). Based upon these findings, we hypothesized that the number of PBDCs in secondary SS might

be influenced or determined by the autoimmune diseases that overlap with SS. Therefore, we compared the number of total PBDCs, myeloid DCs and plasmacytoid DCs in each subgroup of secondary SS (five SLE-merged secondary SS, 11 RA-merged secondary SS and eight SSc-merged secondary SS) with that in each corresponding primary autoimmune disease and in normal controls. There was no significant difference in the number of total PBDCs, myeloid DCs and plasmacytoid DCs

among SSc-merged secondary SS (total PBDCs: mean 17 855/ml; myeloid DCs: mean 8959; plasmacytoid selleck compound DCs: mean 8897), RA-merged secondary SS (total PBDCs: mean 15 866; myeloid selleck screening library DCs: mean 8137; plasmacytoid DCs: mean 7729) and normal controls. PBDCs, myeloid DCs and plasmacytoid DCs were all decreased significantly in SLE-merged secondary SS (total PBDCs: mean 6358; myeloid DCs: mean 2863; plasmacytoid DCs: mean 3495) (Table 1). The number of total PBDCs, myeloid DCs and plasmacytoid DCs in each subgroup of secondary SS was similar to that in the corresponding primary autoimmune disease that overlaps in each subgroup of secondary SS. Furthermore, we analysed the PBDC numbers of primary SS and secondary SS which were compared with RA and SLE. The total numbers of PBDC and myeloid DC were decreased significantly in primary and secondary SS patients in comparison with RA, which was similar

to healthy donors, but not with SLE (Fig. 2a,b). Meanwhile, the numbers of total PBDCs and plasmacytoid DCs in secondary SS were significantly larger than those in SLE. These results might be due to the decreased plasmacytoid DCs in SLE. The decreased number of PBDCs in primary SS is restored naturally during the clinical course. In our previous report, we put forward a hypothesis that the decrease of PBDCs might be a critical most event in the pathogenesis of primary SS [2]. Thus, in this study we examined whether the decrease of PBDCs continues during the natural course of primary SS. As shown in Fig. 3a–c, a direct correlation was observed between the number of PBDCs and the time from onset of Sicca syndrome in primary SS. None of the 29 patients received therapeutic agents, including corticosteroids. In addition, six of the 29 patients with primary SS were examined twice sequentially for PBDC numbers (Fig. 3g–i). Four of the six patients and all six patients showed an increase in the number of total PBDCs and myeloid DCs, respectively, after an average of 43 months from the initial examination. However, plasmacytoid DC numbers did not show a distinct alteration in all the six patients.