Late (CD45RA+CD28–) effector CD8 cells express CD146. Collectively, these findings suggest two

modes of CD146 expression: one that is related closely to recent or chronic memory T cell activation and predominates in healthy donor CD4 T cells, and another, which appears to be more stochastic and predominates in the CD8 subset. Consistent with previous reports [11], circulating T cells in patients with sSS were phenotypically activated (increased CD25, OX40, and perhaps CD69), both in the CD4 and the CD8 subset. The increased frequency of CD146-expressing CD4 and CD8 cells in these patients, as well as the correlation with several activation markers, is consistent with this. Combinatorial analysis of activation markers Natural Product Library research buy including CD146 may improve the assessment of T cell activation in CTDs. Importantly, CTD patients in general maintain normal or slightly reduced lymphocyte counts in blood [10, 11]; PBMC yields (by haemocytometer counting) were not markedly abnormal in our CTD patients. Unexpectedly, activation markers were not increased in T cells

from our SLE and most pSS patients. This contrasted with previous studies, in which increased frequencies of recently and chronically activated and senescent T cells were found in patients with SLE [10] R428 datasheet or pSS [34-37], including patients studied by us (C. Bryson, F.C. Hall, unpublished observations). Most of the patients examined in the present study lacked critical organ involvement and had mild or moderate disease activity. Their disease was well controlled by drug therapy, ranging from hydroxychloroquine alone to various combinations of anti-proliferative agents, corticosteroids and biologicals (Supporting information, Table S1). This might account for their non-activated peripheral T cell phenotypes and low CD146 expression. This is not a sensitivity issue, as we detected T cell activation and CD146 up-regulation in sSS, and more recently in a separate study of patients with inflammatory arthritis, using the same reagents and protocols (C. Wu, R. Busch, J.S.H. Gaston, unpublished data). As a result of the unexpected non-activated

phenotypes in these patients, this study cannot address whether CD146 up-regulation is a disease-specific feature of sSS or a consequence Hydroxychloroquine concentration of systemic hyperactivity, which happened to be detectable only in sSS patients in our study. The latter explanation is, however, both more conservative and plausible. A much larger multivariate analysis of CTD patients with diverse diagnoses, varying in T cell activation, would be required to address this fully and to account for confounding variables. Our unpublished work (C. Wu et al.) also confirms previous findings (cf. Introduction) that CD146+ CD4 cells are strongly enriched for Th17 cells [CCR6+, CD161+; mitogen-stimulated interleukin (IL)-17 and IL-22 secretion].