Rationale for treating primary Sjogren's syndrome patients with an anti-CD6 monoclonal antibody (Itolizumab)

CD6 is a cell surface receptor expressed on the majority of T cells and a subset of B cells. When expressed, CD6 contributes to lymphocyte activation through its extracellular domain 1, while adhesion and cellular migration are related to the extracellular scavenger receptor cysteine-rich domain (SRCR-D)-3 of CD6. Itolizumab, clone T1h, is a newly developed humanized IgG1 monoclonal antibody that targets CD6 SRCR-D1 and blocks immune activation. Itolizumab has been proposed to be effective in autoimmune diseases such as rheumatoid arthritis, Sjogren's syndrome and multiple sclerosis. In Sjogren's syndrome, the utilization of itolizumab as therapeutic option is reinforced by our recent observation that ALCAM, the CD6 ligand, is overexpressed and that CD6-positive T and B cells are detected within salivary glands from Sjogren's syndrome patients. In this study, itolizumab-positive target cells were characterized within both peripheral blood and salivary glands in order to provide rational for anti-CD6 treatment in Sjogren's syndrome.