The labial salivary glands (LSG) of primary SS exhibit increased IL-21 and IL-21 receptor expression. Shown is the expression of the IL-21 and IL-21 receptor in the labial salivary glands of control subjects (n = 4; upper panel) and patients with primary SS (n = 16; lower two panels), as determined by immunostaining using specific antibodies. The cells that stained with the antibodies appeared in brown. (a) The infiltrating lymphocytes and periductal areas of the patients with SS exhibited intense IL-21 staining, whereas there was no staining with the isotype controls. (b) The lymphocytic infiltrations and periductal areas stained for IL-21 receptor. In contrast, the control subjects did not exhibit any IL-21 or IL-21 receptor expression in their labial salivary glands. IL: Interleukin; LSGs: labial salivary glands; SS: Sjögren's syndrome.