Decreased lymphocyte reactivity to a suboptimal concentration of phytohemagglutinin in Sjögren's syndrome.

Significantly decreased lymphocyte reactivity to a suboptimal concentration of phytohemagglutinin (PHA) was found in patients with Sjögren's syndrome (SS), whereas the response to an optimal concentration was generally normal. Kinetic studies were performed on control lymphocytes. Only suboptimal PHA concentrations stimulated tritiated thymidine (3H-TdR) incorporation in proportion to the number of potentially reactive lymphocytes. Kinetic studies of SS patients suggested that their low reactivity was attributable to fewer functionally reactive lymphocytes rather than to a decreased rate of proliferation.