Infection in patients with systemic lupus erythematosus

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Abstract
We have found subnormal amounts of chemotactic activity in zymosan-treated sera from 13 of 29 patients with systemic lupus erythematosus (SLE). As an explanation for this abnormality, the presence of a uniquely specific, heat-stable inhibitor of complement (C5)-derived chemotactic activity has been documented in sera from 11 of these patients. Sera from 2 other patients contained elevated levels of nonspecific, heat-labile chemotactic factor inactivator (CFI) activity. The serum from 1 patient contained the heat-stable inhibitor as well as elevated levels of CFI. Patients with SLE whose sera contained the heat-stable inhibitor had more active disease clinically, but otherwise they were indistinguishable from patients without the inhibitor. When patients with the heat-stable inhibitor improved clinically, this usually was accompanied by a decrease in serum inhibitory activity. Only one episode of bacterial infection was observed among 16 patients with SLE whose sera yielded normal amounts of chemotactic activity after treatment with zymosan. In contrast, 7 of 11 patients with SLE whose sera contained the heat-stable inhibitor suffered serious bacterial infections. The presence of this heat-stable inhibitor in sera from some patients with SLE may contribute, in part, to their increased susceptibility to infection.