Presence of C5a‐potentiating activity in the plasma of a patient with Kimura's disease

Abstract

To determine whether the response to the active complement fragment C5a in polymorphonuclear leukocytes (PMN) obtained from a patient with Kimura's disease is similar to that in normal subjects, we evaluated superoxide anion (O2-) generation after stimulation with C5a. The patient's PMN produced more O2- than did those from healthy controls after stimulation with human C5a in vitro. The response returned to normal with the improvement in clinical indicators after initiation of steroid administration. We conducted the following experiments with the plasma of this patient during the active disease stage to establish the presence of a humoral factor that potentiated the C5a-response of PMN. Incubation of PMN from normal controls having the same blood type as the patient at 37 degrees C for 2 h with the patient's plasma at the active disease stage revealed that the cells generated abundant O2- after stimulation with C5a. Incubation of normal PMN with the patient's plasma during the inactive disease stage showed no potentiated response to C5a. This activity was lost after incubation at 56 degrees C for 30 min. Coincubation of PMN with methylprednisolone up to 100 micrograms/ml did not suppress this activity. Although the plasma concentration of C5a at the active stage was mildly elevated (13 ng/ml), it was below the limit of detection (< 10 ng/ml) at the inactive stage. These results suggest the presence of a heat-labile, humoral factor in the patient's plasma that upregulated the response of PMN to C5a and that was not suppressed by in vitro treatment with a steroid. This factor may influence the acute inflammatory reaction in this disorder.