Lymphocyte suppressor-cell function was studied by induction with
concanavalin A in 31 patients with
minimal-change nephropathy (MCN) in remission. 21 patients had been treated with
cyclophosphamide 0.5--12.0 years previously (mean 6.5 years) and had been in remission for 0.5--9.0 years (mean 5.1 years). The remaining 10 patients had never received
cyclophosphamide and had been in remission for 1--10 years (mean 5.3 years). The
cyclophosphamide-treated group had significantly less suppressor-cell function than either the controls or the non-
cyclophosphamide-treated group, the latter being not significantly different from normal. When patients who had received
cyclophosphamide were divided into those who had relapsed after taking this
drug (10 patients) and those who had not (11 patients), suppressor-cell function was significantly impaired in the non-relapsing group. This association of impaired suppressor-cell function with failure to relapse may indicate that suppressor cells have a pathogenetic role in MCN and that the
therapeutic effect of
cyclophosphamide in this disease is to diminish their function. Alternatively, the impaired suppressor-cell function in the non-relapsing group may be simply a marker of effective treatment with
cyclophosphamide. The finding of long-term suppression of lymphocyte function after
cyclophosphamide coupled with this
drug's risks of causing
malignancy and gonadal dysfunction reinforces the need for caution in its use in MCN.