['Minimal change disease (MCD) is the most common cause of nephrotic syndrome in children and is associated with the expression of CD80 in podocytes and the increased excretion of CD80 in urine. We hypothesized that serum from patients with MCD might stimulate CD80 expression in cultured podocytes.', 'Sera and peripheral blood mononuclear cells (PBMCs) were collected from subjects with MCD in relapse and remission and from normal controls. Immortalized human podocytes were incubated with culture media containing patient sera or supernatants from patient and control PBMC cultures. CD80 expression was measured by quantitative PCR and western blot analysis.', 'Sera collected from patients with MCD in relapse, but not in remission, significantly increased CD80 expression (mean ± standard deviation: 1.8\u2009±\u20090.7 vs. 0.8\u2009±\u20090.2; p\u2009<\u20090.004) and CD80 protein secretion by podocytes (p\u2009<\u20090.05 between relapse and normal controls). No such CD80 increase was observed when podocytes were incubated with supernatants of PBMC cultures from patients in relapse.'] Does serum from minimal change patients in relapse increase CD80 expression in cultured podocytes?