Immune abnormalities and clinical course in childhood IgA nephropathy.

Immunoglobulin production by peripheral blood mononuclear cells (PBMC) and lymphocyte subpopulations were studied in 56 children with IgA nephropathy (IgAN) and 22 healthy controls. All the patients had persistent proteinuria at the time of diagnosis, and were divided into three clinical groups on the basis of urinary findings at the time of examination: 27 patients had proteinuria with or without microscopic hematuria (group A; active stage), 9 had microscopic hematuria only (group B; healing stage) and 20 had normal urine (group C; remission stage). PBMC from the patients in group A cultured without mitogenic stimulation produced significantly more IgA and IgG than those from controls (p less than 0.05). After polyclonal B cell stimulation with pokeweed mitogen (PWM), PBMC from patients in group A produced significantly more IgA than those from group B (p less than 0.05), group C (p less than 0.05) or controls (p less than 0.01), and produced significantly more IgG than those from group B (p less than 0.05) or controls (p less than 0.01). However, there was no significant difference in PWM-stimulated IgG production between groups A and C. PWM-stimulated PBMC from patients in group C produced significantly more IgA and IgG than those from controls (p less than 0.05). There were no significant differences in lymphocyte subpopulations among groups A, B and C and controls. These findings show that the clinical course of childhood IgAN is correlated with IgA production by PBMC suggesting that overproduction of IgA might be responsible for the pathogenesis of IgAN in children.