Changes of memory B- and T-cell subsets in lupus nephritis patients.

INTRODUCTION Renal involvement in systemic lupus erythematosus (SLE) is associated with production of antibodies to double stranded DNA, deposition of immune complexes and organ damage. These processes have been linked with abnormalities in B- and T-cell memory compartments. The aim of the study was to analyze subsets of peripheral memory B-cells and T-cells in lupus nephritis (LN) patients. MATERIAL AND METHODS We used multicolor flow cytometry to analyze major memory subsets of peripheral blood B-cells (defined by CD27, IgD and CD21) and T-cells (CD45RA, CD45RO, CCR7) in 32 patients with active or inactive LN, and 23 control subjects. RESULTS Lupus nephritis patients were characterized by increased percentage of immature/early-transitional B-cells (CD27-IgD+CD21-), higher frequency of activated switched memory (SM, CD27+IgD-CD21-) and exhausted memory B-cells (CD27-IgD-), and decrease in non-switched memory (NSM, CD27+IgD+) B-cells. CD21low subsets (immature and activated B-cells) were particularly expanded in patients with active disease. In both groups of LN patients we observed decline in the absolute count of NSM B-cells. It was paralleled by lymphopenia in naïve CD4+ T-cell compartment and increase in the frequency of effector memory T-cells, and these changes were more pronounced in active LN. CONCLUSIONS B-cell memory compartment in LN is deficient in NSM cells and during active disease it is further skewed towards SM and exhausted memory phenotypes, most likely as a cause of chronic antigenic stimulation. Parallel changes in T-helper cell subsets suggest a similar mechanism of SLE-related lymphopenia for both B-cell and T-cell compartment.