CD27+IgD+B cells are less competent in producing IgM in SLE
To examine CD27+IgD+B cells’ functional changes, their ability to produce IgM was assessed in SLE patients. CD27+IgD+B cells isolated from active SLE cases (SLEDAI>5) and HCs underwent ELISPOT and qRT-PCR. As depicted in Figure 3A, ELISPOT revealed significantly reduced IgM-producing ability for CD27+IgD+B cells in SLE, which was confirmed by decreased IgM mRNA levels as examined by qRT-PCR (Figure 3B). Jointly, the above data indicated that CD27+IgD+B cells had impaired function regarding IgM production in SLE.
CD27+IgD+B cells are recovered in SLE cases with treatment-related disease remission
To ascertain CD27+IgD+ B cells’ usefulness as a biomarker of disease activity, whether they are restored following effective treatment was assessed. Totally 12 patients previously diagnosed with SLE were assessed during relapse and 4 weeks post-treatment initiation. As expected, treatment markedly decreased disease activity based on the SLEDAI (Table 2). In addition, anti-dsDNA and 24h urinary protein amounts were reduced, with serum C3 and C4 level normalization to a certain degree. Total leukocyte and platelet levels were heightened post-treatment.
Next, CD27+IgD+B cell amounts were assessed pre-treatment and at 4 weeks post-treatment initiation (Figure 4A). As measured by the SLEDAI, all cases had a significant reduction in disease activity after treatment (Figure 4B); meanwhile, CD27+IgD+B cell amounts were remarkably elevated (Figure 4C). Jointly, the above findings suggested that CD27+IgD+ B cell amount impairment in SLE patients could be alleviated by effective treatment.