PTX3 and systemic lupus erythematosus: Analyses of B cell subsets confirmed a substantial decrease in absolute numbers of both naïve (CD20+CD27−) and memory (CD20+CD27+) PTX3+ B cells in LN compared to HD and non-renal SLE patients (mean ± SD naïve/ml: LN 0.18 ± 0.58 vs. HD 30.12 ± 42.96, p = 0.0001; LN SLE 0.18 ± 0.58 vs. non-renal 16.22 ± 24.88, p = 0.028; mean ± SD memory/ml: LN 0.97 ± 2.18 vs. HD 12.75 ± 24.88, p = 0.011; LN 0.97 ± 2.18 vs. non-renal SLE 4.07 ± 5.21, p = 0.038) (Figure 2A, middle and right).