CD27 and systemic lupus erythematosus: The proportion of CD27+IgD+ B cell in patients with lupus nephritis (n = 10, median 5.0% (range: 2.0–11.1)) was lower than those in SLE patients without renal involvement (n = 7, median 11.9% (range: 4.7–32.6)) (P = 0.032) (Figure 1(a)).