CD40 and systemic lupus erythematosus: Because we found greater variability in the CD40 expression of pDCs from old mice with lupus than from the other groups of mice, we take into account that technical reasons may have hampered the statistical significance in this comparison (Kruskal-Wallis p = 0.018, Mann-Whitney NZM versus BALB/c = 0.064, NZM versus B6 = 0.023).