Scatter plots for cell populations that demonstrated significant differences between first-degree relatives and control individuals. Peripheral blood mononuclear cells were stained with various combinations of conjugated mAbs, fixed, and analyzed by flow cytometry (as outlined in the Materials and methods section and shown in Figure 1). (a) Shown are plots for the proportion of activated naïve B cells (CD20+CD27- cells that were CD86+), the proportion of B cells (CD20+) that had a mature naïve phenotype (CD27-CD38-/+), the proportion of NKT cells (CD3+ cells that were Vα24+Vβ11+), and the proportion of memory CD4+ T cells (CD45RA-CD45RO+). Results shown are for 144 (143 for NKT cells) lupus probands, 356 family (parents and siblings) members (355 for NKT cells), 287 parents (286 for NKT cells), 69 siblings, and 102 control individuals. (b) The proportion of NKT cells in controls, probands, and family members, stratified for the presence or absence of positive ANA status. Significant differences (*P < 0.05, **P < 0.005, and ***P < 0.0005) were determined using the Wilcoxon test. In panel a differences are as compared with control individuals, and in panel b comparisons are between indicated populations. mAb, monoclonal antibody; NK, natural killer.