Figure 7. TLR stimulation of healthy Black and White immune cells recapitulates ancestry-associated SLE immunophenotypes.

One million PBMCs from 10 White and 10 Black healthy controls, devoid of any autoimmune characteristics (ANA^–, RF, CCP3 antibody negative, and negative CSQ), were stimulated with R848 (TLR7/8 agonist), CpG (TLR9 agonist), or IFN-α alone or in combination for 7 days and analyzed by flow cytometry. (A) tSNE plots identified 9 different immune cell populations across samples. (B) Representative tSNE plots of healthy White and Black cells following the 9 different stimulation conditions. CD38 expression is shown from red (high expression) to blue (low expression). Cells were counted in culture following 7-day stimulation, and total cell subset numbers were back-calculated using cell frequencies. The total (mean ± SD) (C) T cells, (D) NK cells, (E) B cells, and (F) myeloid cells/mL are shown for the 8 different stimulations by ancestry. (G) B cells were further subdivided by biaxial gating on IgM and CD27 to assess 6 different B cell subsets: 1) class-switched plasmablasts, 2) IgM⁺ plasmablasts, 3) class-switched memory B cells, 4) IgM⁺ memory B cells, 5) DN B cells, and 6) naive B cells. The frequency (mean ± SD) of (H) naive B cells, (I) DN B cells, (J) class-switched memory B cells, and (K) class-switched plasmablasts is shown for each condition. Supernatants were collected and assessed via ELISA for (L) total IgG concentrations and (M) IgA concentrations. Statistical significance was determined using a Mann-Whitney U test (P < 0.05), and all FDR q values were used for multiple comparisons.