CD11b⁺ human B1 cells are increased and functionally altered in patients with systemic lupus erythematosus. (A and B) Adult peripheral blood mononuclear cells from normal individuals and from patients with SLE were immunofluorescently stained for CD20, CD27, CD43, and CD11b, and were then evaluated by flow cytometric analysis. Expression of CD11b is shown (black lines) on gated CD20⁺CD27⁺CD43⁺ B1 cells from a representative normal individual from among the 67 normal controls (A) and a representative SLE patient (B) with isotype control in solid gray. (C) Adult peripheral blood mononuclear cells from patients with SLE and from normal individuals were immunofluorescently stained for CD20, CD27, CD43, and CD11b, and were then evaluated by flow cytometric analysis. The percentages of naive B cells (CD20⁺CD27⁻CD43⁻), memory (mem) B cells (CD20⁺CD27⁺CD43⁻), CD11b⁻ (11b⁻) B1 cells (CD20⁺CD27⁺CD43⁺CD11b⁻), and CD11b⁺ (11b⁺) B1 cells (CD20⁺CD27⁺CD43⁺CD11b⁺), among all B cells in SLE patients (n = 15), were compared with the percentages of these populations among all B cells in normal controls (n = 67). Ratios between these values are expressed as fold change for B cell populations in SLE patients versus normal controls along with lines indicating SEM. (D and E) Adult peripheral blood mononuclear cells from 15 lupus patients were immunofluorescently stained for CD20, CD27, CD43, CD11b, and CD86 and were then evaluated by flow cytometric analysis. (D) Mean values for the proportion of CD86⁺ cells among naive B cells (CD20⁺CD27⁻CD43⁻), memory (mem) B cells (CD20⁺CD27⁺CD43⁻), CD11b⁻ (11b⁻) B1 cells (CD20⁺CD27⁺CD43⁺CD11b⁻), and CD11b⁺ (11b⁺) B1 cells (CD20⁺CD27⁺CD43⁺CD11b⁺) are shown with lines indicating SEM (n = 15). (E) CD86 mean fluorescence intensity (MFI) was evaluated for CD11b⁺ B1 cells from 15 randomly selected samples from among the 67 normal control (normal) and 15 lupus patient (SLE) adult peripheral blood samples. Mean values are displayed along with lines indicating SEM. (F) Sort-purified and irradiated CD11b⁺ B1 cells (CD20⁺CD27⁺CD43⁺CD11b⁺) from three randomly selected samples from among the 67 normal control (normal) and 3 lupus patient (SLE) peripheral blood samples were cultured 1:2 in triplicate with negatively selected allogeneic CD4⁺ B cells for 5 d, after which proliferation was measured by incorporation of tritiated thymidine. Mean cpm values are shown along with lines indicating SEM.