Immunoglobulin secretion from CD3-CD38bright cells in bone marrow. (A) Fresh bone marrow-derived mononuclear cells (BMMCs) were stained with PerCP cyanin 5.5 dye for flow cytometric cell sorting (FL2H) according to immunoglobulin D (IgD) phycoerythrin and CD38 expression, resulting in four populations: CD38low cells, IgD+CD38high cells, IgD-CD382+ cells and IgD-CD38bright cells. These cell populations were incubated on precoated ELISPOT plates as described in the Methods section. (B) Using the enzyme-linked immunosorbent spot assay, we detected the number of spot-forming units (SFUs) and quantified them for the IgG, IgM and IgA isotypes. PBS = phosphate-buffered saline. Bars represent means ± SEM of five experiments. (C) Calculated total number of SFUs for total immunoglobulin (total Ig) secretion. (D) 2 × 2 table showing the sensitivity and specificity of the population of CD3-CD38bright cells to secrete immunoglobulins. The sensitivity was 92.9%, and the specificity was 53.6%. FACS = fluorescence-activated cell sorting.