CD19⁺ASCs are the most common immunoglobulin-secreting cells in BM and spleen. (A) Cytoplasmic immunoglobulin immunophenotyping gated on CD38^highCD27⁺ ASCs. Representative plots showed CD19⁺ and CD19⁻ vs cytoplasmic immunoglobulin in BM and spleen. (B) Relative frequency of immunoglobulin-secreting isotypes among ASC CD19⁺ or CD19⁻ from BM (n = 8) and spleen (n = 7). (C) The frequency between CD19⁺ and CD19⁻ ASCs for immunoglobulin isotype secretion via cytoplasmic immunoglobulin FCM in BM (upper, unpaired Student t test, IgG P < .0002, CD19⁺ mean ± SEM 39.58 ± 3.952, CD19⁻ mean ± SEM 13.18 ± 2.473, n = 6, IgM P < .043, CD19⁺ mean ± SEM 4.393 ± 1.359, CD19⁻ mean ± SEM 1.095 ± 0.4234, n = 6) and spleen (lower, Student unpaired Student t test, IgG P < .0001, CD19⁺ mean ± SEM 40.78 ± 2.48, CD19⁻ mean ± SEM 11.54 ± 2.515, n = 6, IgM P < .0179, CD19⁺ mean ± SEM 8.665 ± 2.491, CD19⁻ mean ± SEM 1.515 ± 0.4246, n = 6, IgA P < .0035, CD19⁺ mean ± SEM 10.3 ± 2.242, CD19⁻ mean ± SEM 1.686 ± 0.3156, n = 6) immunoglobulin isotype testing via cytoplasmic immunoglobulin FCM. (D) Immunoglobulin secretion by ELISpot showed no significance between CD19⁺ and negative ASCs in BM (upper, IgG n = 13, IgM n = 6, IgA n = 6) or spleen (lower, IgG n = 8, IgM n = 6, IgA n = 7). (E) Representative ELISpots are shown for both BM (upper) and spleen (lower). Cyto, cytoplasmic; Ig, immunoglobulin.