CD19 and type 1 diabetes mellitus: To investigate transcriptional, phenotypic, and immune repertoire changes within B cell subsets, we flow cytometry purified live, singlet, CD19+ cells from the peripheral blood of n = 9 Stage 1 T1D (≥2/5 islet autoantibodies, normal OGTT results) and n = 8 non-diabetic, first-degree relative (healthy) controls (Table 1), as in Methods.