Considerably a higher number of CD19+ B lymphocytes, CD3+CD4+ T and CD3+CD8+ T lymphocytes and a lower number of NK cells of patients with newly diagnosed type 1 diabetes in the absence of significant changes in the number of these cells in chronic patients’ cases confirm the thesis of participation of these cells in early stage of the disease, which may contribute to the destruction of pancreatic beta cells. The gene discussed is CD19; the disease is type 1 diabetes mellitus.