A method of preparing an injection solution includes: (1) storing a mixture of a blood sample and a divalent cation chelating agent at a temperature between 2 and 12 degrees Celsius for a period of from 3 hours to 72 hours so as to have the mixture with two or more separate layers, wherein a liquid in one of the separate layers contains small somatic stem cells such as SB cells； (2) collecting the liquid from the mixture； and (3) after collecting the liquid from the mixture, mixing the liquid with a solution free from Ca2+ into the injection solution. The injection solution can be used for an autoimmune disease, such as ankylosing spondylitis, rheumatoid arthritis, or Grover's disease.
