Use of Jack bean lectin or a pharmaceutically acceptable salt thereof for increasing the abundance of hematopoietic stem cells and progenitor cells in bone marrow and/or epidermal stem cells in skin in vivo and a method of treatment involving the said lectin at a specific dose to treat conditions due to depletion of stem cells. Method of treating said conditions in a subject by administering a single injection of lectin dose 0.5-2.0 mg/kg body weight to mouse for increasing the abundance of skin stem cells from 2.815±0.100% (mean±SEM) in control untreated mice to 8.097±0.938% and 9.993±0.542% in mice treated with lectin dose of 0.5 mg/kg body weight and 2 mg/kg body weight respectively; and a dose range 8.0-10 mg/kg body weight to mouse for increasing the abundance of hematopoietic stem cells in bone marrow from 0.293±0.043% (mean±SEM) in control untreated mice to 1.956±0.592% and 0.692±0.193% in mice treated with lectin dose of 8.0 mg/kg body weight and 10 mg/kg body weight respectively.