Tehran University of Medical Sciences Iranian Journal of Allergy, Asthma and Immunology 1735-1502 21 6 2022 12 24 670 676 Shaghayegh Pezeshki Department of Immunology, School of Medicine, Iran University of Medical Sciences, Tehran, Iran Mir Hadi Jazayeri Department of Immunology, School of Medicine, Iran University of Medical Sciences, Tehran, Iran AND Immunology Research Center, Institute of Immunology and Infectious Diseases, Iran University of Medical Sciences, Tehran, Iran Bahram Chahardouli Hematology, Oncology and Stem Cell Transplantation Research Center, Tehran University of Medical Sciences, Tehran, Iran Nader Tajik Department of Immunology, School of Medicine, Iran University of Medical Sciences, Tehran, Iran AND Immunology Research Center, Institute of Immunology and Infectious Diseases, Iran University of Medical Sciences, Tehran, Iran Seyyed Massood Nabavi Department of Regenerative Medicine, Royan Institute for Stem Cell Biology and Technology, ACECR, Tehran, Iran Mahdi Akbarzadeh School of Nursing, Baqiyatallah University of Medical Science, Tehran, Iran 2022 08 06 2022 09 04 Chronic lymphocytic leukemia (CLL) is the clonal expansion of mature CD5+ B cells and the most common lymphoproliferative disease in adults (B1-CLL). B1 cells' anti-inflammatory effects include the production of natural IgM (nIgM) by the spleen and bone marrow, decreased inflammatory cytokines as a primary response to maintaining tissue homeostasis, and enhanced release of transforming growth factor β (TGFβ). We used the flow cytometry technique in peripheral blood from patients with CLL and multiple sclerosis (MS) to immunophenotype B cells and their subpopulations. Whole blood from CLL and MS patients, as well as healthy controls, was used to detect nIgM using the VH4-34 gene copy number and real-time RT-PCR. We found that the proportion of CD5+ B cells was significantly lower in MS patients than in the control group and that CD5+ B lymphocytes were significantly higher in CLL patients than in the control group. Compared to the control group, CLL patients had significantly higher levels of the VH4-34 gene copy number. On the contrary, MS patients had significantly lower VH4-34 gene copy number levels compared to the control group. As the number of antibodies in CLL patients increases due to the high number of B1 cells, we propose a new way to treat MS by extracting this natural antibody from the sera of CLL patients and injecting it into MS patients. https://ijaai.tums.ac.ir/index.php/ijaai/article/view/3620 https://ijaai.tums.ac.ir/index.php/ijaai/article/download/3620/1889