Discovery of CD4 Lymphocyte Regeneration Mechanisms: An Important Breakthrough for Transplant Recipients and AIDS Patients
January 11, 2009 –Published today in the prestigious journal, Nature Immunology, this study by Dr. Martin Guimond sheds light on the mechanisms that mediate CD4+ lymphocyte regeneration. This major discovery is likely to have an impact on the development of new strategies for restoring immunity in patients who undergo stem cell transplants, or who become infected with HIV.
T lymphocytes are a key component of the immune system. In order for T lymphocytes to function properly, the immune system requires two types of T lymphocytes: T CD4+ lymphocytes, which coordinate immune responses, and T CD8+ lymphocytes, which destroy infected or cancerous cells. For the majority of chemotherapy and HIV-infected patients who experience significant T lymphocyte depletion, the organ that produces these cells is unfortunately unable to restore the cell count back to a normal level. To increase the cell count, residual T lymphocytes, contained in the blood, divide in an exaggerated manner. This process is known as homeostatic proliferation, and while it regenerates T CD8+ lymphocytes, it does not regenerate T CD4+ lymphocytes, causing the cell count to remain inferior to normal levels for many years.
Dr. Guimond’s findings reveal the reasons for this phenomenon, which scientists have been researching for several years. He was able to identify a negative regulation loop in mice that restricts the ability for dendritic cells to support the homeostatic proliferation of T CD4+ lymphocytes.
“This discovery will guide us in our research as we aim to find the method that will quickly rebuild the immune systems of patients who undergo intensive chemotherapy; who receive bone marrow transplants; or who become infected with HIV,” says Dr. Guimond.
Dr. Guimond joined the Immunology-Oncology Research Unit in early September 2008 to conduct studies on cellular therapy. His research lends itself perfectly to the mission of the Center of Excellence in Cellular Therapy, due to open in 2010.
An article about Dr. Guimond’s discovery was published in La Presse and on Radio-Canada’s website. Dr. Guimond also gave an interview to Robert Dutrizac at 98,5FM, and to Simon Durivage at RDI.
About the Study
The study, entitled "Interleukin 7 Signaling in Dendritic Cells Regulates the Homeostatic Proliferation and Niche Size of CD4+ T Cells,” is the work of Dr. Guimond in collaboration with a number of American investigators: Drs. Rachelle G Veenstra, David J Grindler, Hua Zhang, Yongzhi Cui, Ryan D Murphy, Su Young Kim, Risu Na, Lothar Hennighausen, Sema Kurtulus, Batu Erman, Polly Matzinger, Melinda S Merchant & Crystal L Mackall.