October 10, 2002
Dr. Timothy Schacker, associate professor of medicine and author of the study, and colleagues removed up to four lymph nodes from each of 11 HIV-positive patients over a six-month period and examined them for damage. They found that in some patients, inflammatory cells sent in by the body to help fight HIV inadvertently caused damage to the lymph tissue. This damage, in turn, triggered the formation of scar tissue, which prevented CD4 T-cells from replicating in the lymph nodes.
Doctors measure the effectiveness of drug therapies by the amount of virus found in the blood and by the number of CD4 T-cells found in the lymph nodes. The goal is to eliminate the virus from the blood and boost the CD4 T-cell count to strengthen the immune system. Yet studies show that about 25 percent of patients who have no HIV in their blood following drug treatment do not experience a corresponding improvement in their CD4 T-cell count, Schacker said. CD4 T-cells live and multiply in lymph nodes but are frequently sent out in the blood to fight off bacterial and viral invaders. But HIV invades the lymph nodes and relentlessly attacks the CD4 T-cells.
The study showed that the amount of damage in the lymph nodes is directly related to the size of the CD4 T-cell population: the higher the damage, the lower the CD4 T-cell count. Schacker said he and his colleagues now want to expand the study to about 30 patients and see if the discovery has clinical applications. "We think it has uncovered an important feature in how the virus works," he said.