Dr. Rita Effros' research is focused on the immune deficiency associated with aging and HIV/AIDS, with particular emphasis on a novel aspect of T-cell biology known as replicative senescence.

Replicative senescence describes the irreversible state of growth arrest which all normal human somatic cells reach after a finite number of cell divisions. Using a novel cell culture system established in her laboratory, Effros and her colleagues have defined certain characteristics of replicative senescence in CD8 T-lymphocytes. These include the inability to undergo further cell division, loss of expression of the CD8 costimulatory molecule, telomere lengths which shorten to 5 - 7 kb from an initial 10 - 11 kb length, loss of the ability to upregulate telomerase, altered cytokine profiles and resistance to apoptosis. Her research has shown that T-cells with these identical characteristics accumulate in the elderly and may explain the dramatic age-associated immune decline, manifested by higher cancer incidence and increased infections. Moreover, Effros has shown that certain CD8+ T-cells in HIV-infected subjects exhibit all the characteristics of replicative senescence and that these "useless" T-cells accumulate with disease progression. Thus, CD8 T-cell replicative senescence is a newly defined aspect of AIDS pathogenesis, which may explain the increased lymphoma incidence as well as the diminished capacity to control both the HIV itself and opportunistic pathogens.

Current work in her lab focuses on genetic and non-genetic strategies to enhance telomerase activity in human T-cells. In addition, ongoing studies are addressing the mechanistic link between chronic T-cell activation leading to replicative senescence and loss of bone mass in the context of aging and HIV disease.