Identification and isolation of Ag-specific T cells by flow sorting.

Abstract

Stem-cell grafts in combination with ablative chemo/ radiotherapy offer a potential cure for hematological malignancies refractory to more conventional therapy. However, HLA-identical donors are available to only 25% of the population, and alternative donor sources must be considered to improve the accessibility of transplantation. For example, partially mismatched related donors are available for 95% of patients requiring a transplant. However, HLA disparities between donor and recipient require that partially mismatched grafts undergo T-cell depletion in order to remove T cells that would otherwise cause potentially fatal GvHD. Since T-cell depletion strategies currently rely upon non-selective methodologies, transplant recipients therefore remain grossly immunocompromised for extended periods of time posttransplant. Thus, although T-cell depletion makes transplants more accessible, it is associated with a greatly increased risk of opportunistic and potentially lethal viral and fungal infections, and with a higher incidence of leukemic relapse. CMV reactivation after partially mismatched related donor BMT, when the host is seriously immunocompromised, is a cause of severe morbidity and even mortality. Current drug therapies are not satisfactory and may give rise to significant myelosuppression, drug resistance and other side effects. Immunotherapy may be preferable to drug therapy and may contribute to preventing CMVrelated illnesses in BMT recipients. The ex vivo generation of T cells that can confer highly specific immunity against defined pathogenic targets and their incorporation into BM grafts or their infusion post-transplant has become the focus of many research groups.