IMMUNOLOGICAL STUDIES OF GAMMA-DELTA T-CELLS IN A CASE OF LARGE GRANULAR LYMPHOCYTE (LGL) LEUKEMIA - LEUKEMIC GAMMA-DELTA+ T-CELLS ARE RESISTANT TO GROWTH-STIMULATION INVITRO BUT RESPOND TO INTERFERON-ALPHA TREATMENT INVIVO

Leukemic T cells from patient BU (WBC 22000/mul) resembled morphologically large granular lymphocytes, and expressed a Vdelta1-encoded gammadelta T-cell receptor (TCR) on their surface. Upon in vitro activation with various mitogens, IL-2-dependent Vdelta1+ cell lines were only obtained if Vdelta1+ cells had been positively selected on a cell sorter before culture. However, even under these conditions, the Vdelta1+ IL-2-dependent cell lines showed a TCR beta and gamma gene-rearrangement different from that of the freshly isolated leukemic cell population, indicating that they were not derived from the leukemic clone. Thus, known T-cell growth factors (IL-2, IL-4, IL-7) in concert with mitogenic signals failed to induce in vitro proliferation of the Vdelta1+ leukemic clone. Interestingly, the patient responded to treatment with interferon-alpha2c (daily dose of 10(6) I.U.). After 2 1/2 years of continuous interferon treatment, the patient is in partial remission with WBC around 8000/mul.