OUTLINE: This is a dose escalation study of stem cell factor (SCF). Patients receive filgrastim (G-CSF) subcutaneously (SC) followed by SCF SC daily for 7-10 days. Beginning on the fifth day of G-CSF and SCF injections, peripheral blood stem cells (PBSC) are collected over several days. PBSC are later reinfused and patients receive G-CSF SC daily until hematopoietic recovery. At least 30 days but no later than 110 days following transplant, patients who did not experience adverse reactions to SCF during mobilization begin posttransplant immunotherapy. Patients receive interleukin-2 SC daily and SCF SC 3 times weekly for 6 weeks. Treatment continues in the absence of unacceptable toxicity or disease progression. Cohorts of 3-6 patients receive escalating doses of SCF during posttransplant immunotherapy until the maximum tolerated dose (MTD) is determined. The MTD is defined as the dose preceding that at which 2 of 3 or 2 of 6 patients experience dose limiting toxicities. Patients are followed at 1 week, every 3 months for 1 year, and then every 6 months thereafter.