Lack of in vitro colony (CFUC) formation and myelosuppressive activity in patients with severe aplastic anemia after autologous hematologic reconstitution.

In vitro colony formation (CFUC) was studied in 8 patients with severe aplastic anemia (SAA) in complete hematologic remission following high dose pulse methylprednisolone (P/6-MPr) and/or antilymphocyte globulin (ALG). All patients except one were off maintenance treatment at the time of study, and follow-up ranged from 271 to 630 days. All patients showed marked reduction of colonies (2 +/- 3/2.5 x 10(5) cells; our normal 61 +/- 14) and clusters (77 +/- 45; our normal 179 +/- 83), which persisted for as long as 600 days after initial therapy. Incubation of patients' marrow with ALG did not enhance significantly colony formation. Co-culture of bone marrow from 6 patients with SAA in remission and normal marrow produced a marked inhibition of the expected colonies (84 +/- 16%) and clusters (29 +/- 23%). Incubation of patients' marrow with ALG prior to the co-culture experiments did not prevent suppression of colonies and clusters. Co-culture of patients' peripheral blood lymphocytes with normal marrow had no effect on colony formation. Therefore remission marrow from patients with SAA exhibits severely impaired in vitro growth (CFUC) and marked myelosuppressive activity against normal marrow cells. Incubation of patients' marrow with ALG has no significant effect on either assay.