Differential effects of IL-2 incubation on hematopoietic potential of autologous bone marrow and mobilized PBSC from patients with hematologic malignancies

Culturing of hematopoietic progenitor cells for 24 h with IL-2 generates cy totoxic effector cells that mediate in vitro and possibly in vivo antitumor activity. We examined the effect of IL-2 incubation on progenitor cells fr om 24 patients with hematologic malignancies using paired autologous bone m arrow (ABM) and PBSC to determine differences in hematopoietic potential. C ells were cryopreserved and stored in liquid nitrogen until conditioning th erapy was completed. After thawing, cells were incubated with IL-2 for 24 h at 37 degrees C. Paired samples of ABM and PBSC from the same patient were analyzed for nucleated and mononuclear cell number, CD34 antigen expressio n, and colony-forming unit (CFU) activity before and after IL-2 incubation. There was a significant decrease in the average number of mononuclear cell s (MNC) (x10(8)/kg) (<0.001) and CD34(+) cells (x 10(6)/kg) (0.006) from bo th AEM and PBSC after 24 h IL-2 culture (ABM MNC: 0.6 +/- 0.1 vs. 0.4 +/- 0 .0, p = < 0.001; PBSC MNC: 4.4 +/- 0.5 vs. 3.7 +/- 0.4, p = 0.03; ABM CD34( +): 2.4 +/- 0.5 vs. 1.3 +/- 0.3, p = < 0.001; PBSC CD34+: 6.6 +/- 1.8 vs. 5 .0 +/- 1.2, p = 0.05). However, whereas ABM CFU/10(5) MNC plated (269.3 +/- 47.2 vs. 385.6 +/- 70.6) were significantly increased (p = 0.005), there w as no change in PBSC CFU (271.0 +/- 47.2 vs. 257.3 +/- 48.5). The mean plat ing efficiency (%) of ABM CD34(+) cells was markedly increased after IL-2 i ncubation (10.1 +/- 3.3 vs. 19.0 +/- 7.2, p = 0.04), although it was lower than that of PBSC CD34(+) cells, which did not change significantly in cult ure (29.4 +/- 5.5 vs. 36.0 +/- 6.5). Additional work is in progress to dete rmine the cause and significance of the enhanced plating efficiency of the ABM progenitor cells.