Natural killer cells suppress human erythroid stem cell proliferation in vitro

Abstract

To determine the role of natural killer (NK) cells in the regulation of human erythropoiesis, we studied the effects of NK-enriched cell populations on the in vitro proliferation of erythroid stem cells at three different levels of maturation (day 14 blood BFU-E, day 5–6 marrow CFU-E, and day 10–12 marrow BFU-E). NK cells were enriched from blood by Percoll density gradient centrifugation and by fluorescence- activated cell sorting (FACS), using the human natural killer cell monoclonal antibody, HNK-1. The isolated enriched fractions were cocultured with autologous nonadherent marrow cells or blood null cells and erythropoietin in a methylcellulose erythroid culture system. Cells from low-density Percoll fractions (NK-enriched cells) were predominantly large granular lymphocytes with cytotoxic activity against K562 targets 6–10-fold greater than cells obtained from high- density Percoll fractions (NK-depleted cells). In coculture with marrow nonadherent cells (NA) at NK:NA ratios of 2:1, NK-enriched cells suppressed day 5–6 CFU-E to 62% (p less than 0.025) of controls, whereas NK-depleted cells slightly augmented CFU-E to 130% of controls (p greater than 0.05). In contrast, no suppression of day 10–12 marrow BFU-E was observed employing NK-enriched cells. The NK CFU-E suppressor effects were abolished by complement-mediated lysis of NK-enriched cells with the natural killer cell antibody, HNK-1. Highly purified HNK- 1+ cells separated by FACS suppressed marrow CFU-E to 34% (p less than 0.025) and marrow BFU-E to 41% (p less than 0.025) of controls. HNK- cells had no significant effect on either BFU-E or CFU-E growth. NK- enriched cells were poor stimulators of day 14 blood BFU-E in comparison to equal numbers of NK-depleted cells or T cells isolated by E-rosetting (p less than 0.01). Interferon boosting of NK-enriched cells abolished their suboptimal burst-promoting effects and augmented their CFU-E suppressor effects. These studies provide evidence for a potential regulatory role of NK cells in erythropoiesis. The NK suppressor effect is maximal at the level of the mature erythroid stem cell CFU-E. These findings may explain some hypoproliferative anemias that develop in certain NK cell-activated states.

Inhibition of bone marrow colony formation by human natural killer cells and by natural killer cell-derived colony-inhibiting activity.

“…Our results from experiments using purified lymphocyte preparations show that inhibition with identical specificity is obtained when B73.1 + NK cells are incubated with bone marrow cells. These data confirm and extend previous reports showing that cell preparations enriched for NK cells on the basis of their physical properties (density) (9) or surface phenotype (e.g., HNK-1 + cells [15], FcR + [11,16,18], E-rosetting and -nonrosetting cells [13,14]) suppress CFU-E, BFU-E, and CFU-GM bone marrow colonies. We now report that proliferation and differentiation of muitipotent CFU-GEMM precursor cells are also efficiently inhibited by NK cells.…”

“…Alternatively, different CSF preparations may drive myeloid differentiation differently and thus the difference in results may only be superficial. The inability of NK cells to suppress BFU-E colonies is consistent with findings in other studies (15,16), which have all shown that this type of colony is much more resistant to the inhibitory effect of NK cells than are CFU-E or CFU-GM. In our experiments, the number of precursor cells present in the PBL preparations added to the bone marrow cells was not sufficient to affect the measured extent of inhibition, due to the low PBL-to-bone marrow cell ratio used.…”

Peripheral blood lymphocyte subpopulations in patients with primary proliferative and secondary polycythaemia.

“…The helper Tcells, with the cooperation of monocytes, stimulate progenitor cell growth, whereas the suppressor cells inhibit growth of these cells. '0 - 13 Zoumbos et al"4 reported that 10 of 12 patients with aplastic anaemia had increased numbers of activated suppressor Tcells compared with the numbers in control subjects. Furthermore, these cells were found to be releasing y-interferon, which suppressed progenitor cell growth in vitro.…”

Acquired pure red cell aplasia: unraveling the immune pathogenesis

“…NK cells from an aPRCA patient were observed to suppress the growth of BFU-E and CFU-E and exhibit MHCunrestricted cytotoxicity against K562 (a human erythroblastic leukemia cell line). [79,[82][83][84] The clonal proliferation of LGLs associated with aPRCA does not always involve neoplastic monoclonal expansions. A portion of these cases represent a series of physiologic polyclonal responses to an unknown antigen on EPs.…”