INTERLEUKIN-12 (IL-12) ALONE OR IN SYNERGISTIC COMBINATION WITH IL-2 FOR IN-VITRO ACTIVATION OF HUMAN BONE-MARROW - DIFFERENTIAL-EFFECTS ATDIFFERENT TIME POINTS
Un. Verma et A. Mazumder, INTERLEUKIN-12 (IL-12) ALONE OR IN SYNERGISTIC COMBINATION WITH IL-2 FOR IN-VITRO ACTIVATION OF HUMAN BONE-MARROW - DIFFERENTIAL-EFFECTS ATDIFFERENT TIME POINTS, Bone marrow transplantation, 16(3), 1995, pp. 365-372
IL-12 augments many effector functions associated with T and NK cells
including induction of cytotoxic activity and secretion of various cyt
okines. In addition, synergistic responses with IL-2 in most of the fu
nctions attributed to that cytokine make IL-12 an attractive candidate
to have a potential role as an immunotherapeutic agent. We have evalu
ated the effect of rhIL-12 either alone or in combination with IL-2 on
the generation of cytotoxic effecters from normal human bone marrow,
IL-12 induced cytotoxic effecters against NK sensitive targets within
24 h of stimulation and this activity was maintained in cultures with
IL-12 supplementation for up to 2 weeks tested, The decline in NK acti
vity seen in control cultures over a period of 2 weeks was thus not ob
served in IL-12 stimulated cultures. In addition, a small increase was
also observed in cytotoxic activity against NK resistant Daudi cell t
argets, IL-12, when combined with a low to intermediate dose of IL-2,
led to enhancement in IL-2 induced cytotoxicity against both NK sensit
ive and resistant targets, However an increase in cytotoxicity against
NK resistant targets was evident only after 1 week of stimulation. Ce
llular yield and number of hematopoietic precursors (LTC-IC, CFU-GM, B
FU-e) in IL-12 stimulated cultures was comparable to or higher than co
ntrol cultures at all the three time points (days 1, 7, 14) tested. In
contrast, cultures stimulated with a combination of IL-12/IL-2 showed
an increased number of hematopoietic precursors at day 1 followed by
a marked decrease in the number of these precursors at day 7 and day 1
4. The several-fold higher levels of inhibitory cytokines such as IFN-
gamma and TNF-beta detected in these combination cultures may be respo
nsible for this biphasic behavior of hematopoietic precursors in combi
nation cultures. Thus, IL-12 has differential effects alone or in comb
ination with IL-2 on lymphoid and myeloid cells.