Synergism of interleukin-12 and interleukin-3 on development of hematopoietic progenitors

Interleukin-12 induces IFN-γ secretion and STAT signaling implying its potential regulation of Th1 cell response in Nile tilapia

As a pleiotropic cytokine consisting of IL-12p35 and IL-12p40, Interleukin-12 (IL-12) features in inflammation regulation and anti-bacterial immunity. While IL-12 homologs have been identified in non-mammalian species, the precise mechanisms by which IL-12 contributes to early adaptive immune responses in vertebrates remain incompletely understood. Herein, an evolutionary conserved Oreochromis niloticus IL-12 (defined as OnIL-12) was identified by synteny characterization, structural comparisons and phylogenetic pattern of IL-12p35b and IL-12p40a. IL-12p35b and IL-12p40a exhibited widespread expression in lymphoid-related tissues of tilapia, while their mRNA expression in head-kidney demonstrated a significant increase after Edwardsiella piscicida infection. Compared with other lymphocytes, recombinant OnIL-12 (rOnIL-12) displayed stronger affinity binding to T cells. Although stimulation of lymphocytes with the p35b or p40a subunit resulted in a significant induction of IFN-γ expression, rOnIL-12 showed stronger potential to promote IFN-γ expression than these subunits. rOnIL-12 not only elevated the mRNA expression level Th1 cell-associated transcription factor T-bet in lymphocytes, but also increased the proportion of CD4-1+IFN-γ+ lymphocytes. Moreover, the mRNA and phosphorylation levels of STAT1, STAT3, STAT4 and STAT5 were enhanced by rOnIL-12. These findings will offer previous evidence for further exploration into the regulatory mechanisms of Th1 cellular immunity in early vertebrates.

A Review of Clinical and Preclinical Studies on Therapeutic Strategies Using Interleukin-12 in Cancer Therapy and the Protective Role of Interleukin-12 in Hematological Recovery in Chemoradiotherapy

Interleukin-12 (IL-12), a heterodimeric glycoprotein with α and β subunits covalently bonded with a disulfide bond, is a potent anticancer agent. Its action is accomplished through a linkage of the adaptive and innate immune responses. IL-12 can promote the recovery of the hematopoietic system after cancer chemoradiotherapy by stimulating the physiological processes of stem cells, including cell proliferation and differentiation, reconstitution of hematopoietic function, and peripheral blood count recovery. We review therapeutic strategies using IL-12 in clinical studies, including single-agent and combination strategies in hematological tumors and solid tumors, and studies on the protective effects of IL-12 in chemoradiotherapy. This review highlights promising therapeutic strategies based on the anticancer role of IL-12 and the potential protective effects of IL-12 for cancer patients receiving chemoradiotherapy.

In vitro and in vivo responses to interleukin 12 are maintained until the late SIV infection stage but lost during AIDS

The in vitro proliferative responses of macaque peripheral blood mononuclear cells (PBMCs) to IL-12 appeared similar before and early after SIV infection, whereas macaque PBMCs sampled during symptomatic stages of SIV infection showed markedly decreased responses. IL-12 was administered to SIVmac239-infected rhesus macaques either during the asymptomatic or the AIDS stage of infection in efforts to evaluate the effect of this cytokine on immune responses, viral loads, and hematopoietic functions in vivo. IFN-gamma secretion levels induced during the asymptomatic or early symptomatic phase were similar to preinfection induced levels, whereas in later AIDS stages this response was lost. The constitutive levels of other measured cytokines were not affected by IL-12 administration in vivo. The frequency and activity of circulating NK cells were markedly enhanced at early stages but not at symptomatic stages of SIV infection. pCTL frequencies were enhanced at early symptomatic stages but not at late AIDS stages. Despite its immunomodulatory effect, IL-12 did not seem to exacerbate or inhibit the replication of SIV in vivo, or the frequency of circulating infected lymphocytes. IL-12 administration was associated with a significant yet subclinical and transient decrease in hematocrit and hemoglobin levels without evidence of hemolysis, hemodilution, or reduction in the frequency of colony-forming unit potential of bone marrow CD34+ cells. This phenomenon may be explained by a functional inhibition of differentiation rather than an altered generation of bone marrow precursors. Thus, these results suggest that IL-12 may benefit HIV-1-infected patients only as long as their immune system retains its capability to respond to cytokine stimulation.

IL-12 indirectly enhances proliferation of 5-FU-treated human hematopoietic peripheral blood CD34+ cells

Interleukin-12 (IL-12) or natural killer cell stimulatory factor (NKSF), has multiple effects on T lymphocytes and natural killer cells. In this study, the effect of IL-12 on human hematopoiesis was studied by analyzing the growth of CD34+ peripheral blood stem cells (PBSC), in steady state. In the presence of Epo, IL-12 alone or in combination with IL-3 or SCF had no effect on the formation of colonies from CD34+ cells. In culture with Epo, G-CSF, and IL-3, the effect of Flt3-ligand (FL) on CD34+ PBSC was investigated in the presence or absence of IL-12. No additional effect of IL-12 was observed when combined with FL. We evaluated 5-FU-treated human CD34+ PBSC proliferation in cultures with Epo, G-CSF, and IL-3, in the presence or absence of IL-12. No cytokine combination enhanced colony formation from 5-FU-treated CD34+ cells. However, in cultures of 5-FU-treated human CD34+ cells, the most efficient combination was IL-3 + Epo + G-CSF + Accessory cells (CD34-). Furthermore, IL-12 enhanced this colony formation significantly. To investigate whether immature CD34+ cells were responsible for FL or SCF, 5-FU-treated human CD34+ cells were cultured with or without IL-12. Whereas no synergistic effect was observed in combination with IL-12, SCF alone significantly enhanced colony formation. However, the colony number was found to be smaller than with the potent combination of accessory cells in the presence of IL-12. These results indicate that accessory cells, lost in CD34+ cell purification, could be partly responsible for an IL-12 effect on immature human PBSC proliferation.

Growth factors and hematopoietic stem cells

The hematopoietic system is mediated in part by cell-to-cell interactions and soluble mediators or growth factors (cytokines). A large number of cytokines directly and potently control hematopoietic stem and precursor cell proliferation and differentiation. This review focuses on the recent studies devoted to the role of cytokines in the ex vivo expansion and differentiation of hematopoietic stem and precursor cells.