Bone marrow cells promote TH2 polarization and inhibit virus-specific CTL generation

This laboratory recently reported that human bone marrow cells (BMC) inhibit the generation of virus-specific CTL in culture. The culture supernatants contained increased levels of prostaglandin E(2) (PGE(2)) (shown to favor TH2 cell development) and also inhibited EBV-CTL effector cell development. In this study, we obtained PBL from Epstein-Barr virus (EBV) IgG antibody positive kidney transplant recipients (R) and their living-related donors (LRD) one year after renal transplantation. EBV-specific CTL were then generated in vitro by stimulating PBL with autologous EBV-transformed B cells (EBV-B) in the presence or absence of autologous BMC. The addition of BMC to the EBV-CTL generation cultures increased the intracellular expression in CD3+ cells of IL-4,-5,-6,-10, and -13. These CD3+ cells also expressed increased levels of the TH2 associated receptor CCR3. Inhibition was even observed by preparing EBV-CTL generating cultures in trans-wells that separated the autologous BMC from the PBL + EBV-B. It was then observed that CD3+ cells obtained after 7 days of culture in the presence of autologous BMC could be used as inhibitors of EBV-CTL generation. Protein Kinase A (PKA), a cAMP kinase that is involved in the upregulation of TH2 cytokine activity, was increased in EBV-CTL cultures by the presence of BMC. Additionally, IL-4-mediated signal transduction and activation of transcription (STAT-6) phosphorylation was slightly increased. These results show that the BMC inhibition is mediated by soluble factors (cytokines) and that cell-cell contact in this autologous system is not required, so that BMC (at least partially, via cytokine production) promote TH2 polarization in culture. Moreover, TH2 cells induced by culturing with autologous BMC directly inhibit EBV-CTL generation, and TH2 associated PKA, CCR3, and STAT-6 phosphorylation are enhanced by BMC.