Phenotype, function, and in vivo migration and survival of allogeneic dendritic cell progenitors genetically engineered to express TGF-beta

Background. Administration of donor bone marrow (BM)-derived dendritic cell (DC) progenitors (DCp) that are major histocompatibility complex (MHC) cla ss II+ but costimulatory molecule (CD40, CD80, CD86)-deficient can prolong mouse heart allograft survival. This is associated with microchimerism and inhibition of antidonor cytotoxic T lymphocyte (CTL) activity. Genetic modi fication of these donor antigen-presenting cells to express an immunosuppre ssive molecule(s) may enhance their in vivo survival and potential toleroge nicity. Methods. The surface phenotype of B10 (R-2(b)) DCp before and after gene tr ansfer using replication-deficient. adenoviral (Ad) vectors was determined by monoclonal antibody (mAb) staining and now cytometry. Transforming growt h factor-beta (TGF-beta) production was quantitated by enzyme-linked immuno sorbent assay. Allostimulatory activity of the gene-transduced DCp was asce rtained by mixed leukocyte reaction (MLR) and CTL induction. To assess thei r in vivo migratory activity and survival, the transduced cells were inject ed subcutaneously into one hind footpad of C3H (H-2(k)) mice. Tissues (drai ning popliteal lymph nodes [LN], spleens, and thymi) were removed 1, 2, 7, and 14 days later and stained for donor MHC class II using anti-IA(b) mAb i n an immunohistochemical procedure. The mean number of IA(b+) cells per uni t area was determined. Results. Transduction with a control Ad vector (Ad-LacZ) at 50 multiplicity of infection slightly increased CD40 and CD86 expression and up-regulated the poor allostimulatory activity of the DCp assessed by MLR and CTL respon ses. These effects on function were negated in Ad-TGF-beta 1-transduced cel ls. After their injection into mouse footpads, the gene-transduced IA(b+) c ells were observed in maximal numbers in the popliteal LN at day 1 and in m arginal zones and T-dependent areas of spleens (peak at day 7) but were rar e in thymi. Transduction with Ad-LacZ reduced the numbers of IA(b+) cells i dentified in both LN and spleens at all time points postinjection, suggesti ng that the vector alone affected DC life span in allogeneic recipients. TG F-beta 1 transgene expression not only fully prevented the reduction in DC induced by Ad transduction alone, but also increased numbers and prolonged the survival of donor cells in the spleen, as shown by a two- to fivefold i ncrease in IA(b+) cells at days 2 14 compared with control (Ad-LacZ-transdu ced) DC. Conclusion. BM-derived DCp can be transduced efficiently to express TGF-bet a 1 using an Ad vector. They exhibit very poor allostimulatory activity and similar migration characteristics in vivo to unmodified DCp. Survival of T GF-beta gene-transduced DC, however, is enhanced significantly compared wit h unmodified and (especially) control Ad-LacZ gene-transduced DC. Genetic e ngineering of donor DC to express the immunosuppressive-molecule TGF-beta p romotes their survival in allogeneic hosts and may potentiate their previou sly reported tolerogenicity.