DCs are obtained in vitro through monocyte differentiation, previous studies show the maturation of DCs by live BCG, but for models targeting immunosuppressed patients, the maturation of DCs by dead BCG needs to be investigated. In this work we evaluated the phenotypic and functional characteristics of human DCs in vitro stimulated by dead BCG.

DCs were obtained from the isolation of monocytes from the blood of healthy donors. After the isolation step, monocytes were cultured with IL-4 and GM-CSF for differentiation into immature DCs. For terminal maturation, TNF-α and IFN-α (DC-TNF) or killed BCG (DC-BCG) were added. After maturation, DC-TNF and DC-BCG were co-cultured for 5 days with autologous and allogeneic lymphocytes previously stained with CFSE fluorochrome. To phenotypically characterize DCs, after their terminal maturation, some markers were investigated. The strain used was the lyophilized Moreau-RJ.

DC-TNF and DC-BCG cultures showed rates of cells expressing HLA-DR: 98% and 98%; CD1A: 69% and 72.37%, CD86: 97% and 98%,CD80: 39% and 36%, CD40: 21% and 15%, PD-1: 18% and 14% and CD83: 55% and 47%, respectively. There was a significant difference in the expression of percentage values only for CD80. MFI (mean fluorescence intensity) levels in DC-TNF and DC-BCG were high in HLA-DR: 9251 and 6867, in CD86: 12975 and 10772, and in CD1A: 6242 and 5694, respectively. DC-TNF and DC-BCG had MFI for PD-1: 755 and 1156; CD40: 877 and 745, in CD80: 753 and 598, and in CD83: 624 and 1529, respectively. There was a significant difference in HLA-DR MFI levels. In lymphocyte proliferation DC-BCG showed greater proliferation of autologous lymphocytes: 11% and 21% allogeneic, while DC-TNF cells: 5% autologous and 16% allogeneic.

The use of dead BCG promotes the maturation of DCs at levels equivalent to TNF. But BCG potentiates lymphocyte proliferation at a higher rate. To interpret the results obtained, a study of cytokine production will be performed.