No abstract

Summary. Follicular lymphoma (FL) cells have inherited an activated hypermutation mechanism from their origin of germinal centre B cells. Based on today's knowledge of the intrinsic properties related to this mechanism and the V H base composition, reconsideration of previous reports should be made on a broader range of samples. The present study examined the mutation pattern of the V H genes expressed by 55 cases of FL. FL V H genes showed evidence of antigenic selection in 30% of cases with 88% carrying a functional sIg and 78´2% showing intraclonal variation. V H family and gene segment utilization was found to be roughly similar to that of normal B lymphocytes. FL V H genes revealed extensive variations. 17% of the V H exons harboured a total of ®ve deletions, three duplications and two insertions as compared to the most homologous germline counterpart. The V H genes of one tumour displayed three populations with varying CDR3 length at diagnosis. At relapse, emergence of a differently mutated gene, additional mutations reminiscent of ongoing mutations or no variation was prominent. From this study the heterogeneity of FLs is well established and ongoing mutations are seen in the scope of the activated status of the hypermutation mechanism rather than antigen-stimulated tumour growth.

Genetically modified dendritic cells (DC) constitute a promising approach in cancer immunotherapy. Viral gene delivery systems have been shown to be very efficient strategies, but safety concerns for their clinical use in immunotherapy remain an important issue. Recently, the technique of mRNA electroporation was described as a very efficient tool for the genetic modification of human monocyte-derived DC. Here, we show that transgene expression can be modulated by varying the amount of mRNA used for electroporation. We document that CD40 ligation leads to a significant production of IL-12 by the electroporated DC, although the level of IL-12 production is somewhat lower than for non-or mock-electroporated DC. Furthermore, we show that the electroporated DC can be frozen and thawed without loss of viability or function and that Influenza virus Matrix Protein 1 mRNA electroporated DC are capable of inducing a memory cytotoxic T lymphocyte response and are more potent in doing so than mRNA-pulsed DC. Similar results were obtained with MelanA/MART-1 mRNA electroporated DC. These results clearly indicate that mRNA-electroporated DC represent powerful candidates for use as tumor vaccines and could constitute an improvement compared with vaccines using peptide-pulsed DC.