Expression of Ig genes. Regulation of transcription and production of human antibodies

Abstract: During B lymphocyte development, the transcriptional activity of the IgH locus is subject to spatial and temporal changes. The 3' enhancer (3'E) has been suggested to play an important role in regulation of immunoglobulin gene expression late in B cell development. We have investigated, using transgenic mice, the role of the 3'E in regulating Ig gene expression. Mice harbouring a rearranged IgH gene potentiated by the VH promoter in combination with the IgH intron enhancer (µE), the 3'E or the µE/3'E pair were generated. The 3'E activity is mainly observed in lymphoid tissues and is mainly restricted to the in vivo activated B cells. The 3'E can potentiate Ig gene expression directly in conjunction with the VH promoter. The expression level of the µE/3'E controlled transgene is fivefold higher as compared to the transgene controlled by the µE alone. The aim of my subsequent studies has been to generate and produce human monoclonal antibodies. We have focused our interest on immortalization of the variable region genes, from hybridoma or from a single antigen-specific B cell, using the powerful PCR technique. The variable region genes from single B cells can be immortalized directly or after a cellular amplification step, involving the EL-4 and CD40 cell culture systems. The variable region genes obtained can thereafter be expressed either as Ab fragments, in prokaryotic host cells, or as the entire Ab, in eukaryotic host cells. To allow efficient expression of intact Ab we have optimized a eukaryotic IgH gene expression vector using different combinations of regulatory elements.