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Dennis W. Ross, MD, PhD; Gene P. Siegal, MD, PhD
JAMA. 1990;263(19):2671-2672. doi:10.1001/jama.1990.03440190127068.
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In keeping with the inevitable wave of changes experienced by medicine each year, several developing technologies in the field of pathology are particularly noteworthy.

In hematopathology, recombinant DNA technology has provided a tool that increases our understanding of disease and enhances diagnostic capabilities. The rearrangement of the immunoglobulin genes and T-cell receptor genes by differentiating lymphocytes reveals an intricate process that is helping us understand neoplasia.1 Early hematopoietic progenitor cells begin lymphoid differentiation by rearranging the δ-chain gene of the T-cell receptor. If this rearrangement produces a DNA sequence without a triplet stop codon for termination of transcription through the gene (a so-called open reading frame), the cell will bear γ/δ-chain dimers and become a CD3+ CD4- CD8- natural killer/cytotoxic lymphocyte. δ-Chain rearrangement usually fails; then the lymphocyte attempts an α-chain rearrangement. The α-chain gene surrounds the δ-chain DNA sequences and an α-chain rearrangement results in permanent deletion of


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