Evidence for progenitors of chronic lymphocytic leukemia B cells that undergo intraclonal differentiation and diversification.
Peripheral blood mononuclear cells from five patients with IgG+ B-type chronic lymphocytic leukemia (B-CLL) were analyzed for the presence of clone-specific Ig H chain variable region gene mRNA transcripts linked to C mu and/or C alpha. This was assessed by (1) comparing the lengths of portions of the VHDJH of the IgG+ CLL clones with those of the mu and alpha isotype-expressing B cells, (2) performing clone-specific endonuclease digestion studies, and (3) determining the DNA sequences of the mu and alpha isotype-expressing cDNA. Thus, when B-cell mRNA from these five patients were reverse transcribed with C gamma-specific primers and then amplified by polymerase chain reaction, dominant cDNA were found with lengths corresponding to those of the IgG+ CLL B cell. In addition, in four cases, cDNA of lengths identical to those of the CLL B cell were detected when mRNA was reverse transcribed and amplified using c mu- and/or C alpha-specific primers, strongly suggesting clonal relatedness. These CLL-related mu- and alpha-expressing cDNA were present in greater amounts that unrelated (non-CLL) mu- and alpha-expressing cDNA from normal B cells that used genes of the same VH family. When the sequences of these CLL-related C mu- and C alpha-expressing cDNA were compared with those of the IgG+ CLL clones, it was clear that they were derived from the same ancestral gene as the IgG-expressing CLL B cell, thus documenting their common origin. Finally, nucleotide point mutations were observed in the mu- and alpha-expressing cDNA of certain patients, indicating divergence with the CLL. These data suggest that IgM+ B cells, which are precursors of the leukemic B cells, exist in increased numbers in the blood of most patients with IgG+ B-CELL and that these cells may differentiate, accumulate V genes mutations, and undergo isotype switching in vivo. In addition, the data are consistent with a sequential-hit model for the evolution of CLL.
Dono
M
M
Department of Medicine, North Shore University Hospital, Manhasset, NY 11030, USA.
Hashimoto
S
S
Fais
F
F
Trejo
V
V
Allen
S L
SL
Lichtman
S M
SM
Schulman
P
P
Vinciguerra
V P
VP
Sellars
B
B
Gregersen
P K
PK
Ferrarini
M
M
Chiorazzi
N
N
D001483:Base Sequence; D002454:Cell Differentiation; D002999:Clone Cells; D017931:DNA Primers / Q000737:chemistry; D015322:Gene Rearrangement, B-Lymphocyte; D005803:Genes, Immunoglobulin; D006801:Humans; D007137:Immunoglobulin alpha-Chains / Q000235:genetics; D007148:Immunoglobulin mu-Chains / Q000235:genetics; D015451:Leukemia, Lymphocytic, Chronic, B-Cell / Q000473:pathology*; D008969:Molecular Sequence Data; D012333:RNA, Messenger / Q000235:genetics; D016415:Sequence Alignment; D012689:Sequence Homology, Nucleic Acid; D014158:Transcription, Genetic
D017931:DNA Primers; D007137:Immunoglobulin alpha-Chains; D007148:Immunoglobulin mu-Chains; D012333:RNA, Messenger