Variable region gene analysis of an isotype-switched (IgA) variant of chronic lymphocytic leukemia.
Chronic lymphocytic leukemia of B-cell origin (B-CLL) is generally thought to arise by neoplastic transformation of B lymphocytes, which express CD5 and have features of an early stage of B-cell differentiation. To study isotype-switched B-CLL as a potentially more differentiated variant, we performed genetic and functional immunoglobulin (Ig) gene analysis in two cases of CD5+ B-CLL in which the peripheral blood mononuclear cells (PBMC) secreted predominantly IgA (CLL-249) or IgG (CLL-412) when stimulated with pokeweed mitogen in vitro. By cDNA sequencing and by studies of CLL-heterohybridomas, CLL-249 expresses the heavy chain constant region C alpha as anticipated, while CLL-412 expresses C mu, not C gamma. In CLL-249, the expressed VH gene is 98% homologous to VH26, a germline VH3 gene that occurs frequently in the fetal repertoire, and which has been associated with anti-DNA specificity. The VL gene of CLL-249 is a lambda VL gene for which the germline sequence is not known. In CLL-412, the VH gene is 100% homologous to the VH1 gene of a published anti-DNA antibody (21/28), and is probably a germline gene sequence; the VL gene is 100% homologous to 15AVKI, also a germline gene. The supernatant antibody of the CLL-412 heterohybridoma is an IgM-kappa, which reacts with ssDNA and cardiolipin. The CLL-249 heterohybridoma secreted IgA-lambda, which bound none of the antigens tested, a finding that may be related to amino acid differences from the probable germline V genes. The demonstration of an in vivo isotype-switched variant, such as CLL-249, suggests that B-CLL may be a heterogeneous group of clonal disorders, of which less common variants may have features of more differentiated B-cell stages, such as isotype switching.
Friedman
D F
DF
Department of Pathology and Laboratory Medicine, Hospital of the University of Pennsylvania, Philadelphia 19104.
Moore
J S
JS
Erikson
J
J
Manz
J
J
Goldman
J
J
Nowell
P C
PC
Silberstein
L E
LE
D000595:Amino Acid Sequence; D001483:Base Sequence; D015139:Blotting, Southern; D002308:Cardiolipins / Q000276:immunology; D003001:Cloning, Molecular; D004273:DNA, Neoplasm / Q000097:blood / Q000235:genetics / Q000302:isolation & purification; D004797:Enzyme-Linked Immunosorbent Assay; D005803:Genes, Immunoglobulin; D014644:Genetic Variation; D006801:Humans; D006825:Hybridomas / Q000276:immunology; D007070:Immunoglobulin A / Q000235:genetics* / Q000302:isolation & purification; D007143:Immunoglobulin Heavy Chains / Q000235:genetics; D007135:Immunoglobulin Variable Region / Q000235:genetics*; D015451:Leukemia, Lymphocytic, Chronic, B-Cell / Q000235:genetics* / Q000276:immunology*; D008969:Molecular Sequence Data; D009000:Monocytes / Q000502:physiology; D009838:Oligodeoxyribonucleotides
D002308:Cardiolipins; D004273:DNA, Neoplasm; D007070:Immunoglobulin A; D007143:Immunoglobulin Heavy Chains; D007135:Immunoglobulin Variable Region; D009838:Oligodeoxyribonucleotides