title: Molecular characterization of a supratypic cross-reactive idiotype associated with IgM autoantibodies.
abstract: Neoplastic B cells from patients with chronic lymphocytic leukemia (CLL) or small lymphocytic lymphomas (SLL) frequently express surface Ig reactive with the mouse mAb, Lc1. Raised against a human monoclonal IgM with rheumatoid factor activity, Lc1 detects a major cross-reactive Id (CRI) present on the H chain of many monoclonal IgM autoantibodies. In contrast to other major autoantibody-CRI investigated to date, we note that the Lc1-CRI is expressed by subpopulation of cells in the germinal centers, as well as in the mantle zones, of secondary human B cell follicles. To examine the molecular basis for Lc1 expression, we used the polymerase chain reaction to isolate the functionally rearranged Ig VH genes of monoclonal Lc1-reactive B cell populations from six unrelated patients with CLL or SLL. Although the neoplastic B cells from most patients with CLL or SLL express the CD5 surface differentiation Ag, the lymphoma cells from one patient with SLL were CD5-negative. We find that the Lc1-reactive cells from each cell population have Ig rearrangements involving a VH gene of the VH4 subgroup. However, the VH4 genes rearranged in different Lc1-reactive tumor populations may originate from at least two disparate germ-line VH4 genes. Also, in contrast to the CD5-positive tumor populations, we find evidence for intraclonal diversity in the functionally rearranged VH4 genes of the CD5-negative SLL. Collectively, this study discerns a degeneracy in the VH4 genes that can encode the Lc1 CRI, indicating the term "supratypic cross-reactive idiotype" may best describe the specificity of the Lc1 mAb. Also, this study suggests that expression of CD5 may delineate categories of B cell SLL that differ in their relative rates of constitutive Ig V gene somatic mutation.
authors.affiliation: Sam and Rose Stein Institute for Research on Aging, Department of Medicine, University of California, San Diego, La Jolla 92093-0945.
authors.forename: L F
authors.initials: LF
authors.lastname: Pratt
authors.forename: R
authors.initials: R
authors.lastname: Szubin
authors.forename: D A
authors.initials: DA
authors.lastname: Carson
authors.forename: T J
authors.initials: TJ
authors.lastname: Kipps
mesh_terms: D000595:Amino Acid Sequence; D000888:Antibodies, Anti-Idiotypic / Q000276:immunology*; D001323:Autoantibodies / Q000276:immunology*; D001483:Base Sequence; D003429:Cross Reactions; D015326:Gene Rearrangement, B-Lymphocyte, Heavy Chain; D005803:Genes, Immunoglobulin; D006801:Humans; D007130:Immunoglobulin Idiotypes / Q000276:immunology*; D007075:Immunoglobulin M / Q000276:immunology*; D007135:Immunoglobulin Variable Region / Q000235:genetics; D015448:Leukemia, B-Cell / Q000235:genetics; D008969:Molecular Sequence Data; D009841:Oligonucleotides / Q000737:chemistry; D016133:Polymerase Chain Reaction
chemical_list: D000888:Antibodies, Anti-Idiotypic; D001323:Autoantibodies; D007130:Immunoglobulin Idiotypes; D007075:Immunoglobulin M; D007135:Immunoglobulin Variable Region; D009841:Oligonucleotides