Early human IgH gene assembly in Epstein-Barr virus-transformed fetal B cell lines. Preferential utilization of the most JH-proximal D segment (DQ52) and two unusual VH-related rearrangements

Pathogenic anti-DNA antibodies in SLE: idiotypic families and genetic origins

We have adopted an idiotypic approach to study the double stranded DNA (dsDNA) binding antibodies of systemic lupus erythematosus (SLE). Three anti-idiotypic reagents, 8.12, 3I, and F4, identify cross reactive idiotypes that are each expressed on anti-dsDNA antibodies in the sera of many patients with SLE. These idiotypic antibodies are implicated in the pathogenesis of SLE as they are present in immune complex deposits in the kidneys of patients with SLE glomerulonephritis. The autoantibody associated idiotypes are also expressed on antibodies that do not bind DNA. We are investigating the origin of the pathogenic anti-dsDNA antibodies of SLE by comparing the autoantibodies, the antibodies to foreign antigens, and the myeloma proteins that express each SLE associated idiotype. In conjunction with serological analysis of these idiotypic systems, molecular genetic studies indicate that both the 8.12 and the 3I autoantibody associated idiotypes may be germline encoded, while the F4 idiotype is generated by somatic mutation. The data further suggest that the antigenic specificity of the pathogenic anti-DNA antibodies of SLE is acquired through somatic mutation of germline immunoglobulin genes. By studying the regulation of genes capable of encoding pathogenic autoantibodies, in both SLE patients and non-autoimmune individuals, we may be able to elucidate the pathogenesis of autoimmune disease and begin to design more effective therapeutic interventions.

A human anti-cardiolipin autoantibody is encoded by developementally restricted heavy and light chain variable region genes

Based on recent structural analyses of monoclonal autoantibodies, it appears that a number of these antibodies express germ-line immunoglobulin variable region (V) genes with little or no somatic mutation. In addition, our group and others have noted the identity or near identity of some autoantibody-associated V genes to V genes apparently expressed preferentially in the fetal pre-B cell repertoire. To extend these data, we now report that the heavy and light chain V genes of an anti-cardiolipin antibody derived from a healthy individual display 99% nucleotide sequence homology with V genes expressed in early B cell ontogeny. Sequence comparisons indicate the likely use of fetal-restricted V genes by this autoantibody. Taken together with other data on autoantibody V gene usage, these findings provide further evidence for overlap between the autoantibody-associated and early ontogeny expressed V gene repertoires and suggest that natural autoreactivity may be instrumental in the development and maintenance of the normal immune repertoire.

Autoantibodies encoded by the most Jh-proximal human immunoglobulin heavy chain variable region gene

Little is known about the utilization of human Ig heavy chain variable gene segments (VH segments) in different B-lineage cell populations or in antibodies of particular specificity and function. We now demonstrate that human antibodies with Ig VH regions encoded by the most JH-proximal human VH segment (VH6) have specificities resembling those of autoantibodies present in sera of patients with systemic lupus erythematosus (e.g., anti-DNA and anticardiolipin). These specificities appear to be encoded by the germline VH6 gene because the activity was found in multiple independent VH6 antibodies in which the light chain varied with respect to isotype and V kappa subgroup. Features of CDR3 length and somatic mutation patterns in several VH6 antibodies suggested that they were selected by the immune system.

Growing human B-cell precursors in vitro: the continuing challenge

Methods for propagating murine B-cell precursors in vitro have been instrumental in unraveling the cells and molecules regulating murine B-cell ontogeny. However, similar methods are not available for studying human B-cell ontogeny. Here, Tucker LeBien discusses why efforts to grow human B-cell precursors in vitro have been largely unsuccessful and proposes alternative strategies that may prove useful.