Christophe Demaison

ANALYSIS OF HUMAN VH GENE REPERTOIRE EXPRESSION IN PERIPHERAL CD19+ B CELLS

Using CD19 B-cell selection and polymerase chain reaction-amplified cDNA libraries, we analyzed the peripheral immunoglobulin heavy chain variable repertoire of three healthy adult donors. Here we report that most of the CD19+ circulating B cells expressed unmutated VH-D-JH rearrangements. By specific VH family hybridization, we show that VH gene family utilization in the periphery roughly corresponds to the complexity of these families in the germline and appears to be relatively constant among the analyzed subjects. However, sequence data of clones picked at random from one IgM cDNA library reveals that in spite of this “random” utilization, the VH gene expression in naive circulating B cells is highly biased towards the expression of a limited set of VH genes. As previously reported by others, this restricted mechanism is also found for the D and JH segments.

Clonotypic dominance and variable gene elements of pathogenic anti-DNA autoantibodies from a single patient with lupus

This study explores the usage and diversity of the variable gene elements expressed by human lupus antibodies to DNA bearing the 0–81 idiotype, a marker of pathogenic anti‐DNA autoantibodies. Rather than studying DNA‐specific clonotypes from different patients, a panel of idiotype positive anti‐DNA autoantibody‐secreting clones from a single individual were analysed. By cloning and nucleotide‐sequeneing the heavy‐chain variable gene segments, evidence was found for dominance of clonotypic patterns. Also noted was a high rate of diversification among the variable (VH), diversity (Dh) and junctional (JH) gene segments utilized, with a pattern of mutations indicative of antigenic selection. These features suggest that the clones secreting the lupus pathogenic autoantibodies have been selected over multiple generations through an affinity‐maturation process that is reminiscent of antigen‐driven immune responses.

The heavy chain variable region genes of human lupus autoantibodies

An important role of the immune system is to distinguish “self” from “non-self” and to act as a first-line of defense against external agents. To cope with the diversity of the potentially antigenic molecules of the environment and those of self-components, the immune system requires a powerful discriminatory ability. In normal conditions, mature B cells respond to antigen stimulation, yet must avoid high-affinity recognition of self-antigens that may lead so aggressive autoimmunity. No mechanism fully accounts for this phenomenon.