The influence of CD40-CD154 interactions on the expressed human V(H) repertoire: analysis of V(H) genes expressed by individual B cells of a patient with X-linked hyper-IgM syndrome..     ///    These results have suggested that specific influences on the composition of the V(H) repertoire in normals require CD40-CD154 interactions..     ///     Analysis of the V(H)DJ(H) repertoire of peripheral blood IgM(+) B cells from a patient with X-linked hyper-IgM syndrome (X-HIgM) was undertaken to determine whether the distribution of V(H) families in the productive repertoire might be regulated by in vivo CD40-CD154 interactions. 