Immunoglobulin heavy chain gene rearrangements in X‐linked agammaglobulinemia

Abstract

Physicians and Surgeons, New YorkX-linked agammaglobulinemia (XLA) appears to involve a defect in human B lymphocyte differentiation which is manifested at the pre-B cell stage. The defect segregates as an X-linked recessive trait but is not a single genetic entity. IgM-producing B cell clones were established by Epstein-Barr virus transformation of peripheral blood mononuclear cells of patients with the XLA defect linked to the DXS3 and DXS17 chromosomal loci. Individual XLA B cell clones were demonstrated to have rearrangements of the JH regions of both immunoglobulin VH region loci. The rearranged J H regions of the B cell clone ALA 19 were molecularly cloned and their nucleotide sequence was determined. Both &-associated rearrangements (designated 191 and 192) resulted from the juxtaposition of variable (VH), diversity (D) and joining (JH) segments (VHDJH rearrangements). The 191 rearrangement employed a VH segment belonging to VH subgroup 111 and a J H~ segment. The 192 rearrangement employed a VHII and a J H~ segment. The D191 and D192 segments encompassed 21 and 28 nucleotides, respectively, and showed little homology to each other or to previously reported human D sequences. Surprisingly, both VHDJH complexes had open reading frames. However, in accord with principles of allelic exclusion, only the 191 allele was detectably expressed in the total RNA of the cell. A possible mechanism for the lack of expression of the 192 allele is discussed. We conclude that the DXS3-DXS17-linked XLA defect does not preclude VH to DJH rearrangements or the expression of VH containing heavy chain molecules.

Bone marrow cells in X-linked agammaglobulinemia express pre-B-specific genes (lambda-like and V pre-B) and present immunoglobulin V-D-J gene usage strongly biased to a fetal-like repertoire.

“…These results are in agreement with previous phenotypic characterization ofthe bone marrow cell population in XLA patients (62,63). By contrast to other reports (3,9,49,64), our data indicate that rearrangement mechanisms seem fully functional, although a possible decrease in efficiency ofthe pro-B to pre-B transition, as followed by the DJ to VDJ rearrangement cannot be quantitatively as- Our analysis performed on XLA bone marrow cells provides direct access to the pre-B cell repertoire which is truly representative of the defect. Analysis of EBV clones derived from XLA patients may therefore contain a bias linked to the selection ofa minor population of B cells that have escaped the XLA defect (1 1, 12).…”

“…Analysis of the X chromosome inactivation in XLA carrier women has shown that the defect was specific to the B cell lineage (3)(4)(5)(6)(7). The exact nature of the defect is, however, not known.…”

“…Although truncated heavy chains have been identified earlier (9), the recombinases that direct Ig and T cell receptor (TCR) gene rearrangement do not seem to be affected by the XLA gene since the T cell compartment appears to be normal (8). More recent reports have shown that the IGH locus could recombine, and that some Epstein-Barr virus (EBV)-transformed cell lines could be derived from XLA patients, suggesting that block of the B cell maturation was leaky (3,(10)(11)(12)(13).…”

Long-Term Study of a Female Hyper-IgM Immunodeficiency

“…In X-linked agammaglobulinemia some sequences of the junctions in VDJ rearrangements have been reported [15][16][17]. In this patient, the sequences examined in the junctions of VDJ rearrangements were in frame, and N insertion was also detected.…”

B-cell and T-regulatory cell dysfunction in six Chinese children with hypogammaglobulinaemia

“…Epstein-Barr virus-transformed B-cell lines from patients with XLA have been shown to secrete IgM constitutively or in response to B-cell growth and differentiation factors [10], indicating that failure of B-cell differentiation is not absolute. Furthermore, EBV-transformed B-cell lines from XLA patients were able to form complete VnDJH rearrangements [11]. An adequate yield of Bcells was obtained from patient 1, and these gave very low IgG and IgA PFC, and slightly low IgM PFC, when co-cultured with (C) Tn and PWM.…”