The immunophenotypic and immunogenotypic B-cell differentiation arrest in bone marrow of RAG-deficient SCID patients corresponds to residual recombination activities of mutated RAG proteins

Blood. 2002 Sep 15;100(6):2145-52.

Abstract

The protein products of the recombination activating genes (RAG1 and RAG2) initiate the formation of immunoglobulin (Ig) and T-cell receptors, which are essential for B- and T-cell development, respectively. Mutations in the RAG genes result in severe combined immunodeficiency disease (SCID), generally characterized by the absence of mature B and T lymphocytes, but presence of natural killer (NK) cells. Biochemically, mutations in the RAG genes result either in nonfunctional proteins or in proteins with partial recombination activity. The mutated RAG genes of 9 patients from 7 families were analyzed for their recombination activity using extrachromosomal recombination substrates, rearrangement of endogenous Ig loci in RAG gene-transfected nonlymphoid cells, or the presence of Ig gene rearrangements in bone marrow (BM). Recombination activity was virtually absent in all 6 patients with mutations in the RAG core domains, but partial activity was present in the other 3 RAG-deficient patients, 2 of them having Omenn syndrome with oligoclonal T lymphocytes. Using 4-color flow cytometry, we could define the exact stage at which B-cell differentiation was arrested in the BM of 5 RAG-deficient SCID patients. In 4 of 5 patients, the absence of recombination activity was associated with a complete B-cell differentiation arrest at the transition from cytoplasmic (Cy) Igmu(-) pre-B-I cells to CyIgmu(+) pre-B-II cells. However, the fifth patient showed low frequencies of precursor B cells with CyIgmu and surface membrane IgM, in line with the partial recombination activity of the patient's mutated RAG gene and the detection of in-frame Ig gene rearrangements in BM.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • B-Lymphocytes / cytology*
  • B-Lymphocytes / drug effects
  • Bone Marrow Cells / immunology*
  • Case-Control Studies
  • Cell Differentiation / drug effects
  • Child, Preschool
  • DNA-Binding Proteins / genetics*
  • DNA-Binding Proteins / pharmacology
  • DNA-Binding Proteins / physiology
  • Family Health
  • Female
  • Flow Cytometry / methods
  • Gene Rearrangement / drug effects
  • Gene Rearrangement / genetics
  • Genes, Immunoglobulin
  • Genotype
  • Homeodomain Proteins / genetics*
  • Homeodomain Proteins / pharmacology
  • Homeodomain Proteins / physiology
  • Humans
  • Immunophenotyping
  • Infant
  • Male
  • Mutation
  • Nuclear Proteins
  • Severe Combined Immunodeficiency / genetics
  • Severe Combined Immunodeficiency / immunology
  • Severe Combined Immunodeficiency / pathology*

Substances

  • DNA-Binding Proteins
  • Homeodomain Proteins
  • Nuclear Proteins
  • RAG2 protein, human
  • V(D)J recombination activating protein 2
  • RAG-1 protein