Human thymic B cells largely overexpress the VH4 Ig gene family. A possible role in the control of tolerance in situ?
Human thymus contains a small population of B cells, a fraction of which expresses CD2 and/or CD5, as revealed by FACS analysis. Human thymic B cells enriched on CD19 panning revealed a constant co-expression of CD19 and Ig light chains. In the absence of detectable B precursors, these cells had reached at least the stage of IgM+ immature B lymphocytes. Analysis of Ig transcripts by PCR amplification first revealed a strong bias in favor of the VH4 and sequencing of 45 VH4-D-J cDNA clones isolated from two thymuses indicated that this thymic repertoire significantly differed from that of peripheral blood lymphocytes. Most genes of the VH4 family were used with various D-J combinations and a relatively high frequency of somatic mutations. This repertoire thus appears clearly selected in the thymus. This is of particular interest since the VH4 gene family is frequently encountered in autoimmunity a situation in which the number of thymic B cells is largely increased. They could play a major role in the control of tolerance in situ.
Tonnelle
C
C
Centre d'Immunologie INSERM, CNRS de Marseille Luminy, CIML, Marseille, France.
D'Ercole
C
C
Depraetere
V
V
Métras
D
D
Boubli
L
L
Fougereau
M
M
D018941:Antigens, CD19 / Q000032:analysis; D015551:Autoimmunity; D016175:B-Lymphocyte Subsets / Q000276:immunology*; D002675:Child, Preschool; D018076:DNA, Complementary / Q000235:genetics; D005786:Gene Expression Regulation; D015326:Gene Rearrangement, B-Lymphocyte, Heavy Chain; D005803:Genes, Immunoglobulin; D006801:Humans; D007108:Immune Tolerance; D007143:Immunoglobulin Heavy Chains / Q000096:biosynthesis* / Q000235:genetics; D007135:Immunoglobulin Variable Region / Q000096:biosynthesis* / Q000235:genetics; D007223:Infant; D007231:Infant, Newborn; D016133:Polymerase Chain Reaction; D013950:Thymus Gland / Q000166:cytology* / Q000276:immunology
D018941:Antigens, CD19; D018076:DNA, Complementary; D007143:Immunoglobulin Heavy Chains; D007135:Immunoglobulin Variable Region