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Immunoglobulin gene expression in xid mice: defective expression of secreted and membrane alpha-heavy chain RNA
1Department of Immunology, Mayo Clinic, Rochester, MN 55905.
CNA/N mice bearing the X-linked immunodeficiency (xid) gene(s) demonstrate overall decreased numbers of B-cells, impaired immune responses to TI-2 antigens and decreased serum IgM, IgG3 and to a lesser extent IgG1 and IgA. In these experiments we examined equal number of B-cells (cells capable of regeneration of surface Ig) from PP, MLN and spleens of xid and control mice for immunoglobulin gene expression. B-cells present in CBA/N mice exhibit control levels of Ig isotype-specific mRNA accumulation and transcription. Oligonucleotide probes directed against membrane and secreted exons of mu, gamma and alpha genes were synthesized and hybridized to B-cell RNA from CBA/N and CBA/J mice to determine relative levels of each isotype- and exon-specific mRNA. Results revealed decreased alpha s RNA: alpha m RNA in splenic B-cells of xid mice when compared to control animals. Northern blot analysis of total tissue polysomal RNA demonstrated enhanced expression of the (larger) membrane form of alpha-mRNA (alpha m-RNA) of CBA/N when compared to CBA/J mice. This was especially apparent in splenic preparations; these and other studies have shown that both control and xid PP and MLN express enhanced levels of the membrane forms of each Ig heavy chain isotype RNA when compared to splenic RNA levels. These data suggest the presence of a defective regulation of membrane and secreted alpha in B-cell subpopulations of xid mice.
CNA/N mice bearing the X-linked immunodeficiency (xid) gene(s) demonstrate overall decreased numbers of B-cells, impaired immune responses to TI-2 antigens and decreased serum IgM, IgG3 and to a lesser extent IgG1 and IgA. In these experiments we examined equal number of B-cells (cells capable of regeneration of surface Ig) from PP, MLN and spleens of xid and control mice for immunoglobulin gene expression. B-cells present in CBA/N mice exhibit control levels of Ig isotype-specific mRNA accumulation and transcription. Oligonucleotide probes directed against membrane and secreted exons of mu, gamma and alpha genes were synthesized and hybridized to B-cell RNA from CBA/N and CBA/J mice to determine relative levels of each isotype- and exon-specific mRNA. Results revealed decreased alpha s RNA: alpha m RNA in splenic B-cells of xid mice when compared to control animals. Northern blot analysis of total tissue polysomal RNA demonstrated enhanced expression of the (larger) membrane form of alpha-mRNA (alpha m-RNA) of CBA/N when compared to CBA/J mice. This was especially apparent in splenic preparations; these and other studies have shown that both control and xid PP and MLN express enhanced levels of the membrane forms of each Ig heavy chain isotype RNA when compared to splenic RNA levels. These data suggest the presence of a defective regulation of membrane and secreted alpha in B-cell subpopulations of xid mice.