sq-23377 and Hypergammaglobulinemia

X-linked hyper IgM syndrome (XHIM) is a primary immunodeficiency disorder caused by mutations of the gene encoding CD40 ligand (CD40L). We correlated mutations of the CD40L gene, CD40L expression, and the clinical manifestations observed in XHIM patients from 30 families. The 28 unique mutations identified included 9 missense, 5 nonsense, 9 splice site mutations, and 5 deletions/insertions. In 4 of 9 splice site mutations, normally spliced and mutated mRNA transcripts were simultaneously expressed. RNase protection assay demonstrated that 5 of 17 mutations tested resulted in decreased levels of transcript. The effect of the mutations on CD40L expression by activated peripheral blood mononuclear cells (PBMC) and T-cell lines or clones was assessed using one polyclonal and four monoclonal antibodies and a CD40-Ig fusion protein. In most patients, the binding of at least one antibody but not of CD40-Ig was observed, suggesting nonfunctional CD40L. However, activated PBMC from three patients and activated T-cell lines from two additional patients, each with different genotype, bound CD40-Ig at low intensity, suggesting functional CD40L. Thus, failure of activated PBMC to bind CD40-Ig is not an absolute diagnostic hallmark of XHIM and molecular analysis of the CD40L gene may be required for the correct diagnosis. Patients with genotypes resulting in diminished expression of wild-type CD40L or mutant CD40L that can still bind CD40-Ig appear to have milder clinical consequences.

Topics: Adolescent; Adult; Animals; Antibodies, Viral; Bacteriophage phi X 174; CD4-Positive T-Lymphocytes; CD40 Antigens; CD40 Ligand; Child; Child, Preschool; COS Cells; Disease Susceptibility; DNA Mutational Analysis; Genotype; Humans; Hypergammaglobulinemia; Immunoglobulin M; Immunologic Deficiency Syndromes; Incidence; Infections; Ionomycin; Lymphocyte Activation; Male; Membrane Glycoproteins; Mutation; Phenotype; Point Mutation; Recombinant Fusion Proteins; Recurrence; RNA Splicing; RNA, Messenger; Sequence Deletion; Tetradecanoylphorbol Acetate; Transcription, Genetic; X Chromosome

The CD40 ligand expressed on activated T cells plays a pivotal role in B cell proliferation and differentiation. Mutations in the CD40 ligand gene, which alter its expression on the surface of activated T cells, are associated with the X-linked form of Hyper-IgM syndrome (XHIM). A rapid and simple, three-color whole blood flow cytometry procedure was developed for maximal expression and detection of the CD40L on the surface of in vitro activated CD4+ T cells. Approximately 90% of in vitro activated CD4+ T cells obtained from healthy controls expressed the CD40L compared to only 5% of in vitro activated CD4+ T cells obtained from the XHIM patients. The CD40L was expressed on approximately 50% of the in vitro activated CD4+ T cells obtained from the mothers of XHIM patients, consistent with a diagnosis of their carrier status. This is the first report of a whole blood procedure adapted for routine clinical use which is able to detect abnormal CD40L expression in XHIM patients and carriers.

Topics: Adult; Carcinogens; Carrier State; CD3 Complex; CD40 Antigens; CD40 Ligand; Female; Flow Cytometry; Genetic Linkage; Humans; Hypergammaglobulinemia; Immunoglobulin M; Ionomycin; Ionophores; Ligands; Lymphocyte Activation; Membrane Glycoproteins; Syndrome; T-Lymphocytes; Tetradecanoylphorbol Acetate; Up-Regulation; X Chromosome