G. de Saint Basile

Increased radiosensitivity of granulocyte macrophage colony-forming units and skin fibroblasts in human autosomal recessive severe combined immunodeficiency.

We studied the radiosensitivity of granulocyte macrophage colony-forming units (GM-CFU) in patients with a severe combined immunodeficiency (SCID). Three patients lacking both mature T and B cells showed a twofold higher GM-CFU radiosensitivity calculated as the DO value (dose required to reduce survival to 37%), and an identical observation was made with fibroblasts from one of these patients. A patient with an SCID with hypereosinophilia, i.e., Omenns syndrome characterized by extremely restricted T cell heterogeneity and a lack of B cells, also showed abnormal GM-CFU radiosensitivity. In contrast, GM-CFU from a patient lacking only T cells (X-linked form of SCID) showed normal GM-CFU radiosensitivity. These data further support the similarity between human T(-) B(-) SCID and the murine acid mutation characterized by a defect in T cell receptor and immunoglobulin gene rearrangement, and by an abnormal double-strand DNA break repair function. In addition, they strongly suggest that the Omenns immunodeficiency syndrome may be a leaky T(-)B(-) SCID phenotype as previously indicated by the coexistence of the two phenotypes in siblings.

Close linkage of probe p212 (DXS178) to X-linked agammaglobulinemia.

SummarySegregation analysis was performed in three families affected in X-linked agammaglobulinemia (XLA) with five polymorphic DNA probes linked to the disease locus. In agreement with previous studies, no recombination was observed with either pXG12 (DXS94) or S21 (DXS17). Segregation analysis was also performed with a marker, p212 (DXS178), which has been shown to be closely linked to pXG12 in normal families. No cross-over with XLA was observed in these three families and in five additional families previously analyzed with DXS17 and DXS94 (z = 5.92 at θ = 0). These data provide evidence against genetic heterogeneity in XLA and indicate the value of probe p212 for carrier detection and prenatal diagnosis of XLA. We were able to estimate the carrier status of six females (out of six) in the three previously unreported families.

Close linkage of random DNA fragments from Xq 21.3-22 to X-linked agammaglobulinaemia (XLA)

SummaryLinkage analysis of 15 families affected by X-linked agammaglobulinaemia (XLA) showed close linkage with three probes located towards the centre of the long arm of the X chromosome. No cross-overs were found using pXG12 (DXS94) lod 6.6 or S21 (DXS17) lod 4.4. One cross-over was found with 19.2 (DXS3). This confirms and extends a previous linkage study (Kwan et al. 1986) which demonstrated linkage with S21 and 19.2. Of the families 14 were informative for either pXG12 or S21 and these probes should thus be of great diagnostic value. No evidence of heterogeneity was found in the XLA families but several cross-overs within this region were detected in a family with the X-linked hyper-IgM syndrome confirming this disease as a separate clinical entity.

Control of human B cell tumor growth in severe combined immunodeficiency mice by monoclonal anti-B cell antibodies.

Severe combined immunodeficiency (scid) mice develop EBV (+)B cell tumors after infusion of EBV(+)B cells or of B cells and EBV. In this study, scid mice were infused with B cell lines derived from three patients who developed a B lymphocyte proliferative disorder after bone marrow or organ transplantation. Intraperitoneal injection of 5 x 10(6) B cells induced tumor growth in all mice, leading to death within 60 d. Human B cells were identified in spleen and bone marrow by means of immunofluorescence or EBV genome amplification, and human IgM was detected in serum. Infusion of murine monoclonal antibodies specific for human B cell membrane antigens CD21, CD24, and CD23 was effective in 80% of animals, against two of the three cell lines preventing tumor development or inducing remission according to the time of treatment. The effect was antibody dose dependent and was optimal with four intravenous infusions of at least 0.1 mg 4 d apart. Human IgM in serum and human B cells in spleen and bone marrow became undetectable when peritoneal tumors regressed completely. Infusions of IgG1 isotype-matched anti-CD4 antibody or anti-CD3 antibody had no effect. Tumors developed or recurred in 50% of these animals injected with one of the B cell line 3 mo after treatment was stopped. The same anti-CD21 and anti-CD24 antibodies had been used to treat the three patients, and shown similar degrees of effectiveness as in the scid mouse model. These results indicate that scid mice may be suitable for assessing therapeutic approaches to human B cell proliferation.

Founder effect for a 26-bp deletion in the RFXANK gene in North African major histocompatibility complex class II-deficient patients belonging to complementation group B

Abstract Expression of major histocompatibility complex (MHC) class II genes is controlled at the transcriptional level by at least four trans-acting genes, CIITA, RFXANK, RFX5, and RFXAP. Defects in these regulatory genes result in the absence of MHC class II molecule expression and, thereby, cause a combined immunodeficiency. MHC class II deficiency is inherited as an autosomal recessive trait. Since the first description of the disease, about 70 patients from 50 families have been reported. Forty-three of these families have been classified into four complementation groups: A, B, C, and D. In the largest group, B, the majority of patients are of North African origin. In two of these patients, the same mutation in the RFXANK gene (752delG-25) was identified. We performed a mutation analysis in 20 additional patients belonging to complementation group B and detected the 752delG-25 mutation in 17. All of these patients are of North African origin. A founder effect for this mutation was documented, since all tested patients, except one, display a common haplotype spanning the RFXANK locus.

Wiskott-Aldrich syndrome carrier detection with the hypervariable marker M27β

SummaryWhole-blood cells of obligate carriers of the X-linked Wiskott-Aldrich syndrome (WAS) exhibit nonrandom inactivation of the X-chromosomes. However, because of the limited polymorphism of the probes available, the X-methylation pattern can only be determined in a restricted proportion of females. We thus analysed a large set of normal females and members of WAS families, using the recently described marker M27β, which detects the hyperpolymorphic locus DXS255. The probe was used to detect differences in methylation between the active and inactive X-chromosome, and the findings were compared with the pattern obtained using the well-documented probes from the 5′ end of the PGK and HPRT genes. All the normal females were found to use either X-chromosome randomly, and there was complete correlation between the three probes in the populations studied. Segregation analysis performed with M27β and other related markers in the WAS families was fully in accordance with the X-inactivation data. The use of M27β, for both X-inactivation and segregation analysis of WAS kindreds, provides a basis for genetic counselling in the majority of families, including those with no surviving males.

Ichthyosis as the dermatological phenotype associated with TTC7A mutations

DEAR EDITOR, The phenotype associated with spontaneous mutation in the tetratricopeptide repeat domain 7A gene (Ttc7) in flaky skin (fsn) mice combines gastric hyperplasia, hyperproliferative immune disorder and skin anomalies. All fsn mice progressively develop thick white scales and patchy alopecia that turns into papulosquamous lesions, marked hyperkeratosis and hypergranulosis associated with a dermal mixed inflammatory infiltrate on skin biopsy. Currently the fsn mouse constitutes a model for human psoriasis vulgaris. In humans, TTC7A mutation was recently shown to cause a rare autosomal recessive inherited condition combining an immunodeficiency and an enteropathy of variable intensity (MIM 243150). We observed that some patients with TTC7A deficiency also develop dermatological features. We thus characterized the dermatological features presented by TTC7A-deficient patients, which were compared with those found in fsn mice.

Antibody levels to candida albicans carbohydrate and major cytoplasmic antigens isolated from standard and patient strains

A solid phase radioimmunoassay (RIA) and ELISA were used to detect human antibodies to Candida albicans (CA) organisms or purified fractions, namely, carbohydrate-rich fraction (CRF) and cytoplasmic peptides (SSF) of CA. IgG antibodies to either whole organisms or to CRF were found in sera obtained from patients with chronic mucocutaneous candidiasis (CMCC) or digestive candidiasis, as well as in healthy control sera. In patient sera, no correlation between the clinical stage of disease and the IgG anti-CRF levels was found. In contrast, antibodies to SSF were absent in healthy control sera. IgM anti-SSF in the absence of IgG anti-SSF were found in sera of patients with recent digestive candidiasis, and low levels of IgM and IgG Ab were detected in sera of CMCC patients. The lack of correlation between IgG anti-CRF levels and clinical status can, in part, be explained by the individual variability of Candida strains and by the inadequacy of the laboratory standard antigens in the antibody assays used. The clinical relevance of different tests to detect anti-CA antibodies is discussed.

Familial haemophagocytosis lymphohisticytosis type 3: A case report

Familial hemophagocytic lymphohistiocytosis (FHL) is a rare autosomal recessive disorder of immune regulation. Here, we report on a fatal case of type 3 FHL (FHL3) in a 45-day-old boy. Clinically, the infant presented with fever and hepatosplenomegaly. Biology showed pancytopenia, elevated ferritin, and decreased fibrinogen. Images of hemophagocytosis were found at the bone morrow examination. The diagnosis of FHL type 3 was made by the identification of homozygous mutation in the Munc13-4 gene (UNC13D) located in exon 20: 1822 del 12bp (V608fs). This mutation was previously observed in a Tunisian and in Moroccan families.

Cytophagic histiocytic panniculitis: is it a macrophage activation syndrome in situ?

Patients A 10-month-old year boy and a 4-month-old-year girl presented with multiple erythematous and indurated noduless on the limbs, and developed high-grade fever and biological features suggestive of MAS several months after the onset of cutaneous disease. Serologic test for EBV was negative and bone marrow examination revealed hemophagocytosis. A homozygous splicing mutation for the UNC13D gene encoding for Munc 13-4 was present in patient 1, but NK cell cytotoxicity and degranulation assays, and expression of Munc 13-4 protein were normal. No mutation was found in Patient 2. Prednisone alone failed to induce a sustained remission which was obtained by adding cyclosporine A.