Mutations of CD40 gene cause an autosomal recessive form of immunodeficiency with hyper IgM.

CD40 is a member of the tumor necrosis factor receptor superfamily, expressed on a wide range of cell types including B cells, macrophages, and dendritic cells. CD40 is the receptor for CD40 ligand (CD40L), a molecule predominantly expressed by activated CD4(+) T cells. CD40/CD40L interaction induces the formation of memory B lymphocytes and promotes Ig isotype switching, as demonstrated in mice knocked-out for either CD40L or CD40 gene, and in patients with X-linked hyper IgM syndrome, a disease caused by CD40L/TNFSF5 gene mutations. In the present study, we have identified three patients with an autosomal recessive form of hyper IgM who fail to express CD40 on the cell surface. Sequence analysis of CD40 genomic DNA showed that one patient carried a homozygous silent mutation at the fifth base pair position of exon 5, involving an exonic splicing enhancer and leading to exon skipping and premature termination; the other two patients showed a homozygous point mutation in exon 3, resulting in a cysteine to arginine substitution. These findings show that mutations of the CD40 gene cause an autosomal recessive form of hyper IgM, which is immunologically and clinically undistinguishable from the X-linked form.

Immune function in patients with beta thalassaemia receiving the orally active iron-chelating agent deferiprone.

Short-term deferiprone may reduce body iron in some patients with thalassaemia major. Concerns regarding potential immunosuppressive effects of deferiprone have been raised from results of animal studies and case reports in humans. We studied immune function in 57 thalassaemia patients: 36 treated with deferiprone (L1; CP020) and 21 treated with desferrioxamine (DFO). Circulating B lymphocytes were increased in all patient groups. No differences were detected between treatment groups in percentages of circulating lymphocytes, concentrations of IgG, IgM or IgA, specific antibody titres, complement levels, or in vitro lymphocyte proliferation. No clinically important infections were observed in any patient. These data suggest that no clinical or laboratory changes consistent with immuno-suppression or immunodeficiency are observed during deferiprone therapy.

Three new adenosine deaminase mutations that define a splicing enhancer and cause severe and partial phenotypes: implications for evolution of a CpG hotspot and expression of a transduced ADA cDNA.

We report three novel adenosine deaminase (ADA) mutations with interesting implications. A Somali child with severe combined immunodeficiency disease (SCID) had reduced ADA mRNA in T cells and was homozygous for the nonsense mutation Q3X. Unexpectedly, her healthy father was a compound ADA heterozygote whose second allele carried a 'partial' mutation, R142Q, due to a G-->A transition of a CpG dinucleotide. A C-->T transition of the same CpG produced a nonsense mutation, R142X, in two homozygous Canadian Mennonite infants with SCID. The severe and healthy phenotypes associated with R142X and R142Q, the high frequency of 'partial' ADA mutations arising from CpGs in healthy individuals of African descent and the presence of CAA (glutamine) at codon 142 in murine ADA, suggest selection for replacement of this CpG hotspot by CpA during ADA evolution. R142X, located within a purine-rich segment at nt 62/116 of exon 5, caused skipping of the exon, possibly by disrupting a splicing enhancer. Absence of exon 5 in T cell ADA mRNA and low ADA activity in T cells and erythrocytes obtained at age 18-22 months from one of the Mennonite children, indicate limited expression of a normal ADA cDNA from retrovirally transduced CD34+ umbilical cord leukocytes infused shortly after birth in an attempt at stem cell gene therapy.

Severe illness caused by Rickettsia conorii.

An 18-month-old boy presented with a 5-day history of lethargy, fever, vomiting and rash. He required intensive care for inotropic and ventilatory support. He developed a disseminated intravascular coagulopathy and gangrene of his extremities. In addition, he had severe neurological dysfunction and loss of vision, both of which recovered spontaneously with time. The potential severity of tick typhus caused by Rickettsia conorii is described as well as the importance of paired serological tests in the diagnosis of this condition.

Selective culture of primate marrow-derived macrophages in medium devoid of protein additives.

Viable cultures of bone marrow-derived macrophages (BMM phi) from a primate source, the baboon, were maintained for up to 4 weeks in culture in the absence of any exogenous protein in the medium. Baboon peripheral blood monocytes, spleen, lung, and liver M phi s or human BMM phi failed to survive for greater than 4 days. The protein-free BMM phi cultures were morphologically distinctive by virtue of the extremely dendritic appearance of the M phi s. In contrast baboon marrow cultured in the presence of fetal calf serum led to the overgrowth of fibroblastoid cells and in the presence of horse serum produced numbers of giant cells or polykaryocytes in addition to M phi s. The BMM phi were capable of nonimmune phagocytosis of yeast particles, expressed Ia antigen on their surfaces (59%), and were positive cytochemically for nonspecific (alpha-naphthyl acetate) esterase, oil red O, and tartrate resistant acid phosphatase. The addition of sera to established protein-free BMM phi cultures induced a rapid change of shape, viz., retraction of the dendritic processes and rounding up of the M phi s apparent within 10 min. This shape change was not induced by the addition of hemopoietic growth factors granulocyte-macrophage colony-stimulating factor (GM-CSF), granulocyte CSF (G-CSF), macrophage CSF (M-CSF), or interleukin 3 (IL-3), nor could it be inhibited by the calcium channel blocking agent Nifedipine. Low levels of M-CSF activity, assayed by the murine bone marrow proliferation assay, were detected in the supernatant.