Description of a polymorphism in the regulatory region of the HLA-DRA gene

It was previously reported that the cell membrane expression of HLA class II molecules is tissue specific and variable among individuals. This variation could be explained at the level of gene regulation. Due to the fact that a coordinate regulation of the HLA-DR genes seems to exist, we focused on the HLA-DRA monomorphic gene. In order to study the polymorphism of the HLA-DRA gene regulatory region, we used restriction fragment length polymorphism analysis of polymerase chain reaction (PCR)-amplified genomic DNA. The DdeI and PvuII digestions of the amplified DNA permitted the definition of the two alleles according to the absence (allele A) or the presence (allele B) of the two polymorphic restriction sites. The presence of these sites was confirmed by direct sequencing after PCR. Using homozygous typing cells, a close relationship between the HLA-DRB coding region and the HLA-DRA regulatory region polymorphisms was shown. Furthermore, a linkage between the HLA-DRA regulatory region and DRB3 gene coding region polymorphisms could be established. These results suggested a structural argument for different levels of HLA class II genes and, consequently, of cell-surface expression of class II antigens according to the allelic specificities of DRA, DRB1, and DRB3.

DdeI polymorphism in the HLA-DRA regulatory region

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Anti-F(ab')2 antibody response to the injection of anticlass II HLA alloantibodies in patients with rheumatoid arthritis

Placenta eluted gamma globulins (PEGG) contain antibodies against class II HLA antigens and have been used for treating patients with rheumatoid arthritis (RA). In view of the potential use of antibodies to class II HLA for treating autoimmune diseases we looked for the immunobiological effects of PEGG injections in patients. No modulation of class II HLA was seen at the surface of circulating mononuclear cells after one week of daily PEGG injections. In some patients, antibodies to F(ab')2 fragments of PEGG-IgG were produced. These antibodies reacted against F(ab')2 of any IgG as well and did not prevent anticlass II HLA antibodies from binding to class II HLA, thus showing no characteristics of classical antiidiotypic antibodies. The appearance of anti-F(ab')2 antibodies was not correlated with the clinical course of the disease. Their significance is discussed.

Use of glucose-6-phosphate dehydrogenase as a new label for nucleic acid hybridization reactions

We describe here a sensitive new procedure for detecting DNA hybridization by dot blots. The method utilizes DNA or oligonucleotide probes labeled with biotin, sulfone, or haptens that can be detected by glucose-6-phosphate dehydrogenase (G6PDH) conjugates. Biotin labeling of DNA gave the best sensitivity. G6PDH activity was revealed by staining or by bioluminescence using an FMN oxidoreductase and a luciferase from Beneckea harveyi. Bioluminescent detection offered better sensitivity and faster revelation than the colorimetric assay and was found to be very useful in visualizing single mutations in human DNA after hybridization with an allele-specific biotinylated oligonucleotide probe. Revelation can be performed using a luminometer, photographic films, or a very sensitive video camera. The detection is limited by the nonspecific binding of the labeled reagent (streptavidin or antibodies). This limit is similar to that obtained with other nonisotopic labeling procedures, but our method is faster and several hybridization reactions can be performed on the same support.

A method of HLA class II typing using nonradioactive labelled oligonucleotides

The typing of HLA class II genes using molecular biology techniques has brought undoubtedly new insights in the analysis of their polymorphism. Particularly interesting is the dot-blot analysis of enzymatically-amplified genomic DNA hybridized with sequence-specific oligonucleotides. In order to use this technique of typing on a routine basis, we established a non-radioactive detection method of enzymatically-amplified genomic DNA dot-blots. We could clearly demonstrate that, using biotin-labelled specific oligonucleotides, it was possible to specifically discriminate between DQB1 first domain DNA sequences displaying three, two or even only one base-pair difference at a given codon position. The very satisfactory sensitivity level reached by this non-radioactive detection method could safely allow its use for clinical applications of HLA typing at the DNA level.

Increase of class II HLA molecules on the membrane of B lymphocytes from patients with rheumatoid arthritis

Using a novel cytofluorometric method of cellular antigen quantification, we examined peripheral blood mononuclear cells (PBMC) from patients suffering from rheumatoid arthritis (RA) for quantitative modification of class II human leucocyte antigen (HLA) molecules expressed on the surface. Class II HLA molecules were detected by indirect immunofluorescence with a monomorphic monoclonal antibody. No change was observed in the density of class II HLA molecules at the surface of monocytes of RA patients as compared to that of paired healthy subjects. We confirmed that the percentage of class II HLA-bearing T cells was slightly increased in RA patients versus controls, but the density of class II antigens per cell could not be determined accurately. An increase in the density of class II HLA molecules on RA B cells was shown, suggesting that a chronic activation stage of this population contributes to the disease.

[Effect of antibiotics on T lymphocyte responses]

T lymphocytes play a central role in the immune response. Coming from the bone marrow, they are attracted by the thymus where they are educated, they mature and differentiate into two main subsets: helper T-cells and suppressor/cytotoxicity T-cells. T lymphocytes are involved in the immune response at different levels. As "conductor" of the whole lymphoid system, they are able to recognize foreign antigens and to induce the activation and the regulation of other T-cells and also B cells by the way of many soluble factors named lymphokines. As effector cells of cell-mediated immune responses, they are able to provoke delayed type hypersensitivity reactions and to specifically kill target cells (anti-viral cytotoxicity, for instance). The in vitro effect of some antibiotics on T-cells has been investigated. Clearly, a lot of them are able to modulate T-cell functions.

[Reinfection after rubella and congenital polymalformation syndrome]

A case is reported of a term newborn with intra uterine growth retardation and numerous malformations such as complex heart disease, abnormalities of distal limbs, cleft palate. Death occurred after two days. The diagnosis of rubella embryopathy was confirmed by the following criteria: a high level of rubella antibodies in mother and newborn (1/1000) an isolation of rubella virus from the infant's urine. Diagnosis of rubella after reinfection was documented by a high level of antibodies in the mother three years before this pregnancy. Other observations reported in literature confirm the extreme rarity of congenital rubella after reinfection.

[Infectious endocarditis in the neonatal period]

A case of bacterial endocarditis in a newborn without any congenital heart disease is reported. The clinical diagnosis was suspected on evolutive heart failure by mitral dysfunction with sepsis. T.M. mode echocardiography could detect only the valvular defects. Correlations between anatomic and echocardiographic findings allowed to discuss the limits of the method. Neonatal bacterial endocarditis is a rare event. Its diagnosis is difficult and its prognosis very poor. This affection must be prevented.

[Streptococcus group B neonatal infection and postnatal diaphragmatic hernia]

The authors report a case of post natal hernia with group B beta hemolytic streptococcus infection. The frequency of such an association compared to the rarity of delayed onset congenital diaphragmatic hernia may constitute a reflexion subject. The literature is reviewed and a concept of pathogenesis is discussed.