Syndrome de sézary

The Sezary cell is a mature lymphocyte with a convoluted, cerebriform nucleus on cytomorphologic and ultrastructural samples. It is a major diagnostic feature of Sezary syndrome, clinically defined by the rapid onset of a pruriginous erythroderma with diffused adenopathies. Sezary cells can also reveal blood involvement by tumor cells in patients with mycosis fungoides. In a suggestive clinical context, peripheral blood smear examination is essential, whatever the results of the total blood count, to identify a significant percentage of characteristic cells. Most Sezary cells have a phenotype of mature memory T-lymphocytes, CD2⁺, CD3⁺, CD4⁺, CD5⁺, CD8⁻, CD45RO⁺, CD45RA⁻, TCR α/β⁺, but rarely they can also exhibit a CD8⁺CD4⁻ or CD4⁺CD8⁺ phenotype, and/or a lack of expression of CD2, CD3, CD4, or CD5 antigens. Patients with a Sezary syndrome often have an increase in CD4⁺ lymphocytes. The CD4⁺CD7⁻ population is also increased, but tumor cells have been identified both in the CD4⁺CD7⁺ and in the CD4⁺CD7⁻ populations. Sezary cells are found in the CD4⁺CD26⁻ population, but there are yet no specific phenotypic markers of Sezary cells. IL-7 is a growth factor for Sezary cells, and can induce the establishment of long-term tumor T-cell lines. We recently identified three other surface antigens on Sezary cells. The Natural Killer (NK) receptor CD158k/KIR3DL2/p140, normally expressed by NK and CD8⁺ T-cells was detected on the surface of CTCL cell lines as well as on freshly isolated CD4⁺ peripheral blood lymphocytes from SS patients. SC5 is a newly described activation-related intracellular inhibitory receptor expressed on the surface of a minor PBL subset. We found that SC5 expression was significantly increased in SS cells and correlated to p140 expression, ILT-2/CD85j is another inhibitory receptor expressed by tumor T-lymphocytes. Both SC5 and ILT-2 molecules are functional on CTCL cells, as their triggering in vitro leads to the recruitement of SHP-1 and to the specific inhibition of CTCL malignant cell proliferation induced by CD3/TCR stimulation. The expression of these antigens and the cytokine-induced upregulation of bcl-2 could partly explain the survival and the inhibition of the apoptosis of Sezary cells. Their identification on circulating SS tumor cells might be of importance both for the understanding of CTCL pathophysiology and for the treatment of SS patients.     

Approche moléculaire de la résistance à la méticilline de Staphylococcus aureus

Staphylococcus aureus is one of the most common species met in medical microbiology laboratories. It causes many infectious diseases, and some of them are severe. Today, it can resist to many antibiotics, that were initially fully active, such as G or A group penicillin, by producing a penicillinase. Hospital strains can also resist to M group penicillins (methicillin, oxacillin) by modifying the β-lactam target: penicillin binding protein (PBP). Indeed, these strains produce a new PBP, called PBP 2a, of which affinity for β-lactams is much lower than the one of common Staphylococcus PBP. This PBP2a is encoded by mecA gene, of which expression is under control of several regulation genes. The expression of methicillin-resistance can be homogeneous or heterogeneous. Some strains can resist to methicillin using other mechanisms (penicillinase overproduction, methicillin-specific hydrolytic enzyme, PBP modifications). Particular methods are needed for the phenotypic detection of methicillin-resistance: antibiograms on NaCl-supplemented agar or incubated at 30 °C. Molecular detection of mecA gene by PCR permits to detect that resistance on strains for which phenotypic detection has failed.     

Diagnostic moléculaire de la résistance de Mycobacterium tuberculosis aux antituberculeux

The development of new technical tools for molecular biology has modified the methods used for the identification of resistance in Mycobacterium tuberculosis. Although the proportion method generally remains the reference method, more rapid and sophisticated techniques are now available, such as PCR-SSCP analysis, LiPA hybridization and DNA sequencing. At present, PCR-SSCP analysis is no longer used in routine. The INNO-LiPA assay, which is well adapted to routine, allows the rapid determination of rifampin resistance, but is not developed yet for detecting resistance to other antimycobacterial drugs. DNA sequencing is a powerful tool for the detection of resistance to rifampin, pyrazinamide and fluoroquinolones, but not to isoniazid. However, the technique requires specific facilities which are very costly. Finally, the development of high-density oligonucleotide arrays that can be used to rapidly examine large amounts of DNA sequences could allow to simultaneously investigate a large number of mechanisms of resistance. This new approach represents a very promising alternative for the rapid analysis of genomic regions involved in drug resistance.     

Étude comparative de trois tests de dépistage des anticorps dirigés contre le virus de l'hépatite C

Three screening assays to anti-hepatitis C virus (HCV) antibody (Abs) were evaluated with two parameters, sensitivity and specificity, currently tested before routine use.The Ortho HCV 3.0 ELISA Test System Enhanced SAVe, Monolisa Anti-HCV Plus and Innotest HIV Ab IV were tested. Sensitivity was established with 5 HCV seroconversion panels from Nabi (USA) (n^o 048, 12767, SC-0010, SC-0400 and SC-0402), 3 from Bioclinical Partners (USA) (n^o 9047, 6214 and 6213) and 3 from Boston Biomedica Inc. (USA) (PHV 905, 907 and 914). The specificity was evaluated on at least 500 serum samples.With the 5 Nabi panels, the Innotest assay is the first positive on 3 panels. The 3 assays obtain similar results on the Biomedical Partners panels except on panel n^o 6214 who the positiving of the Innotest assay is 19 days delayed. Innotest and Monolisa assays are better than Ortho on the Boston Biomedica panels. Specificity of the three assays is equivalent.Innotest and Monolisa assays are the most efficient on the 11 HCV seroconversion panels tested. Ortho is the worse. Specificity is similar.