Evelyne Jouvin-Marche

Regulation of TCR α and β gene allelic exclusion during T-cell development

Abstract Early in their development, most T cells become committed to the expression of one, and only one, TCR αβ combination. How do T cells achieve this TCR allelic exclusion? This article discusses the configuration and expression of TCR α and β genes in mature T-cell lines and TCR αβ transgenic mice, and proposes three nonexclusive models to account for the significant occurrence of T cells with two productive α gene rearrangements.

Quantitative and Qualitative Changes in V-J α Rearrangements During Mouse Thymocytes Differentiation Implication For a Limited T Cell Receptor α Chain Repertoire

Knowledge of the complete nucleotide sequence of the mouse TCRAD locus allows an accurate determination V-J rearrangement status. Using multiplex genomic PCR assays and real time PCR analysis, we report a comprehensive and systematic analysis of the V-J recombination of TCR α chain in normal mouse thymocytes during development. These respective qualitative and quantitative approaches give rise to four major points describing the control of gene rearrangements. (a) The V-J recombination pattern is not random during ontogeny and generates a limited TCR α repertoire; (b) V-J rearrangement control is intrinsic to the thymus; (c) each V gene rearranges to a set of contiguous J segments with a gaussian-like frequency; (d) there are more rearrangements involving V genes at the 3′ side than 5′ end of V region. Taken together, this reflects a preferential association of V and J gene segments according to their respective positions in the locus, indicating that accessibility of both V and J regions is coordinately regulated, but in different ways. These results provide a new insight into TCR α repertoire size and suggest a scenario for V usage during differentiation.

Vβ17 gene polymorphism in wild-derived mouse strains: Two amino acid substitutions in the Vβ17 region greatly alter T cell receptor specificity

Abstract Of 41 wild-derived mouse strains analyzed, 14 contained T cells bearing Vβ17 receptors in splte of the concomitant expression of I-E antigens. Reciprocal F1 and F2 hybrids of one of these strains, PWK, with laboratory strains revealed different patterns of Vβ17 T cell deletions from those observed with Vβ17 T cells from SJL, implying that the two Vβ17 regions are associated with recognition of distinct superantigens. The structures of the Vβ17 alleles differ by two amino acid substitutions, which lie together in an area distant from the predicted site of T cell receptor interaction with peptide-MHC complexes but overlapping with that implicated in Vβ8.2 recognition of Mls-1 superantigen. This demonstrates that the self-superantigen leading to Vβ17 T cell deletion varies with the allele of the receptor gene and confirms that T cell deletions by such ligands involve interactions with a region of the Vβ domain that is distinct from the conventional combining site.

The mouse Igh-1a and Igh-1b H chain constant regions are derived from two distinct isotypic genes.

Genetic and structural analyses of the mouse genes encoding constant region of immunoglobulin subclasses (Igh-C) have shown that recombination is rare within this cluster which is inherited as a set designated the Igh haplotype. Recent molecular analyses have demonstrated that either DNA exchanges or gene duplications have probably occurred during the evolution of this set of genes. In order to assess the generality of the duplication processes, the presence and expression of two allelic forms of the Igh-1 (γ2a) gene (Igh-1a and Igh-1b) were examined in a large panel of wild mice belonging to Mus musculus domesticus and Mus musculus musculus species. Our data indicate that certain M. m. domesticus animals and most animals in the M. m. musculus group coexpress the two allelic forms of Igh-1. Moreover, genetic studies show that these two immunoglobulin types are encoded by tandemly arranged genes. We propose that wild mice, from which laboratory mice are derived, carry three isotypic γ2 genes (Igh-1a, Igh-1b, Igh-3), and these have given rise to the two isotypes seen in laboratory strains by a deletion/insertion mechanism.

Complexity, polymorphism, and recombination of mouse T-cell receptor α gene families

Genomic DNA from a large panel of inbred strains of mice were hybridized sequentially with 15 Vα, 2 Vδ, 1 Cα, and 1 Cδ probes. Most of the Vα probes detected a high degree of plymorphism and have allowed the definition of five mouse T-cell receptor α (Tcrα) haplotypes. One of these haplotypes (Tcrαe) appears to arise from a recombination between theTcrαb andTcrαa haplotypes, the latter being the most frequently found in the conventional inbred strains. This recombination event clearly indicates that the members of at least 11 Vα subfamilies are not closely linked but highly interspersed with one another on chromosome 14.

p53-dependent and p53-independent pathways for radiation-induced immature thymocyte differentiation

The pre-T-cell receptor (TCR) delivers essential survival/differentiation signals to the developing thymocytes. Severe combined immunodeficient (SCID) and recombination-activating gene (RAG)-deficient mice are unable to assemble antigen receptor genes, and therefore cannot express a pre-TCR. Consequently, T lymphocyte differentiation is arrested at an early stage in the thymus of these animals, and immature thymocytes are eliminated through apoptotic processes. This maturation arrest can be relieved and thymocyte differentiation rescued after the exposure of these mice to whole-body γ-irradiation. Whereas the promotion of immature thymocyte survival/differentiation was shown to require p53 activity in irradiated SCID mice, it was suggested, on the other hand, that p53 activation prevents immature thymocytes survival/differentiation in irradiated RAG-deficient mice. However, SCID mice have impaired responses to ionizing radiation. In this paper, we analysed p53 requirement in radiation-induced thymocyte differentiation in CD3ɛΔ5/Δ5 mice, where pre-TCR deficiency also results in an early block of lymphocyte development. Our results show at the cellular and molecular levels that, in this DNA repair-proficient model, irradiation-induced thymocyte differentiation proceeds either by a p53-dependent or by a p53-independent pathway, which differ in their sensitivity to the radiation dose delivered.

New T-cell receptor gamma haplotypes in wild mice and evidence for limited Tcrg-V gene polymorphism

Tcrg gene polymorphism was investigated by Southern blot analysis on a panel of laboratory and wild mouse strains using a set of probes which identify all known Tcrg-V and -C genes. Only three haplotypes are found in laboratory mice: gA, gB, and gC which are represented by BALB/c, AKR, and DBA/2 prototypes respectively. gA and gC haplotypes are the most frequent among laboratory mice whereas gB is poorly represented. Seven new haplotypes are described among 23 wild mice corresponding to four Mus musculus subspecies (Mus mus domesticus, castaneus, musculus, and molossinus). However, only a few new alleles of individual genes are observed. Tcrg-V genes located at the 5′ end of the Tcrg locus (V7 and V4) appear to be nonpolymorphic whereas two Tcrg-V3,-V5,-V6,-C4 and three Tcr-V1,-V2,-C1,-C2, and -C3 specific restriction fragment length polymorphisms are detected. These results indicate a relatively high degree of conservation of Tcrg genes as compared to other members of the immunoglobulin (Ig) gene family and might be related to the specificity and function of γδ T cells. Several of the new haplotypes described here result from point mutations in noncoding Tcrg-V or -C gene-flanking regions. Recombinations may have also participated in the evolution of the Tcrg locus. Finally, these new Tcrg haplotypes are unequally distributed among the four M. m. subspecies and support the idea that the gA and gC haplotypes found in laboratory mice are inherited from M. m. domesticus whereas gB might originated from asian subspecies (castaneus, musculus or molossinus).

Molecular characterization of the variable regions of a mouse polyreactive IgG2b antibody with rheumatoid factor activity

The complete nucleotide sequences of heavy and light chains of a mouse polyreactive IgG2b antibody were determined. This antibody, obtained after primary immunization of BALB/c mice with human lymphoblastoid cells, possess anti-HLA-DR and anti-rheumatoid factor activities and reacts with various self and nonself antigens. The VL and VH segments were found to belong to the VK8 and VH7183 families, respectively. The VH segment shared a high percentage of sequence similarity (95%) with previously described germline genes. The VK segment had 98.9% of sequence similarity with a consensus sequence VK8 of antibodies with anti-phosphorylcholine activity. Furthermore, the framework regions 2 and 3 of the VL segment were very similar to the framework regions 2 and 3 of other antibodies known to possess rheumatoid factor activity. We postulate that during immunization, the presence of HLA-DR antigens selects precursors having configurations similar to that of the germline, and induces some somatic mutations that do not significantly affect antibody polyreactivity.

Sex Differences in Spontaneous Degranulation Activity of Intrahepatic Natural Killer Cells during Chronic Hepatitis B: Association with Estradiol Levels

Major sex differences are observed in the prevalence, intensity, and severity of hepatitis B virus (HBV) infection. Here, we investigated degranulation activity of circulating and intrahepatic natural killer (NK) cells from HBV and HCV chronically infected patients before any treatment (n = 125). The frequency of CD107+ NK cells in the female liver was significantly higher compared to that in males during chronic HBV infection (p = 0.002) and correlated with the plasma levels of estradiol (correlation coefficient r = 0.634; p < 0.0001). Our results clearly show sex differences in degranulation activity of intrahepatic NK cells of HBV-infected patients. This probably contributes to the ability of females to better deal with HBV disease.

Modeling the Rearrangements of Genes Encoding Immune Receptors. Toward a Prediction Tool of Immune Specificity

This paper describes a general random mechanism of vanishing the central part of a concatenated chain made of characters in an alphabet of cardinal 4. This mechanism allows to obtain chains shorter than the initial one with some constraint for the start and the end of the resulting chain. An application in immunology of this chain shortening procedure will be proposed, describing the genesis of new functional genes from the TCRAD locus on the chromosome 14 in mice and humans encoding immune receptors.