C. de Préval

Substance P enhances cytokine-induced vascular cell adhesion molecule-1 (VCAM-1) expression on cultured rheumatoid fibroblast-like synoviocytes

Rheumatoid arthritis (RA) is an autoimmune disease characterized by inflammation of the synovial membrane of multiple joints. This inflammatory microenvironment allows fibroblast‐like synoviocytes (FLS) to express or enhance several adhesion or costimulatory molecules. This phenotypic shift, under proinflammatory cytokines, seems to be related to functional consequences for antigen presentation to T cells. The sensory neuropeptide substance P (SP), present at high levels, is able to act on FLS proliferation and enzyme secretion. These data led us to investigate whether SP could also provoke a phenotypic change of FLS. Using flow cytometry and a three‐step cellular ELISA method, we determined whether SP has an influence on the expression of MHC class II, intercellular adhesion molecule‐1 (ICAM‐1), VCAM‐1, LFA‐3, CD40, B7.1 or B7.2 molecules on RA FLS incubated with interferon‐gamma (IFN‐γ) or IL‐1β or tumour necrosis factor‐alpha (TNF‐α) with or without SP. Our results indicate that SP potentiates the effect of proinflammatory cytokines on the expression of VCAM‐1 on RA FLS. We verified the presence of specific SP (NK1) receptor mRNA. Using reverse transcription‐polymerase chain reaction, we showed that RA FLS of patients express NK1 receptor mRNA. These results suggest that SP increase of cytokine‐induced VCAM‐1 expression acts via this specific SP receptor. Thus, during chronic inflammation RA FLS are at the interface between the immune and the nervous systems.

Monoclonal antibodies reveal three types of idiotypic determinants on MOPC 173: H-L-specific private and public idiotopes, anD VH-specific public idiotope(s)

Monoclonal anti-idiotypic antibodies against the IgG2a, K myeloma protein MOPC 173 were raised with A/J- and CBA-immune B-cells. The specificity of the antibodies was studied by hemagglutination and inhibition of a radioimmunoassay (RIA). A series of myeloma proteins, their H- and L-chains, free or reassociated in various combinations, were used as inhibitors. The RIA patterns allow recognition of three types of idiotypic determinants: private conformational idiotope(s), a public conformational idiotope, and public VH-determinant(s). Strain distribution of the public determinant was studied. A tentative correlation between amino acid positions and Id determinants is discussed.

Promiscuous and specific binding of HIV peptides to HLA-DR1 and DR103. Impact on T-cell repertoire of nonimmunized individuals.

The binding of immunogenic peptides to DR molecules is influenced by residues that point into the peptide-binding groove. The T-cell response toward a peptide complexed to an MHC molecule depends on the presence of a sufficient number of T cells reactive with peptide-MHC complex on the surface of APCs. From 96 overlapping HIV peptides, we have selected 11 that show a significant binding to either DR1, DR103, or both. These two DR molecules are identical except for three amino acids at positions 67, 70, and 71 on the beta chain. Peptide-specific T-cell lines and clones were generated with cells from nonimmunized donors homozygous for DR1 or DR103 by using either individual peptides or peptide pools for the in vitro priming. Three of the peptides induced T-cell-specific proliferative response in both individuals, and these peptides were not among those with highest affinity. Most of the peptides induced strong responses against autologous APCs. This might reflect cross-reactivity between HIV and self-peptides. Definition of peptides that both show promiscuous binding to DR and elicit a strong T-cell response is important for design of efficient synthetic vaccines.

Polymorphism Study of Tcr α and γ Genes in Insulin Dependent Diabetes Mellitus (Iddm) Multiplex Families

T-cell receptor (TCR)α and γ genes polymorphisms were analysed by Restriction Fragment Length Polymorphism (RFLP) in 10 Insulin Dependent Diabetes Mellitus (IDDM) multiplex families. TCRα and γ alleles distribution does not significantly differ between affected and non affected children. Furthermore there was no excess of Cα or V γallele sharing in affected sib pairs. Therefore the T-cell receptor α and γ chain alleles studied do not seem to affect IDDM susceptibility per se.

Localisation of the recombination points in a family with two DR/DP recombinations

In a family with a maternal DR/GLO recombination, cellular DP typing showed it to be located between DR and DP. RFLP studies done during the 9th international histocompatibility workshop gave anomalous segregation patterns of DPA and DPB bands that could be interpreted as being due to a second, paternal DR/DP recombination. This assumption was confirmed later by PCR-SSO typing. A more precise mapping has been done by new markers showing the maternal recombination to be within the TAP2 locus and the paternal recombination to be between DQB1 and DQB3. This supports earlier suggestions of a hot spot of recombination in the TAP region. The recombinations involve parental haplotypes that presently show DR/DP linkage disequilibrium in the French population and it is proposed that DR/DP recombinations occur randomly while B/DR recombinations preferentially occur on haplotypes without strong linkage disequilibrium. Existing DR/DP linkage disequilibria in a given population will thus be broken down with time. The mixed lymphocyte culture response towards an isolated DP difference was tested in this and another DR/DP recombinant family. It showed that an alloresponse towards DP may be highly variable and this suggests that it might be important to define the rules for the strength of this reaction and the possible implications for allotransplantation.

Different DQw2 Are Associated with DR3 and DR7 as Revealed by RFLP Analysis

HLA-DQ antigens were first characterized by serologic assays. Three types of HLA-DQ alloantigens have been defined: HLA-DQw1, -DQw2, -DQw3. At the genomic level, two genes encoding the α chain (αDQ, αDX) and the β chain (βDQ, βDX) have been identified within the HLA DQ region of the major histocompatibility complex. The DQw2 specificity is in strong linkage disequilibrium with HLA-DR3 and -DR7 alleles. Recently, biochemical studies and RFLP analysis allowed the split of HLA-DQw1 and DQw3 types in several subgroups (1). Immunoprecipitation and two-dimensional gel analysis revealed a βDQ chain polymorphism between DQw2 molecules isolated either from cells bearing DR3 or DR7, DQw2 haplotypes.