Annales d'immunologie最新文献

The HLA complex encodes several sets of membrane glycoproteins with extensive genetic, functional and structural polymorphism. The HLA-D region and its products, the HLA-DR antigens, are central in immune phenomena. They control the mixed lymphocyte reaction, the graft versus host reaction in vivo and cell/cell interactions involved in immune responses. Monoclonal anti HLA-DR antigens have been used to investigate the expression and synthesis of human Ia antigens on B and active T lymphocytes and macrophages. They were subsequently used in structural studies of HLA-DR antigens analysed by two-dimensional gel electrophoresis. The HLA-DR antigens are composed of a bimolecular complex of two non-covalently linked subunits: a 34,000 dalton alpha chain and a 29,000 dalton beta chain. Glycosylation steps and molecular maturation include the addition of oligosaccharides and sialic acid residues to the native polypeptide chain. The structural polymorphism which correlates with the serologically defined HLA-DR determinants is localized on the beta chain and is of polypeptidic origin. A third component of the HLA-DR antigen is described: the 31,000-dalton "invariant" chain. Its peptide composition, glycosylation pattern and expression are reported. Homologies of HLA-DR antigens with the mouse Ia antigens are discussed. Structural studies of the human Ia system are important in dissecting the functional role of the different epitopes of the HLA-DR molecules.

This review summarizes some of the recent observations regarding the active T-rosette assay. This test, performed under suboptimal technical conditions, identifies a subpopulation of T lymphocytes with high-avidity receptors for sheep red blood cells. They are Ia-positive but appear to lack an Fc receptor. They can be either OKT4-positive or OKT8-positive. Isolated active T-rosette populations are capable of recognizing and killing allogeneic cells and they also modulate B-cell immunoglobulin production. They are directly correlated in vivo with specific cutaneous reactivity to an antigen. More interestingly, the percentage of active rosettes specifically increases in vitro after one hour of incubation with soluble or cellular antigens. This test fully correlates with the lymphocyte stimulation test. In the case of human mixed lymphocyte culture, the increase in active T rosettes is due to antigenic differences in the HLA D-DR region. The neoformation of active T rosettes is due to the early release of a rosetting factor. Drugs which are able to modulate T-cell functions, such as thymosin, transfer factor, isoprinosine and NPT-15392, also increase the percentage of active T rosettes. Therefore, the newly formed active T rosettes appear to be an early marker for lymphocyte activation.

In this brief review the properties of some lymphocyte surface antigens are described. The biochemical characteristic and the cell distribution of the Lyt antigen are analysed. A peculiar consideration has also been devoted to a new family of T-cell alloantigens linked to Igh-1 and recently described by Owen et al. The respective role of T helper and T suppressor cells in the regulation of isotype expression is discussed in the light of data recently obtained in the laboratory.

Poly(A+) RNA have been extracted from the human adult cell lines Raji and D98 (HeLa) and from the teratocarcinoma-derived cell lines TeraI and PA1. The TeraI cell line expresses many markers in common with undifferentiated mouse embryonal carcinoma cells and has been previously shown to be less differentiated than PA1. Only small amounts of poly(A+) RNA extracted from TeraI were found to hybridize with human HLA and beta 2-microglobulin (beta 2m) cDNA probes, while poly(A+) RNA from PA1 and the two other adult cell lines exhibited intense hybridization to these two probes. Our results correlate with the differentiation status of the various cell lines as defined by serological and biochemical analysis and suggest that HLA and beta 2m gene expression is mainly controlled at the transcriptional level.

The aim of this paper was to review the action of the receptors for the Fc portion of Ig on the polyclonal activation of human B lymphocytes. The IgG Fc fragments were shown to be digested by monocytes into peptides which triggered B-cell differentiation and the release of a T-cell replacing factor termed (Fc)TRF. In the presence of PWM and monocytes, unbound aggregated IgG suppressed B-cell differentiation into Ig-synthesizing cells. This suppression was not isotype-specific. After having bound aggregated IgG, T cells were able to display an isotype-restricted suppression of B-cell differentiation induced by PWM. Finally, soluble Fc gamma R released from T or B lymphocytes or neutrophils were found to inhibit both the synthesis of IgG and the maturation of B cells into IgM or Ig A-secreting cells.

Two types of antibodies have been prepared against beta-adrenergic receptors: (1) antibodies against receptor, purified from turkey erythrocyte membranes by affinity chromatography on alprenolol sepharose, and (2) antiidiotypic antibodies raised against the anti-alprenolol immunoglobulins. Both types of antibodies specifically bind to cells which possess beta-adrenergic receptor and mimick the biological effect of the catecholamine hormone: they stimulate basal adenylate-cyclase and enhance adenylate-cyclase activation by catecholamines. The antiidiotypic antibodies only compete with (--)-3H-dihydroalprenolol for binding to the beta-adrenergic receptors on purified turkey erythrocyte membranes. The use of these antibodies as tools for the study of the mechanism of the beta-adrenergic receptor-cyclase complex is discussed.

The protein-blotting technique has been tested as a mean to study the expression of idiotypic determinants. A monoclonal BALB/c antipoly (Glu60-Ala30-Tyr10) GAT antibody (G5) was caused to migrate on SDS gel and transferred to a nitrocellulose filter. To facilitate the renaturation of the idiotypic determinants, the blotted proteins were incubated in NP40 buffer, immediately after the transfer. The ability of two anti-idiotypic sera to detect two defined idiotypic specificities of the blotted G5 molecules was investigated. When G5 was electrophoresed on SDS gel under non-reducing conditions, a specific detection of two idiotypic specificities of the G5-blotted molecules was obtained. On the other hand, when G5 was migrated under reducing conditions, none of the two antiidiotypic sera gave a staining of the heavy and the light chains. This result indicates that molecules expressing conformational idiotypic determinants can be detected by protein-blotting technique after migration on SDS gel. Moreover, this suggests the possible interest of this technique to analyse non-antibody molecules bearing idiotypic determinants.