Synthetic peptides derived from the env protein of human T-lymphotropic virus type I (HTLV-I) were used to identify the immunodominant motifs in rhesus macaques naturally infected with simian T-lymphotropic virus type I (STLV-I). Of the 13 peptides derived from the env protein of HTLV-I, Env-1(191-214) and Env-5(242-257) reacted with 81% (44/54) and 54% (29/54) of specimens from infected monkeys, respectively. A recombinant protein (MTA-I162-209) reacted with 53 of 54 (98%) STLV-I-infected serum specimens. While similar immune reactivities to Env-1 and MTA-1 were observed in both HTLV-I-infected human sera and STLV-I-infected monkey sera, the reactivity to Env-5 was significantly higher in HTLV-I-infected human sera. Differential reactivities may be attributed to the differences in the secondary structures of the STLV-I and HTLV-I envelope protein in the Env-5 region, since homologous peptide with STLV-I sequence did not result in enhanced sensitivity of anti-Env-5 antibody detection.

Amino Acid Sequence↗

PubMedDate not supplied

Isolation of cDNA clones encoding the 20K T3 glycoprotein of human T-cell receptor complex.

The complete amino acid sequence of one of the polypeptide chains of the human T3/T-cell receptor complex, the T3 glycoprotein (T3-delta-chain) of relative molecular mass 20,000, was deduced from cDNA clones derived from HPB-ALL cells and a human T-cell clone. Inspection of the 171-amino acid sequence reveals a signal peptide, a 79-amino acid extracellular domain, one transmembrane region and a 44-amino acid intracellular domain which show no sequence homology with members of the T-cell receptor/immunoglobulin/MHC multi-gene family. The T3 delta-chain is coded for by a single-copy gene the expression of which is restricted to T lymphocytes in humans and mice.

Amino Acid Sequence↗

PubMedDate not supplied

The delta- and epsilon-chains of the human T3/T-cell receptor complex are distinct polypeptides.

The T3/T-cell receptor complex on the surface of human thymus-derived lymphocytes consists of four glycoproteins: the alpha-chain of relative molecular mass (Mr) 40,000-50,000 (40-50K), the beta-chain (37-45K); the gamma-chain (25K) and the delta-chain (20K). The T3 alpha- and beta-chains have been identified as clonotypic T-cell receptors, but functionally the T3/T-cell receptor chains seem to form a single complex: monoclonal antibodies directed at the 20K T3 components are mitogenic for normal human T lymphocytes and, at higher concentrations, anti-clonotypic and anti-20K reagents block T-cell function. Recently, Zanders et al. showed that incubation of human T-helper clones with high concentrations of antigen abolishes antigen-specific proliferation and induces disappearance of T3 from the cell surface. Thus, the T3/T-cell receptor complex consists of two variable subunits, the T3 alpha- and beta-chains, which interact with antigen and the monomorphic 20K/25K T3 chains. Recently, the existence of a fifth polypeptide chain, the unglycosylated T3 epsilon-chain, has been postulated. Here we confirm that a 20K epsilon-chain does exist. The T3 epsilon-chain differs from the T3 delta-chain in primary structure as judged by N-terminal amino acid sequencing, peptide mapping and immunoblotting with anti-T3-delta and anti-T3-epsilon antibodies. Treatment with endoglycosidase F revealed two nonglycosylated T3 delta polypeptide backbone chains (16K and 14K) with identical amino termini. Together with previous pulse-chase experiments this observation suggests that the 14K T3 polypeptide is derived from the 16K T3 precursor by proteolytic processing near the C-terminus of the molecule.

Amino Acid Sequence↗

PubMedDate not supplied

Differential expression of two distinct T-cell receptors during thymocyte development.

The product of the T-cell receptor (TCR) gamma-gene has recently been found to be expressed on a subset of both peripheral cells and thymocytes. As an initial approach to understanding the role of this gamma-chain of TCR (TCR gamma) in T-cell development, we have studied the ontogeny of TCR expression at the protein level in the developing murine thymus. We show here that the first T3-associated TCR to be expressed in the developing thymus is a disulphide-linked heterodimer composed of a gamma-chain of relative molecular mass 35,000 (Mr 35K) and a 45K partner (termed TCR delta). This TCR gamma delta is first detected approximately two days before the appearance of cell-surface TCR alpha beta heterodimers. We report that N-glycosidase digestions reveal that all of the gamma-protein expressed on fetal thymocytes, as in adult CD4-8-(L3T4-, Lyt2-) thymocytes, bear N-linked carbohydrate side chains. The major gamma-gene transcribed in mature, alpha beta-bearing T cells (V gamma 1.2C gamma 2)encodes no N-linked glycosylation site so these results suggest that the fetal gamma delta receptor defines a distinct T-cell lineage whose development in the thymus precedes classical alpha beta-bearing cells.

Animals↗

PubMedDate not supplied

A novel population of T-cell receptor alpha beta-bearing thymocytes which predominantly expresses a single V beta gene family.

Recent studies have demonstrated that CD3 is expressed on a subset of thymocytes with a CD4-CD8- (double negative) phenotype. At least some of these cells bear the CD3-associated gamma delta T-cell receptor (TCR gamma delta). Here we describe a second subset of double negative thymocytes which expresses CD3-associated alpha beta receptors (TCR alpha beta). Surprisingly, these cells express predominantly the products of a single V beta gene family (V beta 8). These CD4-CD8-, TCR alpha beta+ cells appear relatively late in ontogeny (between birth and day 5 of life) and thus are unlikely to be the precursors to the TCR alpha beta-bearing cells (CD4+CD8- and CD4-CD8+) already present at birth. They can be selectively expanded in vitro by stimulation with a monoclonal antibody to V beta 8 (F23.1) in the presence of interleukin I (IL-1). We propose that this cell type is a unique T-cell population distinguishable from typical TCR alpha beta+ T cells by its CD4-CD8- phenotype and a restricted TCR V beta repertoire. Analysis of the unique phenotype of these cells suggests that they may represent the normal counterpart of the defective CD4-CD8- T cells found in the lpr autoimmune mouse.

Animals↗

PubMedDate not supplied

Antibodies to streptococcal carbohydrate: substitutes for the myeloma proteins.

Antibodies to streptococcal carbohydrates have been employed in a number of ways as substitutes for the myeloma proteins in studies of the structures of antibody molecules and the development of the immune response. This review concentrates on the chemical nature of the streptococcal polysaccharides and on structural studies of the variable regions of the light chains of rabbit anitbodies to the group A-variant polysaccharide produced by hyperimmunization. The chemistry of the group A-variant polysaccharide has now been clarified, and this information has explained the frequently reported difficulty in the preparation of precipitating antisera to this antigen. The group A-variant vaccine is a potent antigen, but the bulk of the antibody is nonprecipitating because it is directed against the noreducing terminal sugar of the nonbranched rhamnose polymer. Chemical studies of the light chains of homogeneous rabbit antibodies reveal two hypervariable regions and a J sequence that joins the variable region to the constant region. Although the precise topographic highlights of the antigen-binding site hae yet to be determined, these structural studies have extended our knowledge of the structure and diversity of antibody molecules.

Animals↗

PubMedDate not supplied

Synthetic peptides from P. falciparum sexual stage 25-kDa protein induce antibodies that react with the native protein: the role of IL-2 and conformational structure on immunogenicity of Pfs25.

To identify B-cell epitopes of the Plasmodium falciparum 25-kDa ookinete protein, Pfs25, 41 overlapping synthetic peptides spanning the entire length of the protein were used individually to immunize CAF1 (F1 hybrid of BALB/c female and A/J male) mice. Antipeptide sera were tested for reactivity to live intact zygote/early ookinete (post-fertilization stage) by immunofluorescence, and by Western blot analysis under nonreducing and reducing conditions, immunoprecipitation of 35S-cysteine-labeled antigen, and ELISA using a vaccinia recombinant Pfs25 antigen. Fourteen B-cell epitopes were identified. These peptides were immunogenic only when administered with high-dose recombinant interleukin-2. Antibodies to 11 peptides recognized only the native conformational structure, one peptide induced antibodies that recognized both reduced and native protein, and two other peptides, after primary immunization, made antibodies to denatured Pfs25, but after boosting the antibodies reacted to both denatured and native Pfs25. Anti-sera to peptides in the first (peptide 7) and fourth (peptide 34) epidermal growth factor-like domains of Pfs25 reacted most strongly with zygotes/ookinetes by immunofluorescence assay. The antibodies elicited by immunization with peptide 34 suppressed infectivity of the parasite to mosquitoes. We further observed that the secondary structure of Pfs25 may be important for immunogenicity because monoclonal antibodies (MAbs) 1C7 and 1D2, both transmission-blocking MAbs, protected enzyme cleavage sites in Pfs25 from proteolysis, suggesting that discontinuous segments of Pfs25 may come together to form immunogenic epitopic sites. Thus, definition of B- and T-cell epitopes may be required to construct a Pfs25 vaccine for optimum immunogenicity.

Amino Acid Sequence↗