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Biomedical subjects

N Green

Publications and source records attributed to N Green.

126 records · Page 7Linked to original sources
PubMedDate not supplied

Tolerance of T-cell clones is associated with membrane antigen changes.

It is possible to regulate the activity of human influenza virus specific helper T-cell clones either by high concentrations of antigen or by anti-idiotypic suppressor T cells. In the absence of accessory cells, the appropriate peptide antigen recognized by the clones induces specific unresponsiveness. This phenomenon, however, is not the result of cytolysis as responsiveness to IL-2 remained unaltered. This suggests that high-dose immunological tolerance need not involve suppressor T cells, and that peptide antigens can interact directly with the T-cell surface. As recent reports suggest that the T-cell surface antigen T3 is involved in the triggering of T lymphocytes and possibly in antigen recognition we have investigated the expression of T3 and other cell surface antigens following the induction of T-cell tolerance. We report here that when a T-cell clone is exposed to a tolerizing concentration of the appropriate peptide antigen, surface T3 antigen is lost in a dose-dependent manner. As loss of surface T3 induced by anti-T3 antibody also results in unresponsiveness to antigen, we conclude that T3 is involved in the process of T-cell triggering by antigen.

Antibodies, Monoclonal↗
PubMedDate not supplied

Mimicking the alloantigenicity of proteins with chemically synthesized peptides differing in single amino acids.

Recent studies have shown that short chemically synthesized peptides very often induce antibodies which react with the cognate sequence in the intact folded protein. Since such antibodies react with known regions of proteins, they are of predetermined specificity and offer a precision not previously possible with immunological probes. A basic concept emerging from the use of such antibodies in viral systems is that the differential immunogenicity of closely related proteins can be mimicked by short peptides which span the regions of sequence variation. To generalize this concept, we have studied the two Thy-1 proteins which vary by only a single amino acid. Chemically synthesized peptides differing in only one out of 19 amino acids were able to induce allospecific antisera. Thus, single amino acid changes have similar effects on the immunogenicity of proteins and small peptides, even though the latter are free from constraints provided by neighbouring structures in the tertiary configuration of the intact folded proteins.

Amino Acid Sequence↗
PubMedDate not supplied

Estimation of the caries-related risk associated with infant formulas.

PURPOSE: Baby bottle tooth decay (BBTD) affects 6% of children under three years of age and is associated with inappropriate bottle use. The objective of this study was to estimate the caries-related risk associated with 26 infant formulas and whole milk. METHODS: First, the plaque pH of adult volunteers was monitored before and after an oral rinse with infant formula to determine the minimum pH obtained in response to each formula. Second, Streptococcus sobrinus 6715 was cultured in each infant formula, and the increase in the number of colony forming units was measured. Third, each infant formula was incubated with powdered enamel and the solubility of enamel mineral was calculated in the absence of bacteria. Fourth, each formula was mixed with standardized concentrations of acid to determine the buffering capabilities. Finally, enamel windows were created on extracted permanent molars and exfoliated primary incisor crowns that were then colonized with mutans streptococci and incubated with infant formula. Caries was assessed visually and radiographically for 18 weeks. The length of time required for the development of enamel caries, dentinal caries and pulpal involvement was recorded. RESULTS: One-way or two-way ANOVA of these five assays demonstrated that 1. Plaque pH varied in response to oral rinsing with infant formula and most formulas did have the ability to reduce the pH significantly below the pH obtained after rinsing with water 2. Some infant formulas supported significant bacterial growth 3. Enamel mineral was dissolved by incubation with certain infant formula 4. The buffer capacity varied among the infant formulas tested 5. The length of time required for caries to reach dentin or pulp differed for the formulas, with some formulas causing dentinal caries by 3.4 weeks and pulpal involvement by 7.2 weeks.

Acids↗