A new automated method for the determination of the Total Antioxidant Capacity (TAC) of human plasma, based on the crocin bleaching assay

BACKGROUND: Antioxidant molecules, which scavenge free radical species to prevent or delay oxidative damage of important macromolecules, membrane lipids and lipoproteins, are prevalent in plasma and other biological fluids. Among them, bilirubin, uric acid and protein thiols are the major endogenous antioxidants, while vitamins C and E, as well as a number of food-derived (poly)aromatic substances, belonging to stilbens, flavonoids and phenolic acids, are the main classes of nutritional antioxidants. Assays for total antioxidant capacity in plasma differ in their type of oxidation source, target and measurement used to detect the oxidized product. METHODS: In the present work we present an automated assay for the estimation of blood total antioxidant capacity (TAC assay), based on the crocin bleaching (oxidation) method. This method was adapted on a modern autoanalyzer, was linear over a wide range of values (0–3 mmol/L), and performed using an end point measurement. RESULTS: The TAC method presented a linear correlation with another automated commercial Total Antioxidant Status (TAS) test. Detection of the interference of different metabolites revealed a significant participation of TAC from uric acid, bilirubin, albumin, a minor interference from ascorbic acid, and no interference from hemoglobin. TAC was not modified by two freeze/thawing cycles, and was stable in samples stored at room temperature for 4 hours. K-EDTA and heparin were the best anticoagulants, while citrate decreased TAC by 20%. Reference values derived from samples of normal blood donors was 1.175 ± 0.007 mmol/L (mean ± SEM), while a diet rich in antioxidants more than doubled this value. CONCLUSIONS: The proposed TAC assay, is fully automated, stable and reliable, and could be of value in the estimation of the AC of plasma. It is further proposed to calculate the antioxidant capacity of plasma after a subtraction of all interference deriving from endogenous and/or exogenous metabolites. The antioxidant capacity of plasma thus calculated can be used as a useful indicator of the antioxidant value of foods and beverages in the daily diet

Serum Immunoglobulin Levels in Heterozygous Subjects With Immunoglobulin Heavy-chain Constant-region Gene Deletions

The immunoglobulin heavy chain constant region locus is a multigene family composed of nine genes and two pseudogenes, whose high homology is often responsible for meiotic mispairings leading to deleted and duplicated haplotypes. These rearrangements have a population frequency of about 1.5% and 4.5% respectively, with a significant difference between deletions and duplications (P < 0.001). Both positive selection of duplications or negative selection against deletions can account for this imbalance. Serum levels of IgG and IgA subclasses, of IgE, of isohemagglutinins and of IgG antibodies to tetanus toroid and pneumococcal antigens were evaluated in 11 heterozygous carriers of constant region deletions. There was no gross abnormality in serum IgG and IgA subclass levels, with the possible exception of G1-deleted individuals; furthermore, isohemagglutinins and anti-tetanus toroid and pneumococcal IgG antibodies are in the normal range, suggesting that the humoral immune response is normal in these carriers. The influence of single and multiple immunoglobulin heavy chain constant region gene deletions on the humoral response is discussed

Response to hepatitis B vaccine in a cohort of Gambian children.

In a cohort of 1000 Gambian children immunized with four doses of 10 micrograms of plasma-derived hepatitis B virus vaccine, 44 subjects (4.4%) showed no response (< 10 mIU/ml; 6 subjects) or low specific antibody response (10 to 99 mIU/ml; 38 subjects) to hepatitis B surface antigen. Serologic indices, potentially correlated with low immunologic response, were investigated in sera obtained from these children and in sex-, age- and village-matched controls who showed a normal response. The presence of circulating immune complexes in similar proportion of responding and poorly responding children together with a low prevalence of rheumatoid factors suggested that polyclonal B cell activation was not correlated with the subnormal humoral response. Concentrations of serum immunoglobulin (Ig) and IgG subclasses did not differ in the two groups. Some of the African prevalent Ig allotypes were determined, but no significant differences in the two groups were found. The humoral response to hepatitis B surface antigen did not correlate with the response to tetanus toxoid