Background The long chain omega-3 fatty acids (n-3 fatty acids) that derive from fish (eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA)) are associated with a reduced risk of cardiovascular and other chronic disease. However, studying associations between EPA and DHA intake and disease rigorously requires a valid biomarker of dietary intake, and measuring tissue fatty acid levels directly is expensive and time consuming. Objective Because the nitrogen stable isotope ratio (15N/14N, expressed as δ15N) is elevated in fish, we investigated whether δ15N can provide a valid, alternative biomarker for EPA and DHA intake. Design We examined the relationship between red blood cell (RBC) δ15N and RBC EPA and DHA in a community-based sample of 496 Yup'ik Eskimos with widely varying intake of n-3 fatty acids. We also assessed the correlation between δ15N and EPA and DHA dietary intake, based on a 24-hour dietary recall and a 3-day food record completed by a subset of 221 participants. Results RBC δ15N was strongly correlated with RBC EPA and DHA (r = 0.83 and 0.75 respectively). These correlations differed only modestly by sex and age class. RBC δ15N also correlated with dietary EPA and DHA intake (r = 0.47 and 0.46, respectively), and did not differ by sex and age. Conclusions These results strongly support the validity of RBC δ15N as a biomarker of EPA and DHA intake. Because analysis of RBC δ15N is rapid and inexpensive, it could facilitate wide scale assessment of EPA and DHA intake for clinical and epidemiological studies.

Fifty-three patients with severe aplastic anaemia were admitted to this hospital between January 1976 and June 1980, of whom three arrived in terminal condition and died before treatment for their basic disease could be given. Thus 50 patients were treated and evaluated in a prospective study according to one protocol. Eighteen patients with an HLA-identical sibling underwent bonemarrow transplantation with the aim of achieving haematopoietic chimerism. Thirty-two patients without an HLA-identical sibling were given antilymphocyte globulin with or without an infusion of HLA-haplotypeidentical marrow. All these 32 patients received low-dose androgens after the procedure. In the first group eight

We have studied the repopulation of the T-cell compartment in 27 patients transplanted with bone marrow from an (HLA)-identical sibling. Significant differences were found between recipients of unmanipulated and T-cell depleted grafts. Analysis of the T cells by a method based on amplification of minisatellite DNA regions showed that without depletion > 99.9% of the clones responding to a mitogenic stimulus after transplantation were of donor origin. In contrast, when the graft had been depleted with Campath-1M plus complement, a significant part of the T cells cloned during the first weeks after transplantation comprised of recipient T cells that had survived the preconditioning. This mixed population of low numbers donor and recipient T cells (19 +/- 31/mm3 at day 14) expanded rapidly (predominantly CD8+ T cells) during the first 2 months, without a significant change of the ratio of recipient/donor T cells. In 11 of 17 evaluable patients a late wave ( > 9 months) of donor T cells occurred. As a consequence, T-cell chimerism changed in favor of donor T cells and the CD4/CD8 ratio that had been reversed ( < 0.5) after the first expansion, normalized (1.5 +/- 0.51). Analysis of the T-cell receptor repertoire showed that in recipients of a T-cell depleted graft, the recipient as well as the donor T cells that repopulated the peripheral T-cell pool during the first month, were the progeny of a limited number of precursors. Because without depletion, when larger numbers of donor T cells had been cotransfused with the marrow, the repertoire was much more diverse, these data show that immediately after transplantation, the peripheral pool is repopulated primarily through expansion of circulating T cells.