Tracy, Russell P.

Background —T cells are implicated in atherosclerosis, but little is known about the genetic control or molecular pathways, especially under conditions of mild hypercholesterolemia. Methods and Results —BALB/c mice, making a CD4+ Th2 (IL-4+) cell response, express both MHC class II antigens (IA d , IE d ) and are atherosclerosis-resistant. C57Bl/6 mice produce a CD4+ Th1 (interferon [IFN]γ+) response, express IA b but no IE, and are atherosclerosis-prone. To evaluate T helper–cell phenotype in fatty streak formation, wild-type C57Bl/6 mice (IA b +IE−) and transgenic mice, either AB o , IA b −IE−; ABEα, IA−IE k +; or Bl.Tg.Eα, IA b +IE k +, were fed a high-cholesterol diet for 16 weeks and evaluated histomorphometrically for aortic lesions. Lesion size in AB o , ABEα, and Bl.Tg.Eα strains was decreased by 54%, 79%, and 82%, respectively, compared with wild-type, correlating with decreased Th1 and increased Th2 expression and suggesting that T helper–cell phenotype is important in fatty lesion development. Decreasing Th1 cells by antibodies (α-CD4) or cytokines (IL-4) also caused ≥80% reductions in lesion size. Immunohistology revealed IFN-γ, but not IL-4, colocalized with activated macrophages. Confirming these findings in a different mouse strain, BALB/c Stat 6 knockout mice (Th2 cell–deficient) developed aortic lesions comparable to C57Bl/6 mice on the same diet. Conclusions —In mildly hypercholesterolemic C57Bl/6 mice, presence of IA b and absence of IE regulated CD4+ T helper–cell phenotype; fatty lesions were proportional to IFNγ+ Th1 cells in both C57Bl/6 and BALB/c strains. IFN-γ may participate through macrophage activation, whereas IL-4 may act to limit Th1-cell response.

Abstract We have compared two assays for osteocalcin (BGP, bone gla protein), one based on a monoclonal antibody, the other based on a polyclonal serum, in an effort to better understand the factors that contribute to the wide variation reported for osteocalcin normal ranges. The two assays compared well using serum samples, with a correlation coefficient of 0.9071 (n = 48). However, the monoclonal antibody assay returns values increased over the polyclonal assay by approximately 1.5-fold. Gel permeation studies indicate that these larger values are due primarily to increased reactivity in the monoclonal assay with high- and low-molecular-weight forms of osteocalcin in plasma; both assays give similar reactions to intact osteocalcin. Analysis of samples from individuals with increased bone resorption due to parathyroid hormone administration reveals that the decrease seen in osteocalcin values after hormone infusion occurs primarily in the fraction that corresponds to intact osteocalcin. During the course of these studies, we re-evaluated the extinction coefficient for osteocalcin, arriving at the value E = 1.33 mg/ml−1, cm−1. We also observed a significant negative interference in both assays (and a commercial assay) caused by hemolysis. This interference is due to proteolysis of osteocalcin by enzymatic activity released from the lysed red cells.