Anti-CD48 Monoclonal antibody, clone IN59-2 [PE/Cy7®]

Objective-Recently, we demonstrated that scavenger receptor type BI (SR-BI), a high-density lipoprotein (HDL) receptor, was expressed on murine hematopoietic stem/progenitor cells (HSPC) and infusion of reconstituted HDL and purified human apolipoprotein A-I (apoA-I) suppressed HSPC proliferation. We hypothesized that SR-B1 expression is required for the observed antiproliferative effects of HDL on HSPC. Approach and Results-SR-BI-deficient (SR-BI-/-) mice and wild-type controls were fed on chow or high-fat diet (HFD) for 8 to 10 weeks. Under chow diet, a significant increase in Lin(-) Sca1(+) cKit(+) cells (LSK cells, so-called HSPC) was found in the bone marrow of SR-BI-/- mice when compared with wild-type mice. HFD induced a further expansion of CD150(+)CD48(-) LSK cells (HSC), HSPC, and granulocyte monocyte progenitors in SR-BI-/- mice. Injection of reactive oxygen species inhibitor N-acetylcysteine attenuated HFD-induced HSPC expansion, leukocytosis, and atherosclerosis in SR-BI-/- mice. ApoA-I infusion inhibited HSPC cell proliferation, Akt phosphorylation and reactive oxygen species production in HSPC and plaque progression in low-density lipoprotein receptor knockout (LDLr-/-) apoA-I-/- mice on HFD but had no effect on SR-BI-/- mice on HFD. Transplantation of SR-BI-/- bone marrow cells into irradiated LDLr-/- recipients resulted in enhanced white blood cells reconstitution, inflammatory cell production, and plaque development. In patients with coronary heart disease, HDL levels were negatively correlated with white blood cells count and HSPC frequency in the peripheral blood. By flow cytometry, SR-BI expression was detected on human HSPC. Conclusions-SR-BI plays a critical role in the HDL-mediated regulation HSPC proliferation and differentiation, which is associated with atherosclerosis progression.

We previously reported that rat spleen T-cells and peripheral red blood cells that are deficient in glycosylphosphatidylinositol (GPI) synthesis [presumed mutants for the phosphatidylinositol glycon complementation group A gene (Pig-A)] could be detected by flow cytometry (FCM) as cells negative for GPI-linked markers (CD48 and CD59, respectively). To establish this procedure as a rapid in vivo gene mutation assay, we have examined the Pig-A gene of GPI-deficient rat spleen T-cells for DNA sequence alterations. Splenocytes were isolated from male F344 rats, primed with ionomycin and phorbol-12-myristate-13-acetate, and seeded at limiting-dilution into 96-well plates. To select for GPI-deficient T-cells, the cells were cultured for 10 days in a medium containing rat T-STIII and 2 nM proaerolysin (ProAER). The frequency of ProAER-resistant (ProAER(r)) spleen T-cells from control rats ranged from 1.3 X 10(-6) to 4.8 X 10-6, While administration of three doses of 40 mg/kg N-ethyl-N-nitrosourea increased the frequency of ProAER(r) T-cells 100-fold at 4 weeks after dosing. FCM analysis of the cells in PrOAER(r) clones revealed that they were CD48-negative, and thus presumably GPI-deficient. Sequencing of Pig-A cDNA from six ProAERr clones indicated that they all contained alterations in the Pig-A protein coding sequence; five had base pair substitutions and one had multiple exons deleted. These results indicate that GPI-deficient spleen T-cells are Pig-A gene mutants and support the use of FCM analysis of GPI-deficient cells as a rapid assay for measuring in vivo gene mutation. Environ. Mal. Mutagen. 19:622-630, 2008. Published 2008 Wiley-Liss, Inc.