Establishment of a novel anaplastic large-cell lymphoma-cell line (COST) from a 'small-cell variant' of ALCL.

Anaplastic large-cell lymphoma (ALCL) is a distinct biological and cytogenetic entity with a broad spectrum of morphological features (common type, small-cell variant and lymphohistiocytic variant). Few cell lines of ALCL are available and they all originate from primary tumors demonstrating the common type morphology (ie large-sized lymphoma cells). We established a new ALCL cell line (COST) from the peripheral blood of a patient with a small-cell variant of ALCL, at diagnosis. Cells growing in vitro and in SCID mice consisted of two populations, that is, small- and large-sized cells as seen in the patient's tumor. Both large and small malignant cells were positive for CD43/MT1 T-cell associated antigen, perforin, granzyme B and TIA-1, but negative for CD2, CD3, CD5, CD7, CD4 and CD8 antigens. Standard cytogenetic studies as well as multiplex FISH confirmed the presence of the canonical t(2;5)(p23;q35) translocation, but also revealed additional numerical and structural abnormalities. The COST cell line is the first ALCL small-cell variant cell line, and thus provides a potentially useful tool for further functional and molecular studies that should improve our understanding of the small-cell variant of ALCL, which is more frequently complicated by a leukemic phase.

Production of phosphatidylinositol 3,4,5-trisphosphate and phosphatidic acid in platelet rafts: evidence for a critical role of cholesterol-enriched domains in human platelet activation.

Glycosphingolipid- and cholesterol-enriched membrane microdomains, called rafts, can be isolated from several mammalian cells, including platelets. These microdomains appear to play a critical role in signal transduction in several hematopoietic cells, but their function in blood platelets remains unknown. Herein, we first characterized the lipid composition, including the fatty acid composition of phospholipids, of human platelet rafts. Then their role in platelet activation process was investigated. Interestingly, thrombin stimulation led to morphological changes of rafts correlating with the production of lipid second messengers in these microdomains. Indeed, we could demonstrate for the first time that a large part of the stimulation-dependent production of phosphatidic acid and phosphoinositide 3-kinase products was concentrated in rafts. Moreover, cholesterol depletion with methyl-beta-cyclodextrin disrupted platelet rafts, dramatically decreased the agonist-dependent production of these lipid signaling molecules, and impaired platelet secretion and aggregation. Cholesterol repletion restored the physiological platelet responses. Altogether our data indicate that rafts are highly dynamic platelet membrane structures involved in critical signaling mechanisms linked to the production of lipid second messengers. The demonstration of phosphatidylinositol 3,4,5-trisphosphate production in rafts may have general implications for the understanding of the role of this key second messenger found ubiquitously in higher eucaryotic cells.

Relationship between the fatty acid composition of rat lymphocytes and immune functions.

The effects of dietary lipids on the fatty acid composition, activation and proliferation of lymphocytes were investigated. Weanling male Wistar rats were fed for 8 weeks on one of two low-fat diets which contained 50 g lipid/kg, or one of two high-fat diets containing 200 g lipid/kg, from either coconut oil or soyabean oil. The fatty acid composition of phospholipids from splenocyte membranes was affected by dietary lipid manipulation, and these differences influenced lymphocyte functions. Increased levels of linoleic acid in spleen lymphocytes correlated negatively with interleukin-2 receptor alpha-chain expression determined either by measuring the mean fluorescence or by the proportion of cells staining positive for CD25, and with the cell proliferation index. However, we found a positive correlation between interleukin-2 receptor alpha-chain expression determined by measuring the mean fluorescence and the cell proliferation index with the oleic acid concentration of spleen lymphocytes. Since phospholipid hydrolysis occurs early in lymphocyte activation, immunosuppressive effects induced by polyunsaturated fatty acids, described in the literature, could be due to an increase of linoleic acid or a decrease of oleic acid affecting many components of plasma-membrane-associated events involved in lymphocyte activation.

In vivo effects of olive oil-based lipid emulsion on lymphocyte activation in rats.

Numerous studies suggest that immune function may be compromised by lipid emulsions rich in polyunsaturated fatty acids, especially linoleic acid. In our study, we compared the effect of a new olive oil-based lipid emulsion (ClinOleic(R)) containing 18% linoleic acid, and an emulsion based on soybean oil (Ivelip(R); 52% linoleic acid) on lymphocyte functions. Weaning Wistar rats (n= 24) were fed for 4 weeks on an oral diet that contained 12% of total energy as lipids from soybean oil. Then they received, during 6 days, a total parenteral nutrition (260 kcal/kg/d) in which 12% of total energy was brought by one of the two lipid emulsions. The fatty acid profile of spleen lymphocyte phospholipids reflected lipid intakes, with a higher content of oleic acid in ClinOleic(R) group and linoleic acid in Ivelip(R) group. A greater proportion of cells expressed the interleukin-2 receptor a-chain (CD25) after administration of ClinOleic(R) when compared to Ivelip(R) (55.43 +/- 3.47 vs 45.48 +/- 3.26%, P<< 0.05). Moreover, the CD25 expression was positively correlated with oleic acid content of spleen lymphocyte phospholipids (r= 0.500, P<< 0.018). These results show that ClinOleic(R) is able to induce, in vivo, a greater proportion of cells expressing CD25, and suggest that oleic acid could have a role in the observed effects.