Cytotoxic T lymphocytes from humans with adenocarcinomas stimulated by native MUC1 mucin and a mucin peptide mutated at a glycosylation site

MUC1 mucin peptides stimulated cytotoxic T lymphocytes (CTL) from humans with adenocarcinomas. Peripheral blood mononuclear cells, tumor-draining lymph node cells, or tumor-infiltrating lymphocytes were stimulated using mono-nuclear cells from humans with adenocarcinomas of breast or ovary, respectively, using (a) a native MUC1 mucin tandem repeat peptide of 20 amino acids (MUC1-mtr1) plus recombinant human interleukin-2 (IL-2), (b) the mutated (T3N) MUC1-mtr1 plus IL-2, or (c) immobilized anti-CD3 plus IL-2, or (d) IL-2 alone. The CTL stimulated by each of these four conditions were predominately CD4+. However, the CTL stimulated by either the native MUC1-mtr1 or (T3N) MUC1-mtr1 showed 5-10 times greater cytotoxicity of a breast cancer cell line that expresses MUC1 compared to CTL stimulated by either anti-CD3 + IL-2 or IL-2 alone. Each incubation condition generated CTL with different variable beta gene families of T-cell receptors, implying an oligoclonal expansion of a limited CTL repertoire for each. Thus, peptide-stimulated T cells showed expression of cytotoxic cells, which was not induced by nonspecific (anti-CD3 or IL-2) stimulation.

Human CD4+ and CD8+ T lymphocytes are both cytotoxic to Toxoplasma gondii-infected cells

Studies to determine if Toxoplasma gondii-specific human T cells lyse parasite-infected cells have yielded conflicting results. Furthermore, attempts to obtain human cytotoxic CD8+ T lymphocytes have been difficult because of the lack of a reproducible system for their generation. By using paraformaldehyde-fixed, T. gondii-infected peripheral blood mononuclear cells as antigen-presenting cells, we developed a method whereby T. gondii-specific T-cell lines can be reproducibly generated. Six T. gondii-specific T-cell lines were generated from an individual chronically infected with T. gondii. Cytofluorometric analysis of these lines revealed > 99% CD3+, 85 to 95% CD3+ alpha beta T-cell-receptor-positive (TCR+), 5 to 9% CD3+ gamma delta TCR+, 50 to 70% CD4+, and 20 to 40% CD8+ cells when cells were examined during the first 3 weeks of stimulation and >99% CD3+, >99% CD3+ alpha beta TCR+, < 1% CD3+ gamma delta TCR+, 20 to 40% CD4+, and 60 to 80% CD8+ cells when cells were examined between 5 and 11 weeks. Both CD4+ and CD8+ T cells had remarkable cytotoxic activity against T. gondii-infected target cells (30 to 50% specific Cr release at an effector-to-target ratio of 30:1) but not against uninfected target cells ( < 10% at an effector-to-target ratio of 30:1). Cytotoxic activity by the whole T-cell lines was not T. gondii strain specific. Whole T-cell lines were cytotoxic for target cells infected with the C56 and ME49 strains and the RH strain (which was used to infect peripheral blood mononuclear cells). T. gondii-specific T-cell lines displayed the predominant expression of V beta 7 TCR. The CDR3 regions of the V beta 7 TCRs of these T-cell lines showed a striking degree of sequence identity (oligoclonality). T-cell lines obtained by the method reporter here can be used to characterize functional activity of T-lymphocyte subsets in humans infected with T. gondii.

Tissue-specific regulation by vitamin D status of nuclear and mitochondrial gene expression in kidney and intestine

Vitamin D is responsible, through the actions of its metabolite, 1 alpha,25-dihydroxyvitamin D3 [1 alpha,25-(OH)2D3], for the generation of a wide array of biological responses, particularly in the intestine, kidney, and bone. 1 alpha,25-(OH)2D3 is known to interact with its nuclear receptor to mediate the regulation of gene transcription. Although many genes and gene products have been shown to be regulated by 1 alpha,25-(OH)2D3 (e.g. calbindin-D28K in the intestine and kidney; collagen, osteocalcin,and osteopontin in bone), their recognition has been largely the result of empirical testing. In this report we have used subtractive hybridization analysis of complementary DNA libraries prepared from messenger RNA (mRNA) isolated from the intestine and kidney of vitamin D-replete or vitamin D-deficient chicks to identify genes for novel proteins whose steady state mRNA levels are regulated by dietary vitamin D status. In the kidney we observed the down-regulated expression of at least seven mitochondrially encoded transcripts and the up-regulated expression of five nuclear encoded genes, two of which are metallothionein and the beta-subunit of aldolase. In the intestine, six mitochondrially encoded transcripts are up-regulated, and seven nuclear encoded transcripts were either up- or down-regulated. Thus, in addition to identifying new nuclear encoded genes whose mRNAs are regulated by vitamin D status, our approach has demonstrated the tissue-specific regulation of mitochondrial gene expression in the intestine and kidney.

Regulation of folate and one-carbon metabolism in mammalian cells. IV. Role of folylpoly-gamma-glutamate synthetase in methotrexate metabolism and cytotoxicity

Chinese hamster ovary (CHO) cells expressing human and Escherichia coli folylpoly-gamma-glutamate synthetase (FPGS) activities were used as models to study factors regulating the cytotoxicity and metabolism of methotrexate (MTX). CHO cells expressing human FPGS metabolized MTX to polyglutamates characteristic of human cells. Cellular MTX accumulation and metabolism to polyglutamates were dependent on the level of FPGS activity and were unaffected by putative gamma-glutamyl hydrolase inhibitors. The sensitivity of cells continuously exposed to MTX was not influenced by FPGS activity. After short term exposure to MTX, cells expressing higher levels of FPGS were more sensitive to the drug. MTX was not transported into the mitochondria and MTX treatment had no effect on preexisting mitochondrial folates while cytosolic folates were converted to oxidized forms. Mitochondrial folate accumulation was significantly impaired by MTX treatment, suggesting that the mitochondrial folate transport system is specific for reduced folates.

Regulation of folate and one-carbon metabolism in mammalian cells. I. Folate metabolism in Chinese hamster ovary cells expressing Escherichia coli or human folylpoly-gamma-glutamate synthetase activity

Chinese hamster ovary (CHO) cell transfectants expressing various levels of human and Escherichia coli folylpoly-gamma-glutamate synthetase (FPGS) activity and possessing different folylpolyglutamate chain length distributions have been developed as models for folate and antifolate metabolism. The synthesis of pteroyltriglutamate was sufficient for normal cellular retention of folate and also overcame the phenotypic requirement for purines and thymidine of AUXB1, a CHO cell mutant lacking FPGS activity and lacking folylpolyglutamates. Only low levels of FPGS are required to enable cellular metabolism of folates to forms that are retained by mammalian cells. The higher levels found in mammalian cells are required for the synthesis of the long chain polyglutamate derivatives characteristic of mammalian cells. At low medium folate concentrations, folate accumulation by transfectants expressing human FPGS was not responsive to FPGS levels as the limiting step in metabolism was beyond the triglutamate, the chain length required for retention. The rate-limiting step in folate metabolism in cells expressing the E. coli enzyme was the conversion of diglutamate to triglutamate, and, at low FPGS levels, the E. coli enzyme was about 50-fold less effective than the human FPGS in enabling cellular folate accumulation. These data suggest that cellular accumulation of any folate analog whose mono- or diglutamate derivative is a poor substrate for FPGS would be very responsive to the level of FPGS activity.

Regulation of folate and one-carbon metabolism in mammalian cells. II. Effect of folylpoly-gamma-glutamate synthetase substrate specificity and level on folate metabolism and folylpoly-gamma-glutamate specificity of metabolic cycles of one-carbon metabolism

The effect of folylpoly-gamma-glutamate synthetase (FPGS) levels on folate accumulation was investigated in Chinese hamster ovary cells expressing various levels of human and Escherichia coli FPGS activity. At low medium folate concentrations, folate accumulation was limited by influx and was independent of FPGS activity except in cells expressing extremely low levels of FPGS. Essentially all transported folate was metabolized to retained polyglutamate derivatives, the chain length of which varied with the level of FPGS activity. As medium folate concentration increased through the physiological to the pharmacological range, cellular folate accumulation became proportional to FPGS activity and the chain length of intracellular folates decreased. At high folate concentrations, competition between substrates for FPGS limited the extent of polyglutamylation and less than 5% of transported folate was retained by the cell. Pteroyltriglutamates functioned as effectively as the longer chain length polyglutamates normally found in mammalian cells in the metabolic cycles of de novo purine and thymidylate biosynthesis but were unable to support glycine and methionine synthesis. Transfectants expressing human FPGS and containing folates of glutamate chain length ranging from four to eight were equally effective at supporting glycine synthesis, and transfectants expressing higher levels of FPGS were able to grow in the absence of methionine. Growth in the absence of methionine required high (nonphysiological) intracellular folate levels and longer chain length polyglutamates.

Vitamin D and psoriasis

Skin can serve as the source of vitamin D when exposed to sunlight so that cutaneous 7-dehydrocholesterol can be converted to the vitamin. Skin is also a target organ for the hormone form of vitamin D: 1,25-(OH)2D3. Both skin keratinocytes grown in tissue culture and samples of human skin have the nuclear receptor for 1,25(OH)2D3. New results suggest that this hormone or its analogs may be effective in treating some forms of psoriasis.

1,25(OH)2-vitamin D3, a steroid hormone that produces biologic effects via both genomic and nongenomic pathways

The hormonally active form of vitamin D is 1,25(OH)2-vitamin D3 [1,25(OH)2D3]. This seco-steroid is the key mediator of the vitamin D endocrine system which produces biological effects in over 28 target tissues. In these target tissues, the biological responses may be generated both by a signal transduction mechanism which involves a nuclear receptor for 1,25(OH)2D3 that modulates gene transcription or a signal transduction pathway which involves rapid opening of Ca2+ channels which are externally located on the plasma membrane. This paper reviews the evidence in support of the pleiotropic effects of this steroid hormone and presents evidence that the receptor of the genomic effects is likely to be separate from the receptor/membrane recognition element which initiates the rapid nongenomic biological effects.

Sequences near the CCAAT region and putative 1,25-dihydroxyvitamin D3-response element and further upstream novel regulatory sequences of calbindin-D28k promoter show DNase I footprinting protection

1,25-Dihydroxyvitamin D3, the hormonally active form of vitamin D (1,25(OH)2D3), plays a major role in the transcriptional regulation of the vitamin D-induced calcium binding protein calbindin-D28k in the chick intestine. Sequence-specific protein-DNA interactions within the promoter of the calbindin-D28k gene were studied by DNAse I footprinting analysis to obtain information on the mechanism by which the 1,25(OH)2D3 receptor and other transcription factors regulate its expression. Restriction fragments spanning nucleotides -679 to +44 of the calbindin-D28k gene were used as probes Intestinal nuclear extracts prepared from vitamin D-deficient chicks generated several protected regions. Two prominent areas of protection against DNase I digestion were located at nucleotides -595 to -572 (21 bp) and -372 to -337 (36 bp). The -372 to -337 protected segment includes a CACCC sequence motif. Additional protection regions (-333/-328, -319/-315 and -308/-304) were observed within and near the candidate chicken calbindin-D28k 1,25(OH)2D3-response element (-329/-313) and the CCAAT box (-326/-322). DNase I digestion patterns obtained with liver nuclear extracts, containing low levels of 1,25(OH)2D3 receptor, revealed weaker protein-DNA interactions in these regions.

Effect of essential fatty acid deficiency on the size and distribution of rat plasma HDL

Rat plasma high density lipoproteins (HDL) are comprised of two major particle size subpopulations, HDL1 (255 A-140 A) and HDL2 (140 A-84 A), in which the proportion of arachidonate in fatty acids of cholesteryl esters is greater than 50%. To determine whether decreased availability of arachidonate for cholesterol esterification would alter the distribution and/or amounts of the HDL subpopulations, we compared HDL subpopulations in EFA-deficient and control rats. To separate the effects of EFA deficiency and fat deficiency and to evaluate effects of different saturated fats, we used EFA-deficient diets that were fat-free or that contained 5% saturated fat. The control diets were the EFA-deficient diets plus 1% safflower oil. The saturated fats were hydrogenated coconut oil, hydrogenated cottonseed oil and saturated medium-chain triglycerides. All EFA-deficient diets decreased the proportion of the HDL1 subpopulation and the peak diameter of the HDL2 subpopulation. These changes appeared after quite brief EFA depletion in young rats and may be related to the increased liver cholesteryl ester concentrations typical of EFA-deficient rats.