Posttranscriptionally mediated decreases in folylpolyglutamate synthetase gene expression in some folate analogue-resistant variants of the L1210 cell. Evidence for an altered cognate mRNA in the variants affecting the rate of de novo synthesis of the enzyme.

L1210 cell variants resistant to edatrexate (EDX) were isolated by selection in vivo during therapy with this folate analogue. Among the variants selected, seven (L1210/EDX-4 to -7 and L1210/EDX-12 to -14) were found to exhibit 2-23-fold lower levels of folylpolyglutamate synthetase (FPGS) activity compared with parental L1210 cells. Lower levels of FPGS activity in cell-free extract from these variants using EDX as substrate were characterized by the same relative decrease in value for Vmax with no change in apparent Km.

Different antifolate-resistant L1210 cell variants with either increased or decreased folylpolyglutamate synthetase gene expression at the level of mRNA transcription.

L1210 cell variants selected in the presence of the lipophilic dihydrofolate reductase inhibitor, metoprine, expressed increased levels of one-carbon, reduced folate transport inward (Sirotnak, F. M., Moccio, D.

Rapid decline in folylpolyglutamate synthetase activity and gene expression during maturation of HL-60 cells. Nature of the effect, impact on folate compound polyglutamate pools, and evidence for programmed down-regulation during maturation.

These studies in HL-60 cells examined the regulation of folylpolyglutamate synthetase (FPGS) activity at the level of gene expression during terminal maturation. Following addition of 210 mM Me2SO to cultures of HL-60 cells at a concentration that induces maturation of 85-90% of the cells, FPGS activity, but not folylpolyglutamate hydrolase (FPGH) activity, was reduced 2-7-fold within 1-5 days. The initial decline in FPGS activity preceded any effect of Me2SO on rate of growth and the increase in appearance of nitro blue tetrazolium-positive cells, a marker of cellular maturation, and the decrease after 5 days of exposure to Me2SO was solely accounted for by a 7-fold decrease in value for Vmax.

Coombs-positive autoimmune hemolytic anemia and postinfantile giant cell hepatitis in children.

We report a 23-month-old girl and a 9-month-old boy who presented with autoimmune hemolytic anemia followed by recurrent episodes of severe hepatitis. The first episode of hepatitis occurred 1 week and 15 months after presentation, respectively. Histologically, the livers showed loss of lobular architecture with diffuse giant cell transformation of hepatocytes and portal and pericellular fibrosis.

Analysis of three distinct Ly6-A-related cDNA sequences isolated from rat kidney.

Mouse Ly6A and Ly6C cDNA probes were hybridized to total RNA of rat tissues and, as in mouse, the highest level of Ly6-related transcripts was detected in kidney. Therefore, Ly6-related cDNA clones were isolated from a commercial rat kidney cDNA library in lambda gt11. Four of these (RK3, RK6, RK10, and RK11) have been fully characterized, and represent transcripts from three distinct genes.

The CD59 antigen is a structural homologue of murine Ly-6 antigens but lacks interferon inducibility.

A cDNA encoding the human leukocyte antigen CD59 has been isolated from the erythroid cell line K-562 and its identity confirmed through expression in COS cells. Northern blotting reveals three message species of approximately 800, 1400 and 2000 bases in size, which are constitutively expressed in all lymphoid, erythroid, myeloid, and neural cell types tested thus far. Southern blotting of human DNA indicates a pattern consistent with the presence of a single gene, which has been mapped to chromosome 11 by somatic cell hybrids.

I.29 lymphoma cells express a nonmutated VH gene before and after H chain switch.

The I.29 B cell lymphoma consists of IgM+ and IgA+ cells which express the same germ-line VH gene. IgA+ cells of the I.

N-terminal and cDNA characterization of murine lymphocyte antigen Ly-6C.2.

The Ly-6C.2 molecule was purified from K36 tumor cells by affinity chromatography and gel filtration. The electrophoretically homogeneous preparation, with m.

Demonstration of phosphatidylinositol anchors on Ly-6 molecules by specific phospholipase C digestion and gel electrophoresis in octylglucoside.

Release by phosphatidylinositol-specific phospholipase C is frequently provided as evidence for membrane anchorage of a protein through phosphatidylinositol. Demonstration that the enzyme removes a lipophilic moiety from the protein is stronger evidence, and is presented here for members of the Ly-6 family of lymphocyte antigens: Ly-6A, C and E. Treatment of these molecules with the enzyme greatly increased their electrophoretic mobilities on polyacrylamide gels containing nonionic detergent.

Identical twins concordant for Crohn's disease.

Identical twin adolescent girls developed Crohn's disease within 15 months of each other. Clinical symptoms, growth retardation, barium studies, disease course, and pathologic findings at the time of resection were remarkably similar. Seventeen pairs of twins concordant for Crohn's disease have now been reported, but only four discordant pairs.

Specificity of immunoglobulin heavy chain switch correlates with activity of germline heavy chain genes prior to switching.

IgM+ cells cultured from the I.29 B cell lymphoma can be induced with lipopolysaccharide (LPS) or, to a greater extent, with LPS plus anti-idiotype antibody to switch to IgG2a, IgE or IgA expression. The isotype switch is accompanied by rearrangement of immunoglobulin (Ig) heavy (H) chain genes.

Atypical presentation of childhood acquired immune deficiency syndrome mimicking Crohn's disease: nutritional considerations and management.

A child with acquired immune deficiency syndrome became severely malnourished presumably as a result of multiple gastrointestinal infections, with numerous organisms including campylobacter, giardia, and cryptosporidium. These opportunistic infections preceded laboratory evidence of immune deficiency. Despite severe diarrhea and marked weight loss, there was no laboratory evidence of significant malabsorption.

Induction of immunoglobulin isotype switching in cultured I.29 B lymphoma cells. Characterization of the accompanying rearrangements of heavy chain genes.

The murine B cell lymphoma I.29 contains cells expressing surface IgM or IgA with identical heavy chain variable regions (9, 25, and D. Klein and J.

Rearrangements and deletions of immunoglobulin heavy chain genes in the double-producing B cell lymphoma I.29.

The B cell lymphoma I.29 consists of a mixture of cells expressing membrane-bound immunoglobulin M (IgM) (lambda) and IgA (lambda) of identical idiotypes. Whereas most of the cells express either IgM or IgA alone, 1 to 5% of the cells in this tumor express IgM and IgA simultaneously within the cytoplasm and on the cell membrane (R.

Human skin fibroblasts from individuals genetically predisposed to cancer are sensitive to an SV40-induced T antigen display and transformation.

In the present study we have used a viral probe to determine the genetic susceptibility of fibroblastic cell strains derived from individuals with hereditary adenomatosis of the colon and rectum (ACR), an autosomal dominant trait. This report shows an increased sensitivity of apparently karyologically-normal diploid skin fibroblasts from ACR individuals to an SV40-induced T antigen display and transformation. None of the SV40-transformed cells grew as tumors in athymic mice and they all appeared to have a finite life span.

Effects of exogenous androgen treatment on X-chromatin.

In studying a possible hormonal influence on X-chromatin frequency, buccal smears from two groups of women, one on androgen therapy and one not on androgen therapy, were compared. Both groups were nonmenstruating, renal dialysis patients, 41 to 69 years of age. For each patient the X-chromatin frequency was determined from 100 analyzable and intact buccal mucosa cells.