Biomedical subjects

A Helmberg

Publications and source records attributed to A Helmberg.

22 records · Page 2Linked to original sources

PubMed1990

Glucocorticoid-regulated gene expression in the immune system. Analysis of glucocorticoid-regulated transcripts from the mouse macrophage-like cell line P388D1.

To further elucidate the molecular mechanisms underlying glucocorticoid-mediated immune suppression, we have exploited cDNA cloning and subtractive screening methods to identify glucocorticoid-regulated transcripts in the mouse macrophage-like cell line, P388D1. Two of the three isolated glucocorticoid-regulated mRNA species corresponded to genes potentially important to immunoregulation: one glucocorticoid-suppressed mRNA species probably encoded the previously uncloned 3-hydroxy-3-methylglutaryl coenzyme A reductase, an enzyme that appears important for in vitro immune responses. The other mRNA species showed glucocorticoid-increased mRNA steady-state levels and was transcribed from an endogenous ecotropic type C retroviral locus. This transcript gives rise to a protein (transmembrane retroviral protein, formerly p15E), which, along with its feline and human homologs, has been implicated in immunosuppression caused by mouse, cat, and human retroviruses. Our results raise the possibility that the immunosuppressive activity of glucocorticoids might be mediated, in part, by regulating the expression of the above immunoregulatory proteins.

Animals↗

PubMed1989

Mouse Vk gene classification by nucleic acid sequence similarity.

Analyses of immunoglobulin (Ig) variable (V) region gene usage in the immune response, estimates of V gene germline complexity, and other nucleic acid hybridization-based studies depend on the extent to which such genes are related (i.e., sequence similarity) and their organization in gene families. While mouse Igh heavy chain V region (VH) gene families are relatively well-established, a corresponding systematic classification of Igk light chain V region (Vk) genes has not been reported. The present analysis, in the course of which we reviewed the known extent of the Vk germline gene repertoire and Vk gene usage in a variety of responses to foreign and self antigens, provides a classification of mouse Vk genes in gene families composed of members with greater than 80% overall nucleic acid sequence similarity. This classification differed in several aspects from that of VH genes: only some Vk gene families were as clearly separated (by greater than 25% sequence dissimilarity) as typical VH gene families; most Vk gene families were closely related and, in several instances, members from different families were very similar (greater than 80%) over large sequence portions; frequently, classification by nucleic acid sequence similarity diverged from existing classifications based on amino-terminal protein sequence similarity. Our data have implications for Vk gene analyses by nucleic acid hybridization and describe potentially important differences in sequence organization between VH and Vk genes.

Animals↗

PubMed1989

An orally administered bacterial immunomodulator primes rabbit neutrophils for increased oxidative burst in response to opsonized zymosan.

To assess the potential effect of an orally administered immunomodulator, consisting of a lysate of seven different bacteria, on polymorphonuclear leukocyte (PMN) function, rabbits were fed this preparation for five consecutive days via a gastric tube. On day 6, PMN were separated from peripheral blood and oxidative burst was triggered by opsonized zymosan or 12-O-tetradecanoylphorbol-13-acetate and quantitated on a single-cell basis. This study presents the extension of an existing flow cytometric method, leading to the possibility of quantitating single-cell oxidative burst triggered by particulate (instead of only soluble) stimuli. By this means, treated animals showed statistically significant increased oxidative burst reactions compared with the control group. The data provide evidence that oral application of a bacterial immunomodulator leads to a primed state in PMN for increased oxidative activity in response to a particulate stimulus. This offers the possibility that the beneficial effect of similar treatment in humans may in part be due to comparable mechanisms.

Adjuvants, Immunologic↗

PubMed1985

Enzyme-linked immunoassay to monitor the purification of, and to screen for monoclonal antibodies against, C3b receptor.

An enzyme-linked immunosorbent assay both to screen for monoclonal anti-bodies to the C3b receptor and to monitor its purification was developed. The test requires only purified C3, converted to either the hemolytically no longer active iC3 or C3b. An NP-40 lysate of tonsil cells can be used as a source of CR1 in this test which works best under hypotonic conditions facilitating the interaction of iC3/C3b and CR1. Two monoclonal antibodies to CR1 were produced using this test for the screening of hybridomas. The identity of the molecule recognized by these antibodies with CR1 is demonstrated by immunoprecipitation and Western blot studies, as well as immunofluorescence and immunoperoxidase staining of cells and tissues known to contain CR1. Fractions from lentil-lectin and DEAE-Sephadex columns containing CR1 can be identified using this test.

Antibodies, Monoclonal↗