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L N Ruben

Publications and source records attributed to L N Ruben.

At least 55 records · Page 3Linked to original sources
PubMed1984

In vitro thymus suppression of hemagglutinin production in Xenopus laevis: location, drug and temperature sensitivity.

Suppression of splenic hemagglutinin (HA) production by allothymuses in vitro was further studied in Xenopus laevis, the South African clawed toad. Since thymic capacity to suppress splenic HA secretion into the culture medium is retained in animals previously exposed to N-methyl-N-nitrosourea (NMU), which destroys the thymus cortex in this species, suppressor function must be located in the thymus medulla. Reciprocal thymus-spleen combinations showed that normal thymus can suppress immunised spleen fragments from NMU-treated animals. Since Xenopus exposed to NMU are also devoid of helper function, thymus suppression acts directly on the antibody forming system. Cyclophosphamide removed thymic suppression and enhanced spleen fragment antibody production, while Cyclosporin A enhanced thymic suppression and blocked HA production. Therefore, antigenic stimulation of thymic suppression and antibody production are inversely related in this species. Long-term storage of Xenopus in the cold increased lymphoid cellularity of the thymus medulla, but thymuses from cold-stored animals could not suppress normal spleen fragments and their spleens were not suppressed by normal thymuses. Thus, ectotherms may retain immunological capacity when subjected to prolonged cold by a loss of thymic suppression.

Animals↗
PubMed1984

TNP-Ficoll response in Xenopus laevis: substitution and reconstitution in thymectomized animals.

The capacity to respond to haptenated Ficoll, though thymus-independent in mammals, is lost in Xenopus laevis following thymectomy at any stage of development. This capacity can be restored to thymectomized Xenopus by whole allogeneic thymus implants, by thymus implants from animals treated with N-methyl-N-nitrosourea (which have an active thymus medulla but no cortex, and which lack certain thymus-dependent immunological functions), and Concanavalin A. These results are discussed in terms of the cell populations and/or factors which may be involved.

Animals↗
PubMed1983

Hapten, carrier recognition and response by immunocytes of the primitive vertebrate, Notophthalmus viridescens.

These experiments were designed to test whether newt (Notophthalmus viridescens) immunocytes are able to recognize the hapten, 2,4,6-trinitrophenyl (TNP), separately from a heterologous erythrocyte (RBC) carrier. While a single priming injection with an erythrocyte species which is unrelated to the carrier of the TNP fails to stimulate amplification of the anti-TNP response, sequential (2X) priming provides about 50% as much amplification as a single priming injection of RBC homologous with the carrier. The anti-carrier response is not increased by sequential priming with the unrelated RBC. Moreover, sequential priming with RBC homologous with the carrier species initiates a suppression of the anti-hapten response without affecting anti-carrier activity levels. Thus the recognition and regulation of responses to a hapten and its carrier may be unlinked in this species.

Animals↗
PubMed1983

Some characteristics of thymus suppression of antibody production in vitro in Xenopus laevis, the South African clawed toad.

Organ cultures were used to test whether thymus suppression of antibody production by spleen cells of Xenopus laevis is antigen inducible, antigen specific, or genetically restricted when a thymus-dependent (TD) antigen, horse erythrocytes (HRBC), is injected in vivo. The capacity of mammalian thymus-independent (TI) antigens, e.g. TNP-Ficoll (TI-2) and TNP-LPS (TI-1) to induce thymus suppression of the anti-HRBC) response was also tested. Additionally, the susceptibility of TI spleen responses to thymus suppression was studied. Auto- and allogeneic thymus and spleen combinations were compared to spleen cultured alone with respect to hemagglutinin titers secreted into the culture medium. The results suggest that thymus suppression of a TD response in this species is antigen inducible. Moreover, depending on the antigen used either antigen specific or unspecific suppression will be generated. Both can function across allogeneic boundaries. Responses to TI antigens are not subject to thymus suppression.

Animals↗
PubMed1982

Evidence for low-molecular weight antibodies in the serum of a urodele amphibian, Ambystoma mexicanum.

Adult axolotls (A. mexicanum) were hyperimmunized with the haptenic determinant, azobenzene-arsonate (ARS). Specific antibodies were isolated from their serum by immune-affinity chromatography on immobilized ARS columns. Analysis of the specific ARS-binding molecules by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) indicated that these animals were capable of producing both high molecular-weight (presumably IgM) and low molecular-weight antibodies to the ARS hapten. The low molecular-weight anti-ARS antibody produced by one inbred colony of axolotls did not show any restricted heterogeneity, as assessed by isoelectric focusing. Our results suggest that regulatory events, not the absence of genetic information, may be responsible for the apparent lack of Ig isotype diversity in this species.

Ambystoma↗
PubMed1982

Limitations in response capacity of the newt, Notophthalmus viridescens, to soluble and particulate antigens.

We have investigated the cellular basis of the failure of primitive extant vertebrates, e.g. Notophthalmus viridescens, the American common newt, to respond to soluble thymus-dependent (TD) antigens, e.g. keyhole limpet hemocyanin (KLH). We have found that KLH can be used to prime for amplification of a response to hapten, 2,4,6-trinitrophenyl (TNP) when it is conjugated to KLH, only if both the unconjugated and conjugated KLH are adsorbed onto bentonite particles. The response is monitored in terms of antigen binding cells in the spleen. Moreover, prior injection of colloidal carbon, which is actively engulfed by phagocytes throughout the body, will prevent the response from taking place. Injection of colloidal carbon diminished responses to heterologous erythrocytes and to soluble or bentonite-coated 2,4-dinitrophenylated (DNP) dextran. Comparable colloidal carbon treatment did not reduce response levels to either soluble or bentonite adsorbed TNP-lipopolysaccharide (LPS) of E. coli. We suggest that the limitation in response capacity to soluble TD antigens may be associated with regulatory phagocytes. Moreover, the phagocytic cells of this primitive vertebrate appear to mediate responses to naturally particulate TD antigens and certain thymus-independent (TI) carriers, e.g. dextran, but not to LPS.

Animals↗
PubMed1981

Internal histoincompatability during amphibian metamorphosis?

Larval amphibia are immunologically competent. Yet during metamorphosis, various regressive and progressive processes replace larval with adult structures. These new structures are thought to arise in an immunological environment which provides protection from rejection of non-larval targets. Pre-metamorphic larvae and post-metamorphic adults require carrier-primed amplification in order to generate an anti-hapten response. However, we find that the response to a single challenge of the hapten, TNP, conjugated to a thymus-dependent (TD) carrier, sheep erythrocytes, is substantial in the absence of carrier priming early in metamorphosis. In contrast, the response to TNP on LPS, a thymus-independent carrier, is unaffected by metamorphosis, We suggest that a unique internal histoincompatibility between larval and adult lymphoid cells may provide a substitute for the carrier-priming requirement in the hapten-TD carrier response during metamorphosis.

Animals↗
PubMed1979

The effect of adult thymectomy upon helper function in Xenopus laevis, the South African clawed toad.

Carrier-primed helper activity enhancing anti-hapten (TNP-) responses in young adult Xenopus laevis reached peak levels 2-4 days after a low dose challenge (0.005% RBC) of unconjugated carrier. It fell quickly to negligible levels by 10 days. Adult thymectomized (ATx) animals were consistently unable to generate substantial levels of hapten-specific antigen-binding spleen cell (ABC) activity. Since ATx does not severely reduce splenic ABC responses to the high dose (10% RBC) of carrier used for hapten challenge, the results suggested a role for Xenopus adult thymus in carrier-specific enhancement of an anti-hapten response.

Animals↗
PubMed1978

The effects of alpha and beta adrenergic agents on spleen cell antigen binding in four amphibian species.

Adults of two urodele amphibian species (Triturus cristatus carnifex and Cynops hongkongensis) and two anuran species (Rana temporaria and Xenopus laevis laevis) were immunized with a 25% suspension of sheep or horse erythrocytes. After eight or 14 days, splenic lymphocytes were removed, and their specific red cell-binding capacities tested by immunocytoadherence. Antigen-binding cells were classified as high-dose nonsecretory (S-) or secretory (S+), according to whether they bound a single layer or several layers or erythrocytes. The stimulation of both alpha and beta adrenoreceptors reduced the numbers of S+ rosettes formed by Triturus and Cynops lymphocytes, whereas a beta agonist increased and an alpha agonist decreased S+ rosette formation by Rana and Xenopus splenic lymphocytes. These effects were blocked by alpha and beta adrenoreceptor antagonists. Low-dose immunization of Xenopus with a 0.0025% suspension of sheep erythrocytes gave a minimal number of S+ rosettes two and eight days after immunization, and beta adrenoreceptor stimulation had no effect on antigen binding. These results are discussed in terms of the distribution of alpha and beta adrenoreceptors in amphibians and possible relationships between S+ and high-dose S- antigen-binding cells, and support the view that functional lymphocyte heterogeneity exists in these lower vertebrates.

Amphibians↗