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Biomedical subjects

H Friedman

Publications and source records attributed to H Friedman.

At least 361 records · Page 20Linked to original sources
PubMed1983

Agar microdroplet assay for delayed hypersensitivity to Legionella pneumophila serogroup 1.

An agarose microdroplet technique was utilized to assess the cellular immunity of guinea pig lymphoid cells to Legionella pneumophila antigen in vitro. Both direct and indirect migration inhibition procedures were shown to be capable of detecting sensitization of guinea pigs to L. pneumophila antigens. Animals injected with adjuvant alone or unrelated antigens did not yield spleen cells responsive to L. pneumophila, indicating the specificity of the response. Migration inhibition factor induction by Legionella antigen in vitro correlated well with skin test responses in vivo. The positive reaction detected by migration inhibition occurred at times similar to that of skin reactivity but later than that of the earliest serum antibody titers. The assay appears to be useful for monitoring sensitization to Legionella and may be applicable to the study of cell-mediated immunity to this bacterium in infected individuals.

Animals↗
PubMed1983

Blastogenic responsiveness of spleen cells from guinea pigs sensitized to Legionella pneumophila antigens.

An in vitro leukocyte blastogenic assay was utilized to establish an in vitro correlate of cell-mediated immunity to Legionella pneumophila antigen with spleen cells from sensitized guinea pigs. Incubation of spleen cells from sensitized but not normal guinea pigs with graded amounts of killed whole cell Legionella bacteria or sonicate derived from the bacteria resulted in an antigen-induced blast cell proliferation as evidenced by an increased uptake of [3H]-thymidine into spleen cell cultures. Peak responses occurred approximately 4-6 days after incubation of the spleen cells with antigen. Sensitivity of spleen cells from animals immunized with Legionella vaccine in adjuvant persisted for at least 150 days, while responses after infection of guinea pigs with viable bacteria persisted about 4-6 weeks. The blastogenic responses of the spleen cells to Legionella antigen appeared to be a correlate of cell-mediated immunity.

Animals↗
PubMed1983

Legionella pneumophila-induced immunostimulation and blastogenesis of normal mouse spleen cells in vitro.

Cell-free sonic extracts prepared from Legionella pneumophila serogroup 1 were found to enhance the uptake of [3H]thymidine by normal mouse spleen cell cultures in vitro and also stimulate an enhanced antibody response to sheep erythrocytes, both in immunized and nonimmunized cultures. Increased background antibody responses to other erythrocyte species also occurred, indicating that the Legionella antigen was a polyclonal B cell activator. A purified cell wall component with physicochemical properties relatively similar to endotoxin, but without toxicity for mice, was found to have mitogenic activity for normal mouse spleen cells and immunostimulatory properties for anti-erythrocyte antibody response. Heating the sonicate or the purified somatic antigen for 10 min diminished immunoenhancing activity but had little effect on mitogenic properties. These results point to the complex effects of Legionella-derived antigens on normal lymphoid cell function and indicate that antigens derived from Legionella have marked immunomodulatory properties.

Animals↗
PubMed1983

Dimethyl sulfoxide-induced transglutaminase activity in murine-derived Friend erythroleukemia cells.

Friend erythroleukemia cells (FL cells) derived from DBA/2 mice may be induced to differentiate in vitro by addition of dimethyl sulfoxide (DMSO) to the culture medium. Transglutaminase (glutaminyl-peptide gamma-glutamyltransferase, EC 2.3.2.13) (TGase) activity was detected in the lysates of uninduced FL cells and was markedly increased in DMSO-treated cells. DMSO induced TGase activity of differentiating FL cells in a dose-dependent manner over the concentration range 0-280 mM. The increase in TGase activity was observed after 1 day's cultivation of the cells with 280 mM DMSO and continued to 4 days. Another differentiation inducing agent, butyric acid (1.4 mM), was as effective as DMSO in enhancing TGase activity in FL cells. Treatment of controls, a lymphoma cell line and mouse erythrocytes, with DMSO or butyric acid had no effect. These results suggest that the increase in TGase activity in DMSO- or butyric acid-treated FL cells may be related to cell differentiation.

Acyltransferases↗
PubMed1983

Variation in antigenic determinants of p53 transformation-related protein obtained from various species.

p53 is a cellular-encoded transformation-related protein. It is synthesized at elevated levels in tumor cells but has also been detected at low concentrations in several types of nontransformed cells. The p53 of tumor cells is immunogenic and elicits specific antibody production. The antigenic determinants of the p53 protein were studied by specific binding to anti-p53 monoclonal antibodies obtained from the RA3-2C2, PAb122, and PAb421 established hybridoma cell lines, and their conservation was followed in various animal species. We found that whereas mouse p53 efficiently immunoprecipitated with all three anti-p53 monoclonal antibodies, human and rat p53 bound PAb122 and PAb421 but lacked a determinant binding RA3-2C2. The hamster p53 molecule represented a third category, which immunoprecipitated with polyclonal anti-p53 antibodies but failed to bind all three monoclonal antibodies analyzed here. Using these monoclonal antibodies, we detected no variations between p53 found in transformed and p53 found in nontransformed cells, within a given species. The results also showed that RA3-2C2, which recognizes a mouse-specific determinant, binds a site located at a proteolytic digestion fragment of the p53 molecule that differs from that containing PAb122 and PAb421 recognition site(s). p53 is a single protein that can be immunoprecipitated through different antigenic determinants that vary between species.

Animals↗
PubMed1983

Mechanism of glucocorticoid action on murine natural killer cell activity.

With the use of an in vitro model system, the mode of action of glucocorticoids on murine natural killer (NK) cell-mediated cytotoxicity of tumor cells was investigated. Of the steroids tested, only the glucocorticoids notably suppressed NK activity. Glucocorticoids were not toxic to the NK effector cell since inhibitors of protein synthesis protected NK activity from the suppressive action of glucocorticoids. Glucocorticoid-treated C57BL/6J spleen cells, although suppressed in NK activity, were unable to suppress the NK activity of normal syngeneic spleen cell cultures. Similarly, the supernatants of glucocorticoid-treated cultures were also unable to suppress normal NK activity. Thus a role for suppressor cell activity or soluble suppressive factors was excluded. Results of analyses of the NK activity of Percoll-fractionated glucocorticoid-treated C3H/HeN (nu/nu) spleen cells at the single-cell level demonstrated that NK effector cells could efficiently bind to YAC-1 lymphoma cells but were incapable of inducing cytolysis. Moreover, the production of NK cytotoxicity factor(s) in tumor cell-stimulated nude mouse spleen cell cultures was severely depressed after glucocorticoid treatment. The results of these studies suggest that glucocorticoids suppress murine NK activity by acting directly on the NK effector cells, possibly by inhibiting the formation or release of specific effector molecules that are cytotoxic to NK-sensitive tumor cells.

Animals↗
PubMed1982

Comparison of lyophilized and frozen microtiter systems for routine MIC testing in the clinical laboratory.

Frozen microtiter plates (Micro-Media Systems, Inc.) and lyophilized microtiter plates (Sensititre--Seward Laboratory/Gibco Diagnostics) were used to perform simultaneous MIC determinations. Specimens were obtained from blood, urine and other clinical isolates. The authors found that there was good correspondence of results with the frozen microtiter MIC plates and the lyophilized microtiter MIC plates. After careful evaluation, the authors conclude that the lyophilized product is as stable and as reproducible as the frozen product. The lyophilized product is more easily and conveniently stored, has a longer shelf life and is more flexible.

Anti-Bacterial Agents↗
PubMed1982

Cryptococcal capsular polysaccharide-induced modulation of murine immune responses.

Cryptococcus neoformans, an opportunistic fungal pathogen, often causes serious and life-threatening infections in immunocompromised hosts as well as in normal individuals. In the present study, purified cryptococcal capsular polysaccharide antigen was examined for its effect on several parameters of immune response and its ability to induce immune response to itself. Injection of the antigen into mice resulted in a dose-related specific antibody response which was detected at the individual antibody plaque-forming-cell level by a hemolytic assay in gel. Relatively low doses of cryptococci induced a maximal response, whereas higher doses resulted in a markedly depressed response. The antibody response to the cryptococcal capsular polysaccharide antigen appeared to be T cell independent and regulated by suppressor T cells, since mice injected with antilymphocyte serum or antithymocyte serum showed specific antibody responses to the antigen that were higher than those of untreated mice. It also markedly affected the in vitro mixed-lymphocyte reaction when added to cultures of mouse spleen cells being challenged in vitro with mitomycin C-treated allogeneic cells. The lower doses stimulated the response, whereas higher doses suppressed it. The macrophage response to yeast cells but not opsonized sheep erythrocytes was also modulated by the cryptococcal antigen.

Animals↗