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Biomedical subjects

H Friedman

Publications and source records attributed to H Friedman.

At least 433 records · Page 24Linked to original sources
PubMed1978

Stimulation of an enhanced in vitro immune response by a synthetic adjuvant, muramyl dipeptide.

Various subcellular bacterial fractions are known to enhance immune responses and serve as potent adjuvants. Muramyl dipeptide (MDP), a synthetic adjuvant mimicking a component of mycobacterial cell walls, enhances humoral immunity to soluble antigens and can increase macrophage cytotoxicity toward mastocytoma cells in vitro. In the present study MDP was found to enhance the hemolytic antibody plaque response of normal mouse spleen cells in vitro to SRBC at a level equal to or greater than that induced by Escherichia coli lipopolysaccharide. Furthermore, MDP was found to enhance the antibody response to SRBC nonspecifically in unimmunized spleen cell cultures, suggesting that similar to LPS the synthetic dipeptide may induce a generalized clonal expansion of committed lymphocytes and thus serve as a "polyclonal activator." MDP also enhanced the immune responsiveness of normal splenocytes to suboptimum concentrations of SRBC, indicating that this material may be useful in enhancing immunity in situations where there would normally be a poor immune response.

Adjuvants, Immunologic↗
PubMed1978

Differential immunosuppressive effects of ascites fluid from mastocytoma-bearing mice on primary vs secondary immunocyte responses.

The effects of immunosuppressive ascites fluids from mastocytoma-bearing mice on the primary vs secondary immune response to sheep red blood cells (SRBC) was examined. Injection of mice with ascites fluid from tumor-bearing mice markedly depressed the primary immune response of normal syngeneic mice challenged with SRBC. However, there was a preferential depression of the 19S IgM antibody response as compared with the 7S IgG response. Injection of ascites fluid shortly before secondary immunization of mice with SRBC also resulted in depressed IgM PFC responses but only a slight to moderate depression of IgG PFC. Treatment of mice with the ascites fluid before primary immunization had little if any effect on the secondary IgG PFC response, although the IgM response was moderately depressed. These results indicate that the immunosuppressive factor(s) present in the ascites fluid of mastocytoma-bearing mice has a differential effect on distinct classes of immunocytes. Those immunocytes or their precursors involved in formation of low efficiency 7S IgG antibody are more resistant to immunodepression. Such differences appear due to different sensitivities of cells involved in the immune response system.

Animals↗
PubMed1977

A direct hemolytic plaque assay on polylysine-coated coverslips for scanning electron microscopy of antibody forming cells.

A direct immunoplaque assay was utilized without agar or other semi-solid matrix for examining antibody secreting cells by scanning electron microscopy. For this purpose a polylysine procedure was used whereby 'charged' coverslips absorbed onto their surface an even monolayer of target sheep erythrocytes. Hemolysin secreting splenocytes derived either from mice immunized in vivo with SRBC or from normal or primed splenocytes immunized in vitro with the same antigen formed large numbers of hemolytic plaques on the RBC-coated polylysine treated coverslips. SEM examination of such plaque-forming cells revealed the presence of cells with the typical surface morphology of lymphocytes present in whole spleen cell suspensions. Many of the lymphocytes were covered with numerous microvilli while a small percentage were relatively free of such villi and exhibited a much smoother surface. Examination of lymphocytes secreting hemolytic antibody on polylysine coated coverslips sensitized with target erythrocytes thus permits the direct examination and analysis of surface morphologic features and also permits a direct comparison with other features revealed by light and fluorescent microscopy.

Animals↗
PubMed1977

Relationship between antigenic stimulation and increased splenic peroxidase levels during the immune response.

Immunization of mice with either soluble or particulate antigens induced a marked increase in peroxidase activity of spleen cell homogenates. Animals immunized with sheep erythrocytes showed maximum splenic peroxidase activity at 2 days. By the 4th day after immunization, when the hemolytic antibody plaque-forming cell response was maximal, peroxidase activity returned to normal levels. Increased splenic peroxidase activity also occurred in mice immunized with rabbit erythrocytes, as well as with rabbit serum or bovine serum albumin. No change in splenic peroxidase activity occurred in mice injected with syngeneic mouse erythrocytes or serum. Both glass-adherent spleen cell populations, morphologically consisting of 90 to 95% macrophages, as well as nonadherent cells, consisting of more than 90% lymphocytes by the same criteria, showed peroxidase activity. Immunization of mice with sheep erythrocytes resulted in an intracellular redistribution of the peroxidase activity among several distinct subcellular fractions prepared by differential centrifugation. Maximum redistribution occurred with granule-associated enzyme activity. A possible relationship between peroxidase activity with functional activity of lymphocytes and macrophages during humor immune responses seemed likely.

Animals↗
PubMed1977

Radiometric detection of bacteremia: requirement for terminal subcultures.

A radiometric procedure for rapid detection of bacteria in clinical blood specimens was utilized over a period of 1 year in this laboratory. Although in initial studies it was felt that all positive bacteremias would be detected by radiometric examination of cultures for 14CO2 evolution over a 7-day period, we found in the present study that a significant number of bacteria were not detected, except by blind subculturing on day 7 before discarding the culture sample. Microorganisms were detected in 490 individual specimens from 348 patients after examination of 6,200 individual blood specimens, both anaerobically and aerobically. All but 30 of the positive specimens were detected by the radiometric procedure, with an average detection time of 30.5 h. Thirty organisms, representing 6% of the total organisms isolated, were not detected by the BACTEC apparatus. The predominating organisms missed by the radiometric method were group D streptococci, both enterococcal and non-enterococcal species. These isolates represented two-thirds of the total number of organisms not detected by the radiometric procedure. A majority of bacteria detected only upon terminal subculture were isolates from a very small number of patients, suggesting that these organisms might have specific properties that preclude their detection by radiometric assay. Nevertheless, our study results indicate that it is essential that all radiometrically examined blood culture specimens be subcultured prior to discard in order to lessen the likelihood of missing a microbial pathogen.

Bacteria↗
PubMed1977

Detection of bacteriuria by automated electrical impedance monitoring in a clinical microbiology laboratory.

An apparatus capable of rapidly detecting changes in electrical impedance was utilized for the continuous monitoring of bacterial growth in routine urine specimens in a clinical laboratory. In a trial study, 200 clinical specimens analyzed by the electrical impedance method resulted in an average detection time of 2.5 h for 41 clinically significant specimens, whereas conventional methods for bacterial isolation required overnight culture. Those specimens positive by the electrical impedance monitoring but negative by conventional bacteriological methods accounted for less than 2% of the total number of positive specimens, whereas electrical impedance-negative but conventional culture-positive specimens accounted for ca. 4%. Electrical impedance apparatus in clinical microbiology laboratories could provide rapid screening of clinical urine specimens as well as accurate detection of bacterial growth.

Bacteria↗
PubMed1977

Rapid detection of bacterial growth in blood samples by a continuous-monitoring electrical impedance apparatus.

A growth detection method utilizing an automated apparatus capable of rapidly detecting bacterial growth by measuring changes of electrical impedance in bacteriological medium was utilized with "mock" blood cultures containing various gram-negative and gram-positive bacteria. Measurement of changes of electrical impedance was found to ba as accurate and comparable for time of growth detection as the radiometric method for detection of the same bacteria using mock blood cultures. In a limited clinical trial the use of the electrical impedance apparatus detected in 1 positive specimen from 40 clinical blood specimens as rapidly as by radiometric measurement. Both methods were considerably faster for detecting bacterial growth as compared with conventional culture methods. The selected species of gram-positive and -negative organisms tested were all detected by the electrical impedance method, including aerobes and anerobes. However, addition of 5% CO2 to the incubation atmosphere enhanced detection of gram-positive organisms.

Aerobiosis↗
PubMed1977

Cyclacillin-induced potentiation of Escherichia coli immunogenicity in vivo and in vitro.

The efficacy of cyclacillin as an antimicrobial agent against Escherichia coli was assessed in vivo in mice infected with low numbers of bacteria and compared to the relative effectiveness of the antibiotic against the same organisms in vitro. Treatment of mice with cyclacillin resulted in a rapid clearance of E. coli from the blood and their greater killing in the spleen and liver. Furthermore, a significantly higher antibody plaque response against E. coli developed in cyclacillin-treated mice than in untreated mice or in those given ampicillin. The increased immunogenicity of the E. coli in the antibiotic-treated mice appeared to be due to high levels of cyclacillin in the animals and rapid killing of the bacteria in vivo. In vitro experiments showed that injection of normal mouse peritoneal exudate macrophages which had been incubated with E. coli together with cyclacillin resulted in a greater immunogenicity of the bacteria than when the injection mixture was composed of E. coli which had been incubated alone or only with macrophages. These results suggest that the in vivo effectiveness of an antibiotic such as cyclacillin against a gram-negative organism such as E. coli may be due in part to an effect on the immunogenicity of the bacteria.

Ampicillin↗
PubMed1977

Differential effects of T-lymphocyte-derived soluble factor on virgin and primed B lymphocytes in vitro.

Cell-free supernatants from mixed leukocyte cultures derived from histoincompatible mouse strains markedly enhanced the in vitro immune response to SRBC by splenocytes from allogeneic mice. The supernatant factor or factors from allogeneic spleen cell cultures appeared to preferentially stimulate antigen-sensitized B lymphocytes, especially those involved in secondary IgG antibody formation. Furthermore, as shown in the present study, the enhancing supernatant factor or factors had no effect on the true primary in vitro immune response to Vibrio cholerae antigen. Normal spleen cells cultured in vitro without cholera vaccine failed to develop antibody-forming cells to this bacterial antigen, despite the presence of the enhancing factor. In contrast, the true secondary immune response to vibrios was markedly enhanced when allogeneic culture supernatants were added at the time of secondary immunization of cholera-primed splenocytes in vitro. Enhancement occurred both for 7S IgG and 19S IgM vibriolytic plaque-forming cells. It appears likely that T lymphocytes present among the allogeneic splenocytes interacting in vitro to histoincompatible antigens release a factor or factors that primarily affect antigen-primed B lymphocytes but also may influence other cells such as macrophages that are important in the immune response to particulate antigens.

Animals↗
PubMed1977

Immunocycte stimulation in vitro by nontoxic bacterial lipopolysaccharide derivatives.

Intact lipopolysaccharides (LPS), considered nonspecific enhancers of B cell responses, as well as nontoxic derivatives from Serratia marcescens LPS, were studied with regard to their ability to stimulate in vitro immune responses to a T-dependent antigen, sheep erythrocytes. Intact LPS, at a dose of 10 to 50 microgram, consistently enhanced the in vitro anti-SRBC immune response by normal splenocytes. The LPS also increased the background PFC response to SRBC in nonimmunized cultures. A chemically detoxified preparation derived from LPS (Mex B) had no stimulatory activity in vitro. A completely nontoxic, relatively small m.w., polysaccharide-rich preparation (PS), free of detectable lipid and protein, was stimulatory in vitro and at a dose of 10 microgram resulted in a 40 to 70% enhancement of the anti-SRBC response. The PS also stimulated an enhanced background response to SRBC as well as several other RBC species in nonimmunized cultures. PS had no mitogenic effect in vitro since addition of this bacterial derivative failed to stimulate thymidine incorporation into mouse splenocytes, as occurred with the intact LPS. The use of nontoxic preparations from gram-negative bacterial LPS for dissecting the stimulatory vs antigenic properties of bacterial products provides a model system for determining the role of a mitogenic stimulus in B cell activation.

Animals↗