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Biomedical subjects

H Hahn

Publications and source records attributed to H Hahn.

At least 271 records · Page 15Linked to original sources
PubMed1979

Peritoneal exudate T lymphocytes with specificity to sheep red blood cells. I. Production and characterization as to function and phenotype.

T lymphocytes which mediate DTH reactions to sheep red blood cells (SRBC) in mice enter casein-induced peritoneal exudates from which they can be recovered and assayed in a passive transfer system. Peritoneal exudates need not contain specific antigen for inducement of T-cell immigration. The amount (or biological activity) of DTH-transferring peritoneal exudate lymphocytes is enhanced by the previous use of immune modulating agents, such as cyclophosphamide (Cy) (200 mg/kg 2 days prior to sensitization), or BCG (10(7) live organisms i.v. 14 days prior to sensitization). SRBC-specific peritoneal exudate lymphocytes phenotypically are Thy 1+ and Ly 1+, 2-. In vivo, peritoneal exudate T cells from Cymodulated donors persist in circulation for a short period only and are subject to the suppressive mechanisms acting in anergic mice. Cells from BCG-plus-Cy-modulated donors, on the other hand, persist in circulation for a longer period and appear to be less susceptible to immune suppression.

Animals↗
PubMed1979

Peritoneal exudate T lymphocytes with specificity to sheep red blood cells. II. Inflammatory helper T cells and effector T cells in mice with delayed-type hypersensitivity and in suppressed mice.

Peritoneal exudate cells were induced in mice 4 days after immunization with SRBC. A low dose of SRBC (10(6) i.v.) caused T lymphocytes to appear in inflammatory exudates. These cells, not only transferred DTH reactions, but also functioned as helper T cells in antibody production after transfer to syngeneic nu/nu recipient mice. After a high dose of SRBC (10(9) i.v.), very few helper T cells and no DTH transferring T cells were found in inflammatory exudates, although they were present in the spleen. It is postulated that T cells mediating DTH reactions and helper T cells behave similarly as far as those dose dependency of appearance in inflammatory exudates is concerned. A high dose of sensitizing antigen causes retention of helper and effector T cells in the spleen, in this way favouring antibody formation; low doses of antigen allow them to leave the spleen, thus favouring mediation of DTH reactions in the periphery.

Animals↗
PubMed1978

The effect of dextransulfate 500 on the pathogenesis of herpes simplex virus infections in weanling mice.

Intraperitoneal (i.p.) injection of Dextran Sulfate (D.S.) 500 during a limited period of time influences the course of herpes simplex-virus-infections. D.S.500 was found to reduce the resistance of mice for some herpes simplex-virus strains (Len, L3--2s, Haase) if given between 16 hours and 2 hours after i.p. infection. The decrease of resistance could be correlated with an increase of the virus content of liver, spleen, brain and spinal cord. Injection of herpes simplex-virus-specific immune serum counteracted the effect of D.S.500 on the course of infections. Conversely, D.S.500 increased the resistance of mice to another group of herpes simplex-viruses (strains D-316, Thea, DD), if given 3 to 8 hours before infection. These effects are ascribed to a special interaction of D.S.500 with macrophages and probably other virus-susceptible cells of the peritoneal cavity and elsewhere with a resulting counteraction to the virus infection.

Adsorption↗
PubMed1978

Fracture healing in weight-bearing and nonweight-bearing bones.

Animal models demonstrated the differences in the process of fracture healing in weight-bearing and nonweight-bearing bones. Canine rib fractures regained strength properties rapidly; in canine radial fractures the return to normal stiffness levels was primary. The structural differences in fracture healing are probably functional and due more to biologic reorganization than to any measurable change in the biochemical components of the callus.

Animals↗
PubMed1978

[Gram-positive bacteria as adjuvants (author's transl)].

Gram-positive bacteria or their constituents influence the immune response in various ways. For instance: Listeria monocytogenes cellwall fraction acts as B-cell mitogen, in this way enhancing a humoral immune response. Corynebacterium parvum acts as a macrophage stimulant evoking maximum macrophage activation. BCG, among other things, leads to an enhancement of a T-cell response to unrelated antigens. The hypothetical therapeutic consequences are discussed.

Adjuvants, Immunologic↗
PubMed1977

[Delayed type hypersensitivity and Immunity (author's transl)].

Delayed type hypersensitivity is a T-cell-mediated phenomenon. It is characterized by the following features: a) development within 24-72 h after antigen challenge in sensitized individuals, b) perivascular infiltration by mononuclear cells at the inflammatory site, c) transfer by lymphocytes, but not by serum. Delayed type hypersensitivity occurs during infections with facultatively intracellular bacteria and certain viruses, tumor diseases and rejection of transplanted foreign tissue. This article samples evidence that delayed type hypersensitivity is an outward phenomenon indicating the presence of specific T-cells and mononuclear phagocytes, both acting together to produce local immunity which results in the elimination or containment of the noxious agent.

Bacterial Infections↗
PubMed1976

Quantitative contributions of IgG, IgM and C3 to erythrophagocytosis and rosette formation by peritoneal macrophages, and anti-opsonin activity of dextran sulfate 500.

In vitro phagocytosis by guinea pig peritoneal macrophages of immune complexes (EA) was shown to be dependent on IgG antibody in a dose-dependent fashion. C3b enhanced phagocytosis of EA at limited IgG antibody concentrations only. When IgM antibody was used for sensitization of sheep red blood cells (SRBC), phagocytosis and rosette formation did not occur in the absence of bound C3. The polyanion, dextran sulfate 500 (DS), was shown to depress both rosette formation and phagocytosis of EAIgG, C1423 and EAIgMC1423, as well as immune adherence of human group 0 erythrocytes and hemolytic activity of C3. This effect of DS was seen only when it was actually present in the incubation medium.

Animals↗
PubMed1976

Inhibition of acetate and propionate formation upon aeration of resting cells of the anaerobic Propionibacterium shermanii: evidence of the Pasteur reaction.

When resting cell suspensions of the anaerobic P. shermanii were brought to an oxygen concentration of 0.64 mumoles/ml, acid formation was completely inhibited. The cells started to respire on the propionic acid previously accumulated furing anaerobiosis. Glucose consumption was concomitantly decreased to about 60 percent of the rate during anaerobiosis. As the viability of the cells was not affected by the transition to aerobic conditions, the changes observed upon aeration were ascribed to the regulatory properties of the Pasteur reaction. Damage inflicted by oxygen was encountered in the rapid inactivation of propionate respiration. This damage outlived the time of oxygenation, and was manifested during the subsequent anaerobiosis in the decreased activity to form propionate. This indicates that oxygen may inactivate one (or more) enzyme(s) involved in the metabolism of propionate. The viability of cells in buffer, and glucose-containing buffer, was found to be only insignificantly decreased by oxygen in the range from 0 to 500 mumoles of oxygen per g of wet cells.

Acetates↗
PubMed1976

Opsonizing activities of IgG, IgM antibodies and the C3b inactivator-cleaved third component of complement in macrophage phagocytosis.

Phagocytosis of SRBC by guinea-pig peritoneal macrophages is enhanced by opsonizing IgG antibody alone. IgM antibody requires the presence of bound C3. Treatment of C3b coated SRBC with purified C3b inactivator (yielding EAIgM C1423d) does not reduce attachment to, and phagocytosis by, peritoneal macrophages. This finding suggests the existence of a C3d receptor on peritoneal macrophages. EC43b intermediates which have been produced by removing IgM antibody by mercaptoethanol treatment and by subsequent removal of C1 and C2, are phagocytosed despite the absence of IgM antibody. Furthermore, treatment of EC43b with C3b inactivator does not change phagocytosis. Thus, IgM antibody does not appear to be a necessary prerequisite for the stimulation of phagocytosis, C3b or C3d alone being sufficient.

Animals↗
PubMed1976

[Use of Nessler's reagent for recognition of lysine, ornithine, and arginine decomposition by gramnegative fermentative bacteria (author's transl)].

The reactions of lysine, ornithine and arginine decomposition are often difficult to read in Falkow's medium because either the decolorization of the indicator or the lack of sharp colour differences between positive and negative reactions. In such cases Nessler's reagent may be a useful aid. A volume of about 0.2 ml is added to the cultures after 4 days incubation through the mineral oil layer by means of a pipette. A positive reaction is indicated by an immediate white precipitation in case of lysine and ornithine decarboxylation, and a white or brownish precipitate which indicates arginine decomposition. A delayed opacity should be regarded as a negative reaction. Only unequivocal reactions should be considered. The specificity of the reactions was tested with pure substances of compounds which are formed by the decomposition of lysine, ornithine and arginine. Further studies of bacterial cultures in Falkow's medium and in a synthetic, amino acid containing medium without peptone gave identical results and showed that peptone derivates do not cause a false positive reaction with Nessler's reagent (Table 1). Comparative studies on 605 strains of Enterobacteriaceae and Vibrio in Falkow's medium with and without added Nessler's reagent gave corresponding results except some strains of Escherichia coli and Citrobacter freundii with different arginine reactions (Table 2). Strains of these species mostly decolorized the indicator thereby hindering the recognition of either a true positive or a true negative reaction. In these cases, however, the results obtained after addition of Nessler's reagent corresponded closely to the percentage of positive reactions cited in the literature.

Arginine↗
PubMed1975

Macrophage inhibiting activity in serum and central lymph of Listeria-immune mice.

Serum and central lymph from mice immunized with live Listeria monocytogenes six days previously and boostered four hours before collection exerted significant inhibition of macrophage migration in vitro. It is concluded that lymphokines or lymphokine-like products of the cellular immune reaction are released in vivo and are possibly instrumental in the generation of acquired cellular antibacterial immunity.

Animals↗
PubMed1975

Requirement for a bone marrow-derived component in the expression of cell-mediated antibacterial immunity.

Mice were X irradiated with 400 R and 1 week post-irradiation were found to be unable to develop antilisterial immunity after active or passive immunization with immunologically committed spleen lymphocytes from Listeria-immune donors. This consequence of irradiation disappeared spontaneously within 21 days of exposure to X rays. Mice irradiated with as much as 900 R could be passively protected by immunologically committed lymphoid cells from Listeria-immune donors 10 days after irradiation if they had been given normal bone marrow cells on the day or irradiation. It is concluded that, in addition to immunologically committed lymphocytes, a second cellular component is needed for the expression of antibacterial immunity. This second component is bone marrow derived.

Animals↗