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Biomedical subjects

T Kamiyama

Publications and source records attributed to T Kamiyama.

At least 163 records · Page 9Linked to original sources
PubMed1983

Effect of Toxoplasma infection on the sensitivity of mouse thymocytes to natural killer cells.

Thymocytes from mice 2 weeks after infection with Toxoplasma gondii resisted natural killer (NK) cell-mediated cytolysis in contrast to the high sensitivity of normal mouse thymocytes. The infected mouse thymocytes also failed to form conjugates with effector cells and to compete for cytolysis of NK sensitive targets. These effects were mediated, at least in part, by interferon-gamma because normal thymocytes became NK insensitive after incubation in the infected mouse serum which contained significant amount of interferon-gamma, and pH 2 treatment of the serum abolished the effect. An alternate possibility for the reduced NK sensitivity of the infected mouse thymocytes was the elimination of NK-sensitive cells from the thymus, since histopathological studies showed marked atrophy and clearance of NK-sensitive thymocytes in the cortex of thymuses of infected mice. Although T. gondii induced augmentation followed by suppression of the host splenic NK activity, it seems unlikely that this altered NK activity was responsible for the lowered NK sensitivity of the thymocytes.

Animals↗
PubMed1983

Species and strain differences in sensitivity to Toxoplasma infection among laboratory rodents.

Different susceptibilities to Toxoplasma infection were shown among various inbred and outbred laboratory rodents. On the basis of several criteria, the animals can be divided into three groups: (i) highly sensitive (S) mice, Syrian hamsters and Chinese hamsters; (ii) moderately sensitive (M) Mongolian gerbils and mastomyses ; and (iii) resistant (R) rats and Korean striped field mice. S and M hosts supported intraperitoneal growth of the parasites and died of acute infection. M hosts showed prolonged time to death and low fatality as compared with S hosts. Some R hosts died only when they had received an extremely large size of inoculum, accompanying poor intraperitoneal proliferation of the parasite. WM/Ms and WKY rats markedly resisted the infection. These hosts were considered to be useful models for studying infection of and immunity to toxoplasmosis.

Animals↗
PubMed1982

Augmented followed by suppressed levels of natural cell-mediated cytotoxicity in mice infected with Toxoplasma gondii.

The cytotoxic activity of effector cells from mice infected with Toxoplasma gondii was tested in a 4- to 5-hr (51)Cr release assay, using RL [vertical male] 1 and YAC-1 target cells. They showed enhanced cytotoxicity with a peak on the 3rd day postinfection followed by suppression with a peak on the 12th day. The cytotoxicity seemed to be exhibited by natural killer (NK) cells because: (i) pretreatment of the effector cells with antiasialo GM(1) or antiasialo GM(2) plus complement abolished the cytotoxic activity; (ii) the altered cytotoxicity levels were also induced in nude mice; and (iii) the activity was elicited by nonadherent-nonphagocytic cells. The alteration occurred simultaneously in various lymphoid organs with a similar profile. Neither spleen nor bone marrow cells of 12-day-postinfected mice inhibited NK activity of uninfected mice. Culture fluids of the infected mouse spleen and bone marrow cells did not affect the normal mouse NK activity. The proportion of effector cells capable of binding to target cells was constant during the infection. There was no positive correlation between NK activity and serum interferon level; i.e., interferon was detected in the serum of 12-day-postinfected mice but not in that of 3-day-postinfected or uninfected mice. Passively administered interferon or polyinosinic-polycytidylic acid could not restore the suppressed NK activity of 12-day-postinfected mice. Moreover, in vitro treatment of spleen cells from 12-day-postinfected mice with interferon failed to restore the suppressed NK activity. These results suggested that after toxoplasma infection, defective sensitivity to interferon was induced in NK precursor cells, and differentiation to functionally active NK cells might be blocked.

Animals↗
PubMed1982

Natural killer cell activities of several inbred strains of the guinea pig and their susceptibilities to rabbit antiserum directed to guinea-pig brain tissue.

Natural killer (NK) cell activities of spleen and peripheral blood leukocytes from several inbred guinea-pig strains, established in this Institute, were assessed in an 18-hr 51Cr-release assay. As target cells in the NK assay, a human myeloid cell line, K562, appeared to be the most suitable among several cultured cell lines tested. Intensities of cytolysis were different from strain to strain, but generally high in JY-2, JY-4 and JY-10 and low in JY-1. Treatment of the effector cells with rabbit anti-guinea-pig brain tissue serum plus complement reduced the NK activity, whereas treatment with rabbit anti-guinea-pig thymocyte serum, or rabbit anti-asialo GM1 serum, plus complement showed no significant effect on the NK activity.

Animals↗
PubMed1980

The molar combining ratio of anti-albumin Fab' fragments to homologous and heterologous serum albumins.

The number of antibody combining sites on bovine (BSA), goat (GSA) and sheep (SSA) serum albumins was studied using rabbit and chicken antibodies. In homologous reactions, the profiles of quantitative precipitations with chicken antibody were similar to those with rabbit antibody reported previously (12), and the antigenic valence in the extreme antibody excess zone was found to be 6-7 for each albumin. The univalent Fab' fragments of rabbit and chicken antibodies were prepared. The stoichiometry of the soluble complex formed with the Fab' fragment and fluorescence labeled albumin was analyzed by gel filtration, and the number of Fab' fragment molecules capable of binding to an albumin molecule was estimated. In a homologous reaction with both rabbit and chicken Fab' fragments, the Fab' to albumin combining ratio revealed from the molecular weight of the soluble complex was 14:1. In the heterologous reactions, the combining ratio was 5:1 for rabbit Fab' fragments to BSA, and 9:1 for chicken Fab' fragment to BSA. From the heterologous reactions between GSA and SSA, it was demonstrated that the combining ratios were 10-11:1 with rabbit Fab' fragment and 11-13:1 with chicken Fab' fragment.

Antibodies, Anti-Idiotypic↗
PubMed1978

Tumor-specific skin-reactive antigen solubilized from a syngeneic guinea pig liposarcoma by 3M potassium chloride.

Tumor-specific and skin-reactive antigen of a syngeneic liposarcoma (H-10) of Hartley/F guinea pig was solubilized with 3M potassium chloride and purified by precipitation with 2M ammonium sulfate, followed by Sephadex G-200 gel filtration. The antigenic activity of 7 fractions obtained was estimated by the delayed-type skin reaction elicited in syngeneic animals immunized with H-10 cells admixed with BCG. Accurate relative activity of the fractions comparable to the skin reaction elicited by living H-10 cells was calculated by the parallel line assay method in which the dose-response curves of the fractions are compared with that of living cells. About 30 approximately 50 microgram protein of the 3 fractions eluted slowly from the Sephadex column elicited the skin reaction equivalent to that elicited with 1 X 10(6) of living H-10 cells. Tumor-specific skin reactivity per microgram protein of these 3 fractions was roughly 20 approximately 40 times higher than that of lyophilized cells.

Animals↗