Genetic factors in the stimulation of T cell responses against ectromelia virus-infected cells: role of H-2K, H-2D, and H-2I genes.
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Animals↗
Biomedical subjects
T Pang
Publications and source records attributed to T Pang.
The use of H-2 mutants as models for the study of T cell activation.
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Animals↗
Regulation of the T-cell response to ectromelia virus infection. I. Feedback suppression by effector T cells.
Spleen cells and serum from mice immunized with ectromelia virus suppressed the immune response to infectious virus when transferred intravenously into recipient mice given an immunizing virus dose. The suppression was reflected in decreased cytotoxic T-cell activity directed against H-2 compatible virus-infected target cells in the spleens of recipients. Suppression was observed when immune cells or serum were transferred 1-2 h or 1 day after immunization of recipients, but not 2 days after, and was maximal when 6-day immune spleen cells were used as suppressor cells. H-2 compatibility between donor and recipient mice was necessary for suppression to be expressed. Use of recombinant mice showed that I-region compatibility was neither sufficient nor necessary, and that D-region compatibility was sufficient. Specificity of suppression was suggested by the finding that cells and serum from mice immunized with Listeria monocytogenes, a bacterium, had no suppressive activity on the antiviral response. Anti-theta treatment eliminated the ability of immune cells to suppress, and the suppressive effect was not markedly dose-dependent with respect to both cell dose and virus dose under the conditions employed. Virus levels in the spleens of recipients were significantly reduced after injection of immune cells. Adult thymectomy had no effect on the primary immune response to ectromelia virus infection, thus indicating no role for T1 cells in the suppressive mechanism. The results obtained therefore suggested that suppression in this system was due to effector T cells which triggered clearance of virus (and thus, of virus-induced antigens) necessary for the induction of precursors of effector T cells, and that this simple feed-back mechanism normally plays an important role in the regulation of the primary immune response to ectromelia infection at the level of precursor induction. The existence of other postinduction regulatory mechanisms, however, is unknown and under investigation.
Animals↗
Cooperation between mouse T-cell subpopulations in the cell-mediated response to a natural poxvirus pathogen.
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Animals↗
Cytotoxic T cells in the peritoneal cavity of mice infected with ectromelia virus.
Peritoneal exudate cells from mice infected with ectromelia virus were cytotoxic for virus-infected target cells as measured in a 51Cr release assay. Cytotoxic activity seemed to be T cell-dependent as it was largely abolished by treatment with anti-theta serum and complement but was not impaired by macrophage depletion. The kinetics of development of cytotoxicity in the peritoneal cavity lagged behind spleen cytotoxicity by 1-2 days. Peak activity in peritoneal cells was present about 6 days after intravenous infection with virus. These studies suggest that macrophages present in the free peritoneal cell populations of ectromelia-infected mice are not cytotoxic for virus-infected target cells. The effect of macrophages in virus clearance is therefore likely to be due to phagocytic rather than cytotoxic effects.
Animals↗
"Physiological interaction" does not explain the H-2 requirement for recognition of virus-infected cells by cytotoxic T cells.
B10.A (H-2Kk, H-2Dd) ectromelia-immune T cells from secondary responses in vitro were protent killers of both infected L929 (H-2Kk H-2Dk) and infected P-815 (H-2Kd, H-2Db) target cells. Specific competition with unlabelled targets showed that two separate T cell subsets were responsible for lysis of infected L929 and infected P-815 cells. One hypothesis to account for this (a form of "physiological interaction") is that T cells which kill one target e.g. infected L929) display only one out of two possible self-complementary recognition structures, in this example the H-2Kk alloantigen, not H-2Dd, whereas T cells that lyse infected P-815 targets display only H-2Dd, not H-2Kk. This hypothesis was tested and seems untenable because of the following results: A.TH (H-2Ks, H-2Dd) ectromelia-immune, secondary cytotoxic T cells which killed infected SJL/J (H-2Ks, H-2Ds) targets were themselves inactivated by pre-incubation with SJL/J cytotoxic T cells generated in one-way mixed lymphocyte reaction (MLR) against BALB/c (H-2Kd, H-2Dd). A.TL (H-2Ks, H-2Dd) ectromelia-immune secondary cytotoxic T cells which killed infected BALB/c targets were themselves inactivated by BALB/c cytotoxic T cells generated in MLR against SJL/J. Thus, virus-immune T cells which lyse infected targets by virtue of shared H-2K are also displaying H-2D alloantigen, and vice versa.
Animals↗
The role of adherent cells in the secondary cell-mediated response in vitro to a natural poxvirus pathogen.
The role of adherent cells in an in vitro secondary response to ectromelia virus infection was investigated. Spleen cells from ectromelia-primed mice ("responder" cells) depleted of adherent cells by either carbonyl iron treatment, adherence to plastic or passage through cotton wool columns had a markedly decreased capacity to produce a secondary response, as indicated by decreased T cell-mediated cytotoxicity against virus-infected target cells, when cultured with virus-infected "stimulator" cells. The secondary response was restored by the addition of peritoneal cells from either normal or ectromelia-immune mice. Small numbers of peritoneal cells completely reconstituted the response within a certain dose range but larger numbers produced a marked inhibition of the response. Spleen cells were less effective in restoring the response. The peritoneal cells were not merely acting as additional, infected "stimulator" or antigen-presenting cells, since they could be added as late as 3 days after culture. Reconstituting activity was not affected by pretreatment with anti-theta serum and complement and cell separation studies showed that the activity was associated mainly with Ig-negative cells and that the active cell probably bears Ia antigens on its surface. These results indicate that the adherent cells involved are probably macrophages and that they act non-specifically to produce optimum conditions for the specific response of T cells.
Animals↗
The cell-mediated immune response to ectromelia virus infection. Secondary response in vitro: specificity, nature of effector and responder cells and requirements for induction of antigenic changes in stimulator cells.
An in vitro culture method was used to study secondary cell-mediated responses to ectromelia virus infection in mice. Infected, syngeneic spleen cells or peritoneal cells were efficient "stimulator" cells when cultured with "responder" cells obtained from mice infected with ectromelia 4-6 weeks previously. The kinetics of generation of cytotoxic cells in cultures were determined; a peak occurred on days 4-5. A separation procedure performed on the cytotoxic cells showed that activity was associated mainly with the Ig-negative subpopulation (T cell-rich) and that H-2 compatibility between cytotoxic cells and target cells was required. The secondary response was virus-specific, at the level of both induction and target cell lysis, at least so far as ectromelia and lymphocytic choriomeningitis (LCM) viruses are concerned. Seperation of responder cells prior to culture showed that a potent secondary response was generated with the Ig-negative (T cell-rich) subpopulation and only a weak response was observed when the responder cells were Ig-positive (rich in B cells). Infected stimulator cells did not appear to secrete significant amounts of soluble antigen into the medium over 4 days of culture. Thus, antigenic patterns effective in memory T cell stimulation may be largely associated with the surfaces of infected cells.Pretreatment of ectromelia virus with UV- or gamma-irradiation did not impair its ability to induce antigenic changes in stimulator cells. Stimulator cells treated with UV-or gamma-irradiated virus for 1 h and then immediately with pactamycin to inhibit further viral protein synthesis and replication were efficient stimulators, thus indicating that antigenic changes are induced very rapidly on the surface of stimulator cells after uptake of virus. These treatments are being used to further characterize the cellular requirements in the stimulator population.
Animals↗
Effect of cell dose and dose of infectious agent on expression of protection against Listeria monocytogenes and Ectromelia virus in cell transfer models.
Two parameters (immune cell dose and dose of infectious agent) influencing the expression of protection by transferred immune spleen cells in Listeria monocytogenes and ectromelia virus infection in mice were investigated. First, when recipient mice were infected with a constant dose of ectromelia virus, a linear relationship between log(10) cells transferred and the protection obtained expressed as log(10) decrease in virus plaque-forming units per spleen was obtained, as has been described previously for the Listeria system. Second, the detectable protection was greatly affected by the number of viable bacteria or virus plaque-forming units relative to the number of transferred cells. An otherwise very effective number of transferred immune cells became ineffective when too great a dose of infection was used. Mouse strain differences could also have influenced the results. The impact of these and other parameters on the experimental outcome and its interpretation are discussed.
Animals↗
Genome size variation among recent human isolates of Salmonella typhi.
We performed genome size estimation of 17 recent human isolates of Salmonella typhi from geographically diverse regions using pulsed-field gel electrophoresis (PFGE) after digestion of chromosomal DNA with restriction endonucleases XbaI (5'-TCTAGA-3'), AvrII (5'-CCTAGG-3') and SpeI (5'-ACTAGT-3'), and summation of the sizes of restriction fragments obtained. All 17 isolates had circular chromosomes, and genome sizes differed by as much as 959 kb, ranging from 3,964 to 4,923 kb (mean genome size = 4,528 kb). The data obtained confirm the usefulness of PFGE in studies of bacterial genome size and are in agreement with recent results indicating considerable genetic diversity and genomic plasticity of S. typhi. The variation in genome sizes noted may be relevant to the observed biological properties of this important human pathogen, including its virulence.
Base Sequence↗
Outbreak of Salmonella enteritidis gastroenteritis: investigation by pulsed-field gel electrophoresis.
OBJECTIVE: Pulsed-field gel electrophoresis (PFGE) was used to investigate an outbreak of gastroenteritis caused by Salmonella enteritidis. The outbreak occurred among university undergraduates who consumed contaminated food. METHOD: Molecular typing was done by analyzing DNA band patterns of isolates of S. enteritidis after digestion of chromosomal DNA with infrequently-cutting restriction endonucleases XbaI, AvrII, and SpeI and separation of DNA fragments using PFGE. RESULTS: Twenty-nine outbreak isolates of S. enteritidis had identical or highly similar PFGE patterns, whereas different PFGE patterns were observed among three epidemiologically unrelated isolates obtained during the same period. CONCLUSION: The data obtained confirm the value of PFGE in epidemiologic investigations of outbreaks caused by S. enteritidis.
Adult↗
Sequence variations of the late upstream region of HPV16 in cervical intraepithelial neoplasm and invasive carcinoma.
HPV16 is the most common type of human papillomavirus (HPV) seen in cervical squamous cell carcinoma. A 78-bp promotor element at nt 4118-4196 called late upstream region (LUR), critical for the expression of late genes, has been identified recently. Late genes encode viral capsid proteins that coat viral DNA to form particles and serve as antigen. To elucidate whether there are any sequence variations within LUR of HPV16 and any difference of these sequence variations between cervical invasive squamous cell carcinoma (CIC) and cervical intraepithelial neoplasia (CIN), we sequenced HPV16 LUR from 50 cases of HPV16-positive CIC and CIN. We found that variation frequency in the late upstream region ranged from 0 to 4.2 except for two cases in which variation frequency was as high as 22.8%. Eight of 24 CINs and 17 of 26 CICs contained two or more variations (33% vs. 65%, P < 0.025). The results suggested that the sequence variations occurred more often in LUR of HPV16 than in other regions of HPV16 and the variations in HPV16 LUR might play a role in the process of carcinogenesis of cervical carcinoma.
Base Sequence↗
Delayed-type hypersensitivity: probable role in the pathogenesis of dengue hemorrhagic fever/dengue shock syndrome.
The hypothesis presented proposes the involvement of a systemic form of a delayed-type hypersensitivity reaction in the pathogenesis of dengue hemorrhagic fever/dengue shock syndrome. It envisages the activation of sensitized T lymphocytes during a secondary infection by viral antigen present on the surfaces of mononuclear phagocytic cells. These antigen-activated T cells then release a variety of biologically active chemical mediators (lymphokines), which then produce the symptoms of shock and hemorrhage seen in cases of dengue hemorrhagic fever/dengue shock syndrome.
Capillary Permeability↗
Molecular analysis of Salmonella paratyphi A from an outbreak in New Delhi, India.
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Disease Outbreaks↗
Immunohistochemical and DNA sequencing analysis on human mismatch repair gene MLH1 in cervical squamous cell carcinoma with LOH of this gene.
BACKGROUND: The human MLH1 gene (hMLH1) is one of the DNA mismatch repair genes. Defects in these genes are believed to be the underlying cause of microsatellite instability (MSI). MSI has been demonstrated in many human cancers such as colon cancer and some female-specific tumors. The hMLH1 gene can be inactivated by genetic mutation or by hypermethylation of its promoter region, which often causes cessation of hMLH1 protein production. We were prompted by our previous finding of 43% of cervical cancers and their precursors with a loss of heterozygosity (LOH) of the hMLH1 gene to investigate whether it is inactivated during the carcinogenesis of cervical cancer. MATERIALS AND METHODS: hMLH1 protein production was assessed by immunohistochemistry, and nucleotide sequence analysis were performed on all exons of the hMLH1 gene. RESULTS: In 11 cases of invasive cervical cancer, among which 7 had LOH of the hMLH1 gene, immunohistochemistry provided no evidence for cessation of hMLH1 protein production. In addition, no mutations were found in any of the 19 hMLH1 gene exons. CONCLUSIONS: The activity of hMLH1 gene might not be disturbed in the development of cervical cancer although a proportion of the cases had lost one of its hMLH1 gene copies.
Adaptor Proteins, Signal Transducing↗
Role of molecular typing in an outbreak of Salmonella paratyphi A.
During the post monsoon season of 1996 an outbreak of human Salmonellosis caused by Salmonella serovar-paratyphi A occurred in New Delhi and had continued for over 2 months. A total of 36 clinically diagnosed enteric-fever cases were reported during this outbreak. The isolates were compared following their characterisation by biotyping, antibiogram-analysis, plasmid-profiling and IS200 probing, to study the relatedness in order to delineate a common source. The study included representative strains from both outbreak (15) and sporadic (7) cases for comparative analysis. Biotyping, antibiogram, whole cell protein-analysis and plasmid-profiling could not discriminate sporadic cases from outbreak strains, suggesting that a single clone/type (PT-1) may be prevalent in our region. In contrast, molecular-typing using IS200-probing revealed 2 clonally related strains circulating during the outbreak, as compared to the unrelated sporadic strains which exhibited considerable genetic diversity. Molecular analysis by IS200-probing, helped to assign an index case which provided a history of later outbreaks, since paratyphi A was repeatedly cultured in later outbreaks also. The study also suggests that genetic rearrangements can occur during the emergence of outbreaks. It reaffirmed the usefulness of IS200-probing in epidemiological investigations of Salmonella enterica serovars.
Bacterial Typing Techniques↗