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D T Yu

Publications and source records attributed to D T Yu.

At least 19 recordsLinked to original sources
PubMed1991

The nucleotide and deduced amino acid sequence of the cationic 19 kDa outer membrane protein OmpH of Yersinia pseudotuberculosis.

The OmpH proteins of enteric bacteria are recently described, small (16 kDa), cationic outer membrane proteins. Because a Yersinia pseudotuberculosis cell envelope protein of this size has been found to cross-react serologically with the human histocompatibility antigen HLA-B27 (B*2701), the sequence of Y. pseudotuberculosis OmpH was determined by sequencing the gene region which encodes mature OmpH. A protein consisting of 143 amino acid residues was found. It was 96% homologous with the OmpH of Y. enterocolitica and 62% homologous with that of Escherichia coli. Two separate OmpH regions had sequence similarity with B*2701; they were identical in both Yersinia species.

Amino Acid Sequence↗
PubMed1991

Analysis of the molecular mimicry between HLA-B27 and a bacterial OmpA protein using synthetic peptides.

In spite of a lack of sequence 'homology' between HLA-B27 and the bacterial OmpA outer membrane proteins, they both react with the Ye-2 monoclonal anti-HLA-B27 antibody. The Ye-2 antibody also reacted positively in ELISA with a synthetic peptide derived from the segment spanning residues 63-84 of B*2705. The critical peptide residues were determined by testing first with overlapping peptides, followed by a replacement set made according to the determined epitope. The results were compared with those with overlapping eight mers made to span a carboxyl fragment of the Escherichia coli OmpA protein. They indicate the reason why Ye-2 reacts with both sets of peptides is because it has a preference for polymers of arginine.

Amino Acid Sequence↗
PubMed1990

Epitope mapping of an HLA-B27 monoclonal antibody that also reacts with a 35-kD bacterial outer-membrane protein.

Ye-3 is an HLA-B27-specific murine monoclonal antibody recognizing the heat-modifiable protein of Enterobacteriaceae. Here we used recombinant hybrid molecules between the HLA-B7 and HLA-B27 antigens to delineate the epitope recognized by Ye-3. Results of these experiments indicated that the segment of HLA-B*2705 spanning residues 77-81 was critical to the reactive epitope. It is known to be a major serological and functional recognition site of HLA-B*2705 and our data give support for its involvement also in the serological cross-reactivity with bacterial antigens.

Alleles↗
PubMed1990

Demonstration of shared epitopes between bacterial proteins and HLA class-I proteins using monoclonal antibodies.

Monoclonal antibodies were used to identify the presence of epitopes on bacterial proteins which are cross-reactive with HLA-B27. Anti-HLA-B27 monoclonals, B27M2 and YE-2 reacted with a major protein of approximately 35 kDa, which was found to be OMPA. On some strains a 19 KDa protein was also seen. Anti-Shigella flexneri monoclonals were also developed which reacted with a 36 kDa protein and a 19 kDa protein. The 36 kDa protein was OMPF. These antibodies also reacted with a synthetic peptide representing amino acids 63-83 of the B*2705 sequence. These results support a potential role for molecular mimicry in the spondyloarthropathies.

Antibodies, Monoclonal↗
PubMed1990

A ribosomal protein of Yersinia pseudotuberculosis having partial epitope identity with HLA-B27.

The phenotype HLA-B27 is common in patients who develop reactive arthritis after having an infection. One hypothesis concerning the pathogenesis of reactive arthritis is that molecular mimicry between HLA-B27 and certain bacterial components might be involved. It is known that an infection with Yersinia is commonly associated with reactive arthritis in B27 positive patients. Therefore, we were interested to investigate whether cross-reactivity between Yersinia and HLA-B27 exists. A gene library of Yersinia pseudotuberculosis was created in the plasmid vector pUC13. One of the resulting clones contained a gene encoding an intracytoplasmic protein that seems to have partial epitope identity with HLA-B27. It reacted in western blot. ELISA and immunoprecipitation with three different HLA-B27 specific monoclonal and polyclonal antibodies of the IgG and IgM class. However DNA-sequencing of the cloned Yersinia gene and the predicted amino acid sequence revealed only a very remote similarity with HLA-B27 in the primary structure. Instead, an extremely high degree of similarity with the ribosomal protein L4 of the S10 operon of Escherichia coli was identified indicating that the protein encoded by the cloned Y. pseudotuberculosis gene is a corresponding ribosomal protein.

Amino Acid Sequence↗
PubMed1979

Ia determinants on stimulated human T lymphocytes. Occurrence on mitogen- and antigen-activated T cells.

Human T-cell blasts were generated by stimulation with mitogens and antigens. A proportion of these blasts expressed Ia antigens detectable by immunofluorescence with both allo- and hetero-antiserums. The maximal expression of Ia antigens was delayed and usually occurred after the peak of blastogenesis. Among the three mitogens used, pokeweed mitogen (PWM) was most effective in giving a high percentage and intense Ia staining of T-cell blasts. Phytohemagglutinin and concanavalin A blasts gave weaker and lower percentages of Ia staining. Activation by alloantigens and soluble antigens such as tetanus toxoid and purified protein derivative resulted in Ia expression on T cells comparable to PWM stimulation. Depletion of Ia+ cells from freshly isolated T cells with anti-Ia and complement decreased subsequent Ia expression, suggesting that a proportion of Ia+ blasts were derived from Ia-bearing peripheral blood T cells. When the specificities of the Ia antigens on T-cell blasts were examined with alloantiserums, it was evident that the T blasts expressed similar HLA-DR determinants to those on B cells from the same donor; occasional minor differences between stimulated T cells and autologous B-cell lines or fresh B cells were encountered.

Cells, Cultured↗
PubMed1978

Glucocorticoids administered in vivo inhibit human suppressor T lymphocyte function and diminish B lymphocyte responsiveness in in vitro immunoglobulin synthesis.

The effects of corticosteroid given in vivo on human lymphocyte subpopulation function were investigated using an in vitro system of pokeweek mitogen-stimulated immunoglobulin production. Peripheral blood lymphocytes were obtained from normal volunteers before and 4 h after the intravenous administration of methylprednisolone. Unfractioned peripheral blood lymphocytes showed a consistent decrease (mean congruent with 50%) in immunoglobulin and total protein synthesis after steroid administration. Utilizing separated thymus-derived (T) and bone marrow-derived (B) lymphocyte fractions, the pathophysiology of this alteration in immunoglobulin production was elucidated. B lymphocytes obtained after steroid treatment showed a markedly diminished immunoglobulin response (20% of normal) to normal T lymphocytes and to normal T cells that had been irradiated to remove suppressor T lymphocyte function. All major classes of immunoglobulin (IgG, IgM, and IgA) were affected. T lymphocytes procured after steroid administration were capable of providing normal amounts of T cell help for B cells in immunoglobulin production. However, suppressor T lymphocyte activity, observed with normal T lymphocytes at high T to B cell ratios, was absent from the post-steroid T lymphocytes. This loss of suppressor T lymphocyte function was not due to the presence of excess help as irradiated pre- and poststeroid T cells provided equal amounts of helper activity. On recombining the poststeroid treatment B cells, which are hyporesponsive in immunoglobulin synthesis, with the posttreatment T lymphocytes, which lack suppressor activity, diminished amounts of immunoglobulin were produced which correlate well with the effects observed with unseparated cells. Thus, corticosteroids have differential effects on the lymphocyte populations involved in immunoglobulin biosynthesis. B cell responsiveness is diminished, suppressor T lymphocyte activity is removed, and helper T lymphocyte function is unaffected.

Adult↗
PubMed1978

Cellular collaboration in the production of human leucocyte migration inhibition factor.

The participation of cell subpopulations in the expression of leucocyte migration inhibition factor (LMIF) in response to Concanavalin A and Protein A was evaluated for cells isolated from the peripheral blood of five healthy subjects. LMIF activity could not be attributed to the function of T cells, B enriched cells, or monocytes acting alone, or to a combination of B enriched cells and monocytes. The LMIF response was the result of a collaborative event that occurred between T cells and B enriched cells, or between T cells and monocytes.

B-Lymphocytes↗
PubMed1978

Effect of corticosteroids on committed lymphocytes.

Human peripheral blood lymphocytes were cultured for 48 hr with concanavalin A. The amount of [3H]thymidine incorporated during the last 4 hr of culture, as well as the percentage of rosettes of activated lymphocytes generated, were assayed at the 48th hr. Adding 0.1 M alpha-methyl-D-mannoside (MAM) at progressively later times after the initiation of culture caused progressively less suppression because of the commitment phenomenon. This suppression was not exceeded by the addition of 10(-4) M preparations of corticosteroids and was statistically the same as that induced by a combination of both corticosteroids and MAM. The addition of PGE2 alone and in combination with methylprednisolone also failed to affect [3H]thymidine incorporation by committed lymphocytes.

Adrenal Cortex Hormones↗
PubMed1978

Effect of corticosteroids on the human immune response: comparison of one and three daily 1 gm intravenous pulses of methylprednisolone.

In spite of the increasing use of single and multiple pharmacologic intravenous pulses of MPS for immunosuppression in various diseases, their immunosuppressive effects have not been documented. We treated two groups of six patients with classic RA unresponsive to conventional therapy with either one or three daily 1 gm intravenous doses of MPS and measured the immune response and clinical activity over 16 weeks. Lymphocytopenia with selective T lymphocyte suppression was noted 2 hr following each infusion, which was maximal at 6 hr with complete recovery 24 hr after each dose beyond which no lymphocytopenia or T lymphocyte depletion was seen. Preservation of skin test positivity to recall antigens such as PPD and histoplasmin, rise in antibody titers to the secondary antigens tetanus and typhoid, and primary antibody response to KLH were found in both groups after treatment. Serum gamma globulin concentrations were unchanged. Five of six patients receiving 3 doses and three of six receiving 1 dose had satisfactory improvement in clinical parameters, with maximal benefit seen within the first 4 days. Six patients still felt better at 4 weeks, and one patient in each group entered a clinical remission greater than 16 weeks. We conclude that higher and repeated doses of MPS caused neither greater lymphocytopenia nor more prolonged suppression of recirculating lymphocytes than the conventional oral doses. The clinical benefits stem from reduction of inflammation, and it is doubtful that pulse therapy by itself induced significant generalized immunosuppression.

Aged↗
PubMed1977

Human lymphocytes subpopulations: rabbit red blood cell rosettes.

When human lymphocytes were incubated with rabbit red blood cells (RRBC) in vitro at 4 degrees C overnight, they adhered to form rosettes. 44 +/- 4.5% of thymocytes and o.7 +/- o.3% of peripheral blood lymphocytes (PBL) formed these rosettes. The rosette-forming cells (RFC) increased to 10--40% when the PBL were stimulated by mitogens. The increases were detected 4 h after culture and reached a maximum at 24 h, thus preceding significant increases in DNA syntheses. In another set of experiments, PBL were stimulated by a range of concentrations of each of 5 mitogens. The concentrations whick led to high DNA synthesis rates also generated high percentages of the rosettes. Lastly, PBL were activated by mitogens and the effect of inhibitors of DNA synthesis, protein synthesis and ATPase activity investigated. Only the latter could inhibit the generation of the RFC. In conclusion, 1y RRBC rosettes in mitogen stimulated human PBL were markers of activated lymphocytes, 2) the percentages of RFC could constitute a reliable index of mitogenic responses, and 3) this index was independent of the usual criteria of protein and DNA synthesis.

Adenosine Triphosphatases↗