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A N Warrens

Publications and source records attributed to A N Warrens.

29 records · Page 2Linked to original sources
PubMed1995

Definition of sites on HLA-DR1 involved in the T cell response to staphylococcal enterotoxins E and C2.

We have exploited the relative inefficiency of interaction between staphylococcal enterotoxins, SEE or SEC2, and H-2Ek compared to HLA-DR1 molecules to deduce which regions of the major histocompatibility complex (MHC) class II molecule are involved in the T cell response to these superantigens. Transfectants expressing hybrid DR/H-2E MHC class II molecules were used to present SEE to the T cell receptor V beta 8.1-expressing Jurkat cell line, and SEC2 to human peripheral blood T cells. For SEE, the critical region of the class II molecule for T cell reactivity and for binding was the beta 1 domain alpha-helix. The functional data were corroborated by measurements of direct binding. Sequence comparison between DR and H-2E raised the possibility that the glutamic acid at position 84 in the beta chain of H-2Ek, in place of glycine was responsible for the observed functional effects. This suggestion was supported by the finding that DQw2 (glutamine at 84) transfectants supported the SEE response much more efficiently than DQw6 that has glutamic acid at this position. In addition, amino acid substitutions at either position 36 or 39 in the DR alpha 1 domain abolished T cell reactivity without any obvious alteration in binding. For SEC2, use of transfectants expressing exon-shuffled alpha and beta chain genes showed that replacement of the alpha 1, alpha 2 and beta 1 domains with H-2E sequence inhibited the presentation of SEC2. Similarly, the substitutions at positions 36 and 39 in the alpha 1 domain abolished the T cell response to SEC2. Taken together, these data may be best explained by a model in which these two toxins have primary binding sites on the beta 1 domain (SEE) and the alpha 1 and alpha 2 domains (SEC2), but by virtue of a secondary binding site on the opposite surface of the class II molecule, cross-link two adjacent DR molecules. Such cross-linking may be important in the induction of T cell reactivity.

Amino Acid Sequence↗
PubMed1994

Transfected murine cells expressing HLA class II can be used to generate alloreactive human T cell clones.

Alloreactive human T cells are conventionally generated in vitro using peripheral blood mononuclear cells (PBMCs). The disadvantage of such an approach is that PBMCs express multiple HLA class II molecules and, as a consequence, it is difficult to generate T cells specific for an individual HLA alloantigen. This paper describes a technique in which T cell clones can be generated using stimulators which do express only one alloantigen. This has permitted the generation of HLA-DR-specific T cell clones and will be applied to produce T cell clones specific for other isotypes which cannot easily be obtained using other techniques. Murine DAP.3 cells were transfected with cDNAs encoding human class II molecules and used to stimulate primary alloresponses by purified human CD4+ T cells. The cloning of these T cells provided a good yield of cells allospecific for the class II molecule expressed by the transfected cells. A large percentage of the T cell clones were able to recognise human cells, suggesting that specificity for DR-bound peptides of mouse origin does not limit the applicability of this approach. Despite having been raised against mouse stimulators cells, the responses of the T cell clones to alloantigen-expressing human B cell lines were profoundly inhibited by anti-human LFA-3 monoclonal antibody. The possible mechanisms responsible for these results are discussed.

Animals↗
PubMed1994

Presentation and recognition of major and minor histocompatibility antigens.

The structural basis of allorecognition is heterogeneous. For minor histocompatibility antigen-specific T cells and for a minority of anti-MHC T cells (indirect allorecognition), the allogeneic molecule acts as any other protein, and is processed and presented as a peptide in the context of self MHC. In circumstances where the MHC molecule is recognized unprocessed on the surface of the allogeneic cell, we have postulated that the factors important in recognition are determined by the relationship between the responder and stimulator MHC molecules. When the alloresponse is directed against an allogeneic molecule whose exposed surface closely resembles that of the responder homologue, the alloresponse can be regarded as resulting from mimicry of self MHC-restricted recognition of peptides which are differentially bound by responder and stimulator MHC molecules. When the alloantigen differs extensively in the MHC restriction-determining region of the molecule from the equivalent product in the responder, a chance high-affinity cross-reaction with the foreign MHC structure itself may be the most important mechanism.

Amino Acid Sequence↗
PubMed1994

Myoblasts fail to stimulate T cells but induce tolerance.

Recent interest in myoblast transfer and in the use of myoblasts as vehicles in gene therapy has made it important to understand the potential immunogenicity of allogeneic or neoantigen-expressing myoblasts. Given the problems of producing a pure population of myoblasts, in this study we used a tumour-derived muscle cell line (TE671), with phenotypic features of myoblasts, which we transfected to express HLA-DR1. However, this cell line was unable to stimulate either established HLA-DR1-specific allorective T cell clones or a primary alloresponse. Nor could it present haemagglutinin peptide HA 306-324 to DR1-restricted, HA 306-324-specific T cell clones or lines. Indeed, preincubation with DR1-expressing TE671 and HA 306-324 rendered such T cells tolerant as judged by their subsequent inability to proliferate in response to a DR1+ B cell line plus peptide HA 306-324. These results imply that myoblasts do not provide costimulatory signals, and are therefore unlikely to stimulate allospecific T cells following myoblasts transplantation or to initiate neoantigen-specific immune responses following in vivo transfection.

Antigen-Presenting Cells↗
PubMed1991

Immunoreactive endothelin in human plasma, urine, milk, and saliva.

Using a highly sensitive radioimmunoassay, elevated plasma immunoreactive endothelin (ir-ET) levels were found in patients with diabetes mellitus (1.88 +/- 0.12 pmol/L, mean +/- SEM, n = 100), patients undergoing maintenance hemodialysis (4.28 +/- 0.76 pmol/L, n = 14), patients with acute myocardial infarction (3.43 +/- 1.03 pmol/L, n = 6), and patients with subarachnoid hemorrhage (4.92 +/- 0.64 pmol/L, n = 14) (normal controls: 0.54 +/- 0.05 pmol/L, n = 19). ir-ET was also present in urine (2.1 +/- 0.3 pmol/L, n = 12), breast milk (6.8 +/- 1.6 pmol/L, n = 16), and saliva (2.0 +/- 0.2 pmol/L, n = 15) obtained from healthy subjects. Chromatography studies verify the identity of endothelin. Fast protein liquid chromatography (FPLC) showed one peak in the normal plasma extract, three peaks in the plasma extracts from diabetic patients and patients undergoing maintenance hemodialysis, three peaks in the urine extract, four peaks in the milk extract, and five peaks in the saliva extract. When the materials eluting in the void volume on FPLC of urine and saliva extracts were loaded onto a Sephadex G-25 column, the ir-ET was eluted in a higher molecular weight region. Incubation of endothelin-1, endothelin-2, and endothelin-3 in urine for 5 h showed that the total amount of ir-ET decreased to less than 30% of the initial levels, suggesting that endothelins are very unstable in urine.

Adult↗
PubMed1990

Endothelin in renal failure.

Endothelin is a 21-residue peptide vasoconstrictor produced by endothelium. Using a radioimmunoassay, endothelin values were measured in four groups of individuals: normal controls (0.54 +/- 0.12 pmol/l, n = 20); undialysed patients with chronic renal failure (CRF) (0.82 +/- 0.13 pmol/l, n = 38); chronic renal failure patients on continuous ambulatory peritoneal dialysis (CAPD) (2.81 +/- 0.63 pmol/l, n = 20); and patients with CRF on haemodialysis (HD) (4.52 +/- 1.21 pmol/l, n = 14). The endothelin values were significantly greater in undialysed patients with CRF when compared with controls (P less than 0.001) and significantly greater in both dialysis groups when compared with controls and the undialysed CRF group (P much less than 0.001). The difference between the two dialysis groups was not significant (P = 0.07). There was no correlation between endothelin and serum creatinine, mean arterial pressure, presence of chronic hypertension and/or diabetes, use of calcium-channel blockers and/or ACE inhibitors, or primary renal diagnostic category. A single haemodialysis session had no significant effect on endothelin values in the ten patients in whom this was assessed. Fast protein liquid chromatography (FPLC) appeared to confirm that the molecular species found in chronic renal failure were the same as those found in diabetic patients.

Adolescent↗
PubMed1990

Positive diagnosis of self-medication with homatropine eye drops.

A 25-year-old man with a variety of unusual ocular symptoms was fully investigated and no abnormality discovered. The suspicion of self-medication with a mydriatic was confirmed when homatropine was isolated in his tears. We describe a method for collecting tears which allowed biochemical confirmation at leisure.

Adult↗
PubMed1987

Thoracic outlet compression syndrome: the lack of reliability of its clinical assessment.

Four manoeuvres advocated for the assessment of thoracic outlet compression were performed on 64 randomly chosen volunteers. Although only 17% had any symptoms of thoracic outlet compression, 58% had a positive result in at least one of the manoeuvres. Only 2% were positive for more than two manoeuvres. We suggest this low specificity devalues these tests in clinical practice. We were unable to correlate our clinical results with the findings of digital photoplethysmography.

Adolescent↗