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M McMillan

Publications and source records attributed to M McMillan.

At least 19 recordsLinked to original sources
PubMed1996

Sclerosing peritonitis occurring in a hemodialysis patient.

The pathogenesis of sclerosing peritonitis is poorly understood. In patients with end-stage renal failure, it has been described in association with continuous ambulatory peritoneal dialysis (CAPD), although it has not been described in patients treated exclusively by hemodialysis. We present a case of sclerosing peritonitis occurring in a 47-year-old man who was treated solely by hemodialysis. Additionally, the patient was diagnosed as having "nephrogenic ascites" 5 years before developing sclerosing peritonitis, and we discuss a possible link between these two conditions.

Ascites↗
PubMed1995

Patterns of cytokine secretion by autoreactive proteolipid protein-specific T cell clones during the course of multiple sclerosis.

To determine whether cytokine secretion patterns change with disease status in patients with multiple sclerosis (MS), we measured IFN-gamma, TNF-alpha beta, IL-4, IL-6, IL-10 and TGF-beta secretion in a panel of T cell clones (TCCs) specific for proteolipid protein (PLP) after stimulation with PLP peptides or polyclonal activators. During acute attack, the predominant pattern of cytokine secretion resembled that of murine Th1 cells; i.e, IFN-gamma and TNF-alpha beta, and appeared to be restricted to PLP-reactive TCCs. None of the TCCs isolated during acute attack produced TGF-beta in response to PLP, Con A, or anti-CD3 Ab. Half of these TCCs were, however, capable of TGF-beta secretion and mRNA expression upon stimulation with PMA and the calcium inonphore A23187, suggesting a possible defect in activation through the TCR/CD3 pathway. During remission in the same patients all but two PLP-TCCs showed patterns of cytokine secretion resembling that of murine Th0, Th1, and Th2 subsets. The levels of IL-10 secreted by these TCCs were significantly higher than those of TCCs isolated during acute attacks and those derived from normal subjects and patients with other noninflammatory neurologic diseases. Furthermore, 50% of these TCCs were capable of producing TGF-beta after Ag-specific or polyclonal stimulation. All TCCs isolated from control subjects exhibited a Th0 like secretion profile. These data indicate that different stages of disease in MS are characterized by different patterns of cytokine secretion by PLP-specific TCCs, suggesting a role for cytokines in clinical events during the course of MS.

Autoantigens↗
PubMed1995

Dissection of cross-reactivities using a panel of H-2Ld alloreactive T cell hybridomas.

In order to explore the role which class I structure plays in alloreactivity, we have generated Ld-reactive T cell hybridomas by fusion of a dm2 anti-BALB/cJ MLR with the BW5147 cell line and examined their stimulation by the following class I molecules (alpha 1/alpha 2/alpha 3): Lq, Dq, dm1, Ld/Ld/Dd, Lq/Dq/Ld, and Q10/Q10/Ld. We found that their specificities differed in their patterns of cross-reactions and were reasonably representative of those present in the bulk population of MLR-generated CTLs. Ld/Ld/Dd and Q10/Q10/Ld stimulated the majority of the hybridomas, Lq and dm1 were recognized by over half of the panel, and Lq/Dq/Ld stimulated only modestly, while Dq was not recognized by any hybridoma. Correlation of these observed reactivities with class I structure suggests that putative TCR contact residues may play a significant role in recognition when compared to the polymorphic amino acid residues which control pocket specificity and peptide binding. Specifically, Lq and Dq possess very similar or identical pockets, in contrast to those of dm1 and Q10. However, Q10 has identical TCR contact residues to Ld, both on the alpha 1 and alpha 2 alpha helices, unlike Dq which is mismatched on both helices. Lq and dm1 are mismatched compared to Ld on only one helix. Thus, a molecular rationale for the cross-reactions observed in this study involves the direct participation of residues of class I molecules in allorecognition.

Amino Acid Sequence↗
PubMed1995

Myelin proteolipid protein-induced Th1 and Th2 clones express TCR with similar fine specificity for peptide and CDR3 homology despite diverse V beta usage.

Myelin-specific T-helper (Th) cells which induce encephalomyelitis belong to the inflammatory Th1 subset. Th2 cells recognizing similar epitopes potentially represent specific inhibitors of encephalitogenic Th1 cells. Since the differential stimulation of antigen-specific Th2 cells may be important in the regulation of autoimmune inflammatory disorders, we have examined the fine specificity of a Th1 and a Th2 clone, induced by immunization of SJL mice with native proteolipid protein (PLP) and specific for the PLP 139-151 sequence. Stimulation of the clones by synthetic peptides containing single alanine substitutions demonstrated that L141, W144, H147, and P148 represent critical residues. Surprisingly, this pattern was identical for both subsets. Competition studies indicated indirectly that L141 and P148 may be MHC-binding residues, whereas W144 and H147 contact the TCR. Sequencing of the TCR expressed by both Th subset clones demonstrated different V beta usage as well as variation in the D-region sequence and length. Interestingly, realignment of the sequence of the CDR3 regions showed striking homology. This study demonstrates that Th1 and Th2 subsets can express very similar peptide specificities, while utilizing very different TCR V beta chains. These results suggest that the therapeutic modalities based on either peptide antagonists or antibodies specific for CDR3 may have limited effectiveness in treating autoimmune disorders, since they may also target the beneficial arm of the immune response.

Amino Acid Sequence↗
PubMed1995

Isolation and characterization of autoreactive proteolipid protein-peptide specific T-cell clones from multiple sclerosis patients.

During the course of multiple sclerosis (MS), myelin proteins are likely antigenic targets for autoreactive T cells. Although most studies have implicated myelin basic protein as a potent encephalitogenic myelin component, proteolipid protein (PLP) appears also to be a possible target antigen in the autoimmune response in MS. In this report, we investigated the human T-cell responses to PLP by using PLP104-117 and PLP142-153 synthetic peptides as target antigens in limiting dilution. One hundred twenty-five CD4+, T-cell receptor (TCR) alpha beta+ T-cell clones (TCCs) were established from the peripheral blood of seven MS patients and five control subjects. Despite the use of enriched cultures no gamma delta TCCs were obtained. Recognition of both PLP epitopes occurred in the context of multiple HLA-DR alleles. We found no differences in restriction element usage between MS patients and control subjects. TCR variable beta-region (V beta) usage was assessed by flow cytometry using a panel of monoclonal antibodies defining different V beta elements. In both MS patients and control subjects, there was a marked heterogeneity in the TCR V beta repertoire. Furthermore, sequential evaluation of MS patients during acute attacks and clinical remissions showed even more broadening of the TCR V beta repertoire. These data demonstrate that a heterogeneous T-cell response to PLP concerning HLA restriction and TCR usage is present in both MS patients and normal subjects.

Adult↗
PubMed1994

Limited T cell response to donor MHC peptides during allograft rejection. Implications for selective immune therapy in transplantation.

Previously, we have demonstrated that during allograft rejection, MHC molecules of the donor are processed and presented to alloreactive CD4+ T lymphocytes in the form of peptides associated with the MHC class II molecules of the recipient. There is an increasing body of evidence that this indirect pathway of allorecognition may play a major role in allograft rejection. Herein, we have used a series of overlapping MHC peptides progressing along the sequence of the donor MHC molecule in single residue steps. We have mapped all potential MHC Ag determinants to which T cell responses could be generated after s.c. injection of allogeneic splenocytes. We have shown that splenic T cell proliferative responses to the beta 1 domains of donor Ak, Ad, and A(s) mouse MHC class II molecules were directed toward a single immunodominant determinant in each of three donor/recipient combinations. Interestingly, after allogeneic spleen cell transplantation, an additional determinant on donor MHC could be detected in the draining lymph nodes. This result shows that the fine specificity of T cell response to donor transplantation Ags can differ between lymphoid organs. Then, we investigated whether limitation of T cell response to donor MHC peptides applies to the clinical situation of a graft. We have shown that after an allogeneic skin graft, self-restricted alloreactive T cells proliferated to the same determinant on the donor MHC molecule. These results indicate that immune intervention, such as tolerance induction to the dominant T cell determinant on donor MHC molecules, may be developed for the prevention of allograft rejection.

Amino Acid Sequence↗
PubMed1994

Mutations inside but not outside the peptide binding cleft of the H-2 Ld molecule affect CTL recognition and binding of the nucleoprotein peptide from the lymphocytic choriomeningitis virus.

In order to investigate the role of residues inside and outside the peptide binding cleft of the Ld molecule in peptide presentation to cytotoxic T lymphocytes (CTL), we constructed a series of point mutations in the Ld gene. We determined the effects of the mutations in the Ld molecule on the binding and recognition of an Ld-restricted CTL epitope derived from the nucleoprotein (NP) of the lymphocytic choriomeningitis virus (LCMV). Each of the mutations within the Ld peptide binding cleft resulted in a complete loss of CTL recognition. Addition of the LCMV NP peptide to cells expressing these mutants did not increase surface Ld expression, suggesting that the mutations altered peptide binding. Mutations involving pockets D and E within the cleft affected LCMV peptide binding and recognition as drastically as those in pocket B, which was predicted to interact with a main anchor residue of the peptide. In striking contrast, the mutations located outside the cleft did not change either recognition or binding. These results demonstrate that the Ld residues in the peptide binding cleft are the main determinants dictating LCMV NP peptide binding, and that the residues in each of the pockets within the cleft play a role in this interaction. Surprisingly, one mutation outside the peptide binding cleft, T92S, abrogated CTL lysis of target cells treated with the LCMV NP peptide, but not virus-infected cells. These data show that this mutation selectively altered the presentation of the LCMV NP peptide introduced to the cell exogenously, but not endogenously. This implies that the pathway by which peptides associate with class I molecules within the cell differs from that of exogenous peptide binding.

Amino Acid Sequence↗
PubMed1994

Effects of alloimmune injury on contraction and relaxation in cultured myocytes and intact cardiac allografts.

OBJECTIVES: This study was performed to determine the mechanisms by which allosensitized lymphocytes cause contractile dysfunction in cultured ventricular myocytes and to compare the effects on isolated myocytes with those observed in an intact heart preparation during allograft rejection. BACKGROUND: Allograft rejection may be associated with reversible abnormalities of both systolic and diastolic function. The immunologic mechanisms that cause ventricular dysfunction are poorly understood. METHODS: Vascularized heterotopic abdominal heart transplantation was performed in mice. Contractile function of excised allografts undergoing rejection was assessed using a Langendorff perfusion apparatus and a strain gauge. Spontaneously beating monolayers of cultured ventricular myocytes from donor strain fetal mice were exposed to the allosensitized cytotoxic T lymphocytes, and the effects on myocyte motion, intracellular calcium transients, relaxation half-time, membrane potential and myocyte lysis (chromium-51 release) were measured. RESULTS: In intact hearts, histologically mild rejection without myocyte necrosis was associated with decreased systolic function without slowing of relaxation. In cultured fetal myocytes, sensitized lymphocytes induced a progressive decrease in the amplitudes of myocyte motion and calcium transients, with cessation of beating within 40 min. Also, the diastolic membrane potential and amplitude of the action potential decreased. Relaxation half-time, as estimated by measurement of cell motion, was unchanged. The effect was allospecific and was reversible with early removal of lymphocytes from the myocyte monolayer. Pretreatment of lymphocytes with the degranulation inhibitor 4,4'-diisothiocyano-2,2'-disulfonic acid stilbene blocked both the negative inotropic effect and myocyte lysis. CONCLUSIONS: We conclude that impaired relaxation is not a prominent feature of contractile dysfunction caused directly in myocytes by alloimmune injury from cytotoxic lymphocytes. Allosensitized lymphocytes can cause reversible systolic dysfunction in myocytes by means of a direct cell-cell interaction. This effect may be in part responsible for the reversible systolic dysfunction associated with allograft rejection.

Animals↗
PubMed1994

Disruption of the determinant hierarchy on a self-MHC peptide: concomitant tolerance induction to the dominant determinant and priming to the cryptic self-determinant.

The presentation of self-peptides in a self-restricted manner plays a critical role in the complex positive and negative selective process of T cell recognition of self-determinants. The population of determinants comprises (i) a dominant set which is efficiently presented and induces clonal elimination or inactivation of the corresponding autoreactive T cells, and (ii) a cryptic set which is not processed efficiently enough to reach the threshold of presentation to make an impact on the T cell repertoire during thymic selection. Here we have studied a self-MHC peptide, Ld 61-85, which as shown in earlier work was able to induce vigorous T cell proliferation in syngeneic animals. Despite the fact that this peptide as a whole is 'cryptic', the fine specificity of the class II restricted response was complex, in that there were three distinct and overlapping T cell determinants: the dominant determinant, Ld 65-80, flanked by two cryptic determinants, Ld 61-75 and Ld 73-85, all of which compete for stimulating in vivo autoreactive T cell proliferative responses. The hierarchy of these determinants bears an interesting relationship to tolerance. Ld 61-85 or Ld 61-80 priming induces proliferation only to Ld 65-80; likewise, tolerance induction to Ld 61-80 prevents elicitation of a subsequent response to Ld 61-80 or Ld 65-80 in the local lymph nodes. However, in the Ld 61-80 tolerant mice, in vivo challenge with Ld 61-80 induces a strong T cell proliferative response directed towards cryptic Ld 61-75.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗
PubMed1994

Phosphatidyl inositol-linked forms of a murine class I MHC molecule expressed on Chinese hamster ovary cells retain peptide binding capability and alloreactivity.

A gene encoding a phosphatidyl inositol-linked form of the murine class I MHC molecule H-2Kd was constructed and the protein expressed in Chinese hamster ovary cells together with murine or human beta 2-microglobulin (beta 2m). The resulting lipid-linked class I heterodimers can be efficiently converted into a soluble form by treatment of transfected cells with a phospholipase. Cells expressing Kd heterodimers were characterized with respect to heavy chain levels at the cell surface, peptide binding, and recognition by Kd-specific antibodies and alloreactive cytotoxic T cells. All transfectants bound a 3H-labeled Kd-restricted nonamer peptide, although more peptide bound to cells expressing the Kd/human beta 2m combination, perhaps because of a greater number of empty molecules at the cell surface. A dissociation constant of 5 x 10(-8) M derived by Scatchard analysis is within the range expected for interactions of peptides with class I MHC molecules. Alloreactive cytotoxic T cells which recognize wild-type Kd on murine cells lysed the hamster cells expressing lipid-linked Kd without regard to the species of the beta 2m light chain. These results indicated that the engineered lipid-linked Kd molecule is expressed at the cell surface, is recognized by antibodies and T cells, and functions to bind peptide.

Amino Acid Sequence↗
PubMed1993

An endogenously synthesized decamer peptide efficiently primes cytotoxic T cells specific for the HIV-1 envelope glycoprotein.

The immunodominant H-2Dd-restricted cytotoxic T lymphocyte (CTL) response to the HIV-1 gp160 envelope glycoprotein maps to a single determinant in the V3 loop, designated p18. Using a series of peptides synthesized on pins we have determined that the minimal core sequence of this determinant required for CTL recognition comprises 8 amino acids (residues 320-327). However, 9mer and 10mer peptides containing this core sequence were more effective than the 8mer peptide at sensitizing Dd-expressing target cells. To analyze the antigenicity of endogenously synthesized p18, minigenes encoding a 10-amino acid determinant (residues 318-327) and a 67-amino acid peptide (residues 281-348; containing the V3 loop) were expressed using vaccinia virus (Vac) recombinants. Both peptides were as effective as wild-type gp160 in their ability to sensitize target cells for lysis by gp160-specific CTL. Immunization of BALB/c mice with Vac recombinants encoding both gp160 peptides elicited gp160-specific CTL. These data demonstrate that both the V3 loop itself and a 10-residue epitope are sufficient to prime CTL in vivo and strongly support the potential use of minigene-encoded CTL epitopes for recombinant vaccines designed to induce protective T cell-mediated immunity against HIV-1.

AIDS Vaccines↗
PubMed1993

Characterization of the Ld-restricted cytotoxic T-lymphocyte epitope in the mouse hepatitis virus nucleocapsid protein.

The mouse hepatitis virus (MHV) JHM strain (JHMV) produces primary demyelination in the central nervous system associated with acute encephalomyelitis. Humoral and cellular immune responses both participate in controlling the development of chronic MHV-induced demyelination. A subset of the CD8+ cytotoxic T lymphocytes (CTL) induced by immunization of BALB/c (H-2d) mice with JHMV is specific for the viral nucleocapsid protein. This CTL population recognizes an epitope located within the carboxy-terminal 149 amino acids in association with the Ld class I molecule (S. A. Stohlman, S. Kyuwa, M. Cohen, C. Bergmann, J. P. Polo, J. Yeh, R. Anthony, and J. G. Keck, Virology 189:217-224, 1992). Using a panel of vaccinia virus recombinants expressing truncated forms of the nucleocapsid protein and a series of overlapping synthetic peptides, we mapped the response to 15 amino acids. This sequence, encompassing the MHV epitope, contains the Ld-specific binding motif. The predicted 9-mer peptide (residues 318 to 326: APTAGAFFF) was sufficient and highly active in sensitizing target cells for CTL recognition when either added exogenously or synthesized intracellularly. Cross-reactivity of JHMV nucleocapsid protein-specific CTL with six other MHV strains indicated that natural sequence variations within the 9-mer epitope are tolerated in positions 4 and 5, whereas all other amino acids are conserved. These data define a novel 9-mer Ld-restricted CTL epitope which represents the first MHV CTL epitope. Characterization of this epitope provides a molecular basis to study the role of nucleocapsid protein-specific CTL in the clearance of JHMV from the central nervous system.

Amino Acid Sequence↗
PubMed1993

ATP depletion causes a reversible decrease in Na+ pump density in cultured ventricular myocytes.

To examine factors contributing to impaired K+ homeostasis induced by prolonged but sublethal ATP depletion, we subjected cultured chick ventricular myocytes to metabolic inhibition with 20 mM 2-deoxy-D-glucose plus 1 mM NaCN for 2 h and then allowed myocytes to recover for 5 days in medium containing 6% fetal calf serum (FCS) or in hormone-supplemented serum-free medium. We measured spontaneous contractions (with a video motion detector), K+ content, K+ uptake, membrane potential, and Na+ pump density ([3H]ouabain binding). Exposure to metabolic inhibition for 2 h caused an acute decrease in Na+ pump site density [8.2 +/- 1.1 to 3.8 +/- 0.8 (SE) pmol/mg protein; n = 9, P < 0.02]. Compared with control cells (no metabolic inhibition, cultured for 5 days in serum-free medium), Na+ pump density remained depressed in cells recovered from metabolic inhibition in serum-free medium (3.0 +/- 0.7 pmol/mg), and this was associated with persistently depressed K+ uptake (54% of control), K+ content (67% of control), and membrane depolarization (-19 +/- 2 mV), a significant decrease in cell number (79% of control), and failure to resume spontaneous contractions. Exposure of cells inhibited for 2 h to culture medium containing 6% FCS resulted in a return of Na+ pump site density toward normal levels by 5 days, associated with recovery of K+ uptake and K+ content, preservation of cell number, and resumption of contraction.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenosine Triphosphate↗
PubMed1992

Donor major histocompatibility complex (MHC) peptides are presented by recipient MHC molecules during graft rejection.

Peptides from donor major histocompatibility complex (MHC) molecules were examined for their activation of allogeneically primed T cells. After immunization with either allogeneic spleen cells or a skin allograft, primed T cells proliferate in response to peptides derived from polymorphic regions of alpha and beta chains of class II allo-MHC molecules. The results demonstrate that presentation of donor-MHC peptides by host-derived antigen-presenting cells is a common event in vivo. Thus, self-restricted T cell recognition of processed alloantigens may play a critical role in transplantation. An in-depth understanding of this response may result in the development of additional molecular therapies to combat allograft rejection.

Animals↗
PubMed1991

Dissection of binding vs. recognition functions of H-2 class-I synthetic peptides which are recognized by alloreactive cytotoxic T lymphocytes.

Cytotoxic T lymphocytes (CTLs) cause specific destruction of allografts and viral-infected cells. While viral-restricted CTLs recognize viral peptides in association with class-I molecules encoded in the major histocompatibility complex, the role which peptides play during allorecognition remains obscure. We have shown previously that Ld-specific alloreactive CTLs can recognize the peptide Ld61-80 (or Ld61-85) in association with the dmI class-I molecule. We have now developed an assay, based on inhibition of cytotoxicity, in which we can monitor peptide binding to the dmI molecule in the absence of CTL recognition. In this report we have used this assay to differentiate those amino acids of the peptide Ld61-80 which contribute to class-I binding from those involved with T-cell-receptor (TCR) interactions.

Amino Acid Sequence↗
PubMed1991

Assessing comprehensive nursing performance: the Objective Structural Clinical Assessment (OSCA). Part 1--Development of the assessment strategy.

Nursing courses in Australia are preparing graduates for comprehensive practice within Universities. The evaluation of safe and effective comprehensive nursing performance requires the consideration of a much broader range of practice competencies than has previously been the case. In particular there is a need to explore integrated assessment approaches that closely resemble the realities of the health care setting. Part 1 of this paper provides an overview of the Objective Structured Clinical Assessment (OSCA) which it is suggested is an effective way of assessing student comprehensive nursing performance. Some theoretical considerations in OSCA development are discussed and then an outline of the processes involved in designing and implementing an OSCA provided. Part 2 describes an evaluation project supported by the NSW Nurses' Registration Board. The aim of the study was to determine the validity and reliability of the use of the OSCA as an integrated assessment tool as a measurement of the extent to which a student nurse can plan and deliver safe and effective comprehensive nursing care.

Australia↗
PubMed1991

Assessing comprehensive nursing performance: the objective structured clinical assessment (OSCA). Part 2--Report of the evaluation project.

Part 1 of this paper described the development of an assessment strategy used to measure the clinical performance of student nurses undertaking preparation for practice within the tertiary education sector. The challenge of developing an appropriate technique in assessment to accommodate a comprehensive nursing register was described. Features of the design and implementation were also provided. Part 2 describes an evaluation project developed by the staff and supported by a research grant from the New South Wales (NSW) Nurses Registration Board. The aim of the study was to determine the validity and reliability of the Objective Structured Clinical Assessment (OSCA) technique. The research design incorporated the use of triangulated data: student questionnaires, judgments made by a panel of experts and an analysis of the statistical correlation between the students' results in the OSCA and results in other areas of assessment.

Clinical Competence↗