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Biomedical subjects

R G Miller

Publications and source records attributed to R G Miller.

At least 19 recordsLinked to original sources
PubMed1992

Effect of class I MHC binding peptides on recognition by natural killer cells.

NK cells can recognize and destroy a broad range of cells, including many tumor cells and virally infected cells, yet spare most normal cells. Identification of the target structure recognized by these cells has proved elusive. An attractive hypothesis is that, unlike B cells and T cells that recognize a specific foreign marker, NK cells respond to the absence of a "self" marker. Class I MHC molecules have been implicated as the self markers whose absence can trigger lysis. We show here that normal cells are lysed on incubation with IL-2-activated NK cells if peptides that can bind to the class I MHC molecules of the normal cells are also included in the assay, and speculate that this binding is somehow removing a self marker that normally protects a cell from lysis. NK cells were derived from splenocytes of young (5 to 8 wk old) athymic nude BALB/c (H-2d) or nude C57Bl/6 (H-2b) mice incubated with 1000 U/ml rIL-2, and target cells were derived from splenocytes of normal BALB/c or C57Bl/6 mice incubated with Con A. Peptides were from xenogeneic, viral, self, and mutated self protein sequences and included sequences specific for Kd, Kb, Db, and Ld. All peptides increased lysability of those targets to which they could bind.

Amino Acid Sequence↗
PubMed1992

Correlation between lymphocyte-induced donor-specific tolerance and donor cell recirculation.

Intravenous infusion of mice with major histocompatibility complex (MHC) incompatible lymphocytes can inhibit the response of recipient T cells capable of recognizing the injected cells, and can enhance survival of grafts sharing MHC with the injected cells. However, neither T cell inactivation nor graft survival enhancement is always achieved. This is particularly true for donor cells that are fully allogeneic (as compared to semiallogeneic) to the recipient. We show here that both donor-specific induced response reduction and graft survival enhancement are directly correlated with the ability of the injected lymphoid cells to persist in the recirculating lymphocyte pool of the host. Whether donor cells persist correlates inversely with the level of natural killer cell (NK) activity in the host. Fully allogeneic cells can only persist in hosts with low NK activity and can then induce response reduction. Both persistence and response reduction are abrogated by injection of the host with poly-I:C, a treatment that boosts host NK activity. The same treatment also destroys the ability of semiallogeneic injected cells to persist, to induce response reduction, and to enhance skin graft survival.

Animals↗
PubMed1992

Peripheral deletion of mature CD8+ antigen-specific T cells after in vivo exposure to male antigen.

It has been well established that T cell tolerance to self Ag occurs primarily via clonal deletion of immature thymocytes in the thymus. Evidence also exists that there are additional mechanisms operative on mature T cells for establishing and maintaining tolerance in the periphery. To follow the fate of mature Ag-specific T cells in vivo, we used female transgenic mice, which contain a large population of male H-Y Ag-specific T cells that can be identified by immunostaining with mAb directed against CD8 and the transgenic TCR. H-Y Ag was introduced into these mice by injecting Ag-bearing male lymphocytes using conditions known to induce CTL precursor response reduction. The number of Ag-reactive CD8+ transgenic T cells in the periphery started to decrease after 2 days of in vivo exposure to male Ag. Decline was maximum (up to 80% of total) by 7 days, and stayed at this level for at least 6 wk. CD4+ cells and those CD8+ cells that did not carry the transgenic TCR were not affected. Most or all of the remaining Ag-reactive CD8+ cells in the periphery were fully responsive when stimulated by male Ag in vitro. Maturation of transgenic T cells in the thymus of injected mice remained the same as that of control animals. Our data provide direct evidence that mature Ag-reactive CD8+ cells are susceptible to clonal deletion in the periphery when exposed to the Ag in vivo. These findings suggest the presence of two types of APC in the periphery: stimulatory APC (e.g., macrophages and dendritic cells) required for initiating an active immune response; and functionally deleting APC (or veto cells) capable of deleting mature T lymphocytes that recognize Ag presented on their surface. Functionally deleting APC that present self Ag to peripheral T cells may provide a fail-safe mechanism against autoreactive cells that escaped deletion during differentiation in the thymus.

Animals↗
PubMed1992

Normal dystrophin transcripts detected in Duchenne muscular dystrophy patients after myoblast transplantation.

Gene delivery by transplantation of normal myoblasts has been proposed as a treatment of the primary defect, lack of the muscle protein dystrophin, that causes Duchenne muscular dystrophy (DMD), a lethal human muscle degenerative disorder. To test this possibility, we transplanted normal myoblasts from a father or an unaffected sibling into the muscle of eight boys with DMD, and assessed their production of dystrophin. Three patients with deletions in the dystrophin gene expressed normal dystrophin transcripts in muscle biopsy specimens taken from the transplant site one month after myoblast injection. Using the polymerase chain reaction we established that the dystrophin in these biopsies derived from donor myoblast DNA. These results show that transplanted myoblasts persist and produce dystrophin in muscle fibres of DMD patients.

Adult↗
PubMed1992

Hybrid resistance in vitro. Possible role of both class I MHC and self peptides in determining the level of target cell sensitivity.

NK cells of F1 hybrids frequently exhibit an enhanced capacity to reject semisyngeneic parental bone marrow grafts, a phenomenon known as hybrid resistance. Attempts to define the mechanism whereby this occurs have been hampered by factors inherent in the use of an in vivo model, including the host immune response, microenvironment, immune cell trafficking patterns, and host irradiation. We show here that IL-2-activated NK cells (lymphokine-activated killer cells) can be used to establish an in vitro model that appears to mimic hybrid resistance. These effectors lyse parental lymphoblast targets in a pattern consistent with that observed in vivo, bear NK not T cell surface markers, and recognize target structures mapping to the MHC. By using this model, we then demonstrate that sensitivity to lysis of syngeneic F1 lymphoblasts can be augmented by exposing the targets to conditions that have been reported to permit the exchange of endogenous class I-bound self peptides for exogenous foreign sequences. These data suggest that both MHC class I molecules and the "self" peptides they bind contribute to determining the susceptibility of a target to hybrid resistance, and the data are discussed in the context of a model of NK recognition in which the sensitivity of a target to NK lysis is mediated by a complex of the class I MHC molecule and the self peptides it samples from the intracellular peptide pool.

Animals↗
PubMed1992

Role of plasmapheresis in acute disseminated (postinfectious) encephalomyelitis.

Acute disseminated encephalomyelitis (ADEM) is a demyelinating central nervous system disease that is associated with high morbidity and mortality. Although the recognition of ADEM may be facilitated by newer imaging techniques, the optimal treatment of this disease remains uncertain. We describe 4 patients with severe ADEM who responded to treatment that included intensive plasmapheresis. Two of the patients were in coma at the time that plasmapheresis was instituted, and all 4 patients made an excellent recovery. Immunologic studies revealed increased serum IgA levels, increased circulating immune complex levels as measured by the Raji cell assay, and decreased numbers of T and B cells prior to treatment of ADEM. These abnormalities improved following plasma exchange. Plasmapheresis appears to be effective in reversing the neuropathologic process in ADEM. The role of this treatment modality in ADEM requires further evaluation in controlled clinical trials.

Acute Disease↗
PubMed1992

Case-of-the-month: autosomal recessive myotonia congenita: marked muscle weakness in a 16-year-old boy.

A 16-year-old boy had a 10-year history of stiffness in leg muscles. There was marked weakness of neck flexors, shoulder abductors, and ankle dorsiflexors, with hypertrophy of most muscle groups and both action and percussion myotonia. The parents were normal. Motor unit potential mean duration was reduced in the weakest muscle (tibialis anterior), and a biopsy of the same muscle showed only minimal abnormalities. Exercise and repetitive stimulation (30 Hz) of the tibialis anterior disclosed a decline in the compound muscle action potential that appeared to correlate with the muscular weakness.

Adolescent↗
PubMed1992

Dantrolene sodium and fatigue of long duration.

A long-lasting impairment of muscular force generation follows fatiguing exercise (fatigue of long duration), the physiological basis of which is not well understood. To investigate the role of reduced calcium release in long-lasting fatigue, we examined the effects of dantrolene sodium, which selectively decreases calcium release from the sarcoplasmic reticulum. The drug impaired muscle function in a pattern identical to that of long-lasting fatigue. The results are consistent with either independent effects of dantrolene and exercise at the same site in the excitation-contraction coupling chain, or independent actions at separate serial sites.

Adult↗
PubMed1992

Characterization of alpha beta+ CD4- CD8- CTL lines isolated from mixed lymphocyte cultures of adult mouse spleen cells.

Several CD4- CD8- and CD4- CD8+ T cell lines and clones have been isolated from the same mixed lymphocyte cultures. They express the alpha beta T cell receptor, are CD3+, V beta 8- and heat stable antigen-, and exhibit highly specific cytolytic activity mapping to H2Db. However, monoclonal antibody against H2Db failed to block lysis by CD4- CD8- cytotoxic T lymphocytes (CTL). One possible explanation is that the "double negative" cytotoxic T lymphocytes may recognize H2Db in the context of other class I molecules (Qa/Tla). CD4 and CD8 could be detected on some lines cloned in high concentrations of EL4 supernatant and the cell surface expression was influenced by growth conditions. The alpha beta+ CD4- CD8- CTL described in this report are clearly different from the so-called "autoimmune double negatives" which suggests a function for them in normal immune responses.

Animals↗
PubMed1992

Surgical trauma, Candida infection, and serum proteolytic activity.

Both surgical trauma and infection can disturb the proteinase to proteinase inhibitor balance in the circulation. We sought to assess the effect of Candida albicans infection (INFX) on postoperative mortality, to correlate mortality with total serum proteolytic activity (PA), and to assess the impact of exogenous proteinase inhibitors (PI) on this mortality. Mice underwent midline laparotomy (LAP) and immediate postoperative intravenous C. albicans infection. LAP + INFX shortened mean survival compared to INFX or LAP alone. Quantitative renal cultures confirmed that death in the LAP + INFX and INFX groups was due to Candida sepsis. PA was measured using an 125I-labeled protein assay, yielding micrograms of acid-soluble peptides/100 microliters of serum. In control, sham-operated, and LAP groups, PA averaged less than 9.0, and mortality was 0. In INFX and LAP + INFX groups, PA averaged greater than 14.5 and mortality was high. To determine if high PA was related to high mortality, LAP + INFX mice were treated immediately preoperatively with a single dose of PI (1 mg alpha 1-proteinase inhibitor, 1 mg antithrombin, and 1000 KIU aprotinin). Mean survival increased with PI treatment. In conclusion, the addition of Candida infection to surgical trauma hastened mean time to death. More rapid death correlated with elevated PA and may reflect systemic imbalance in the proteinase to proteinase inhibitor ratio in the circulation. PI improved survival, suggesting that proteinase inhibition may prove useful in the future in the treatment of fungal sepsis in surgical patients.

Animals↗
PubMed1992

Peripheral tolerance through clonal deletion of mature CD4-CD8+ T cells.

Transgenic mice bearing the alpha beta transgenes encoding a defined T cell receptor specific for the male (H-Y) antigen presented by the H-2Db class I MHC molecule were used to study mechanisms of peripheral tolerance. Female transgenic mice produce large numbers of functionally homogeneous CD8+ male antigen-reactive T cells in the thymus that subsequently accumulate in the peripheral lymphoid organs. We have used three experimental approaches to show that male reactive CD8+ T cells can be eliminated from peripheral lymphoid organs after exposure to male antigen. (i) In female transgenic mice that were neonatally tolerized with male spleen cells, male reactive CD8+ T cells continued to be produced in large numbers in the thymus but were virtually absent in the lymph nodes. (ii) Injection of thymocytes from female transgenic mice into female mice neonatally tolerized with the male antigen, or into normal male mice, led to the specific elimination of male-reactive CD8+ T cells in the lymph nodes. (iii) Four days after male lymphoid cells were injected intravenously into female transgenic mice, male antigen-reactive CD8+ T cells recovered from the lymph nodes of recipient mice were highly apoptotic when compared to CD4+ (non-male reactive) T cells. These data indicate that tolerance to extrathymic antigen can be achieved through elimination of mature T cells in the peripheral lymphoid organs.

Animals↗
PubMed1992

Rapid and long-term changes to host cytotoxic T lymphocyte precursors reactive to donor antigens caused by intravenous injection of histoincompatible lymphocytes.

It has been shown previously that a single intravenous injection of mouse F1 LNC into either parent results in a rapid reduction in the ability of the recipient to generate CTL reactive against donor antigens in an in vitro MLR. The underlying mechanism appears to be the inactivation of host CTL precursors that can recognize donor lymphocytes that have entered the recirculating pool. The donor lymphocytes may be acting as functionally deleting APC, or veto cells. Here, we have injected C57BL/6 (B6) mice with (C57BL/6 x DBA/2) F1 (F1) LNC. The CTL response against donor LNC was maximally reduced by 2 days and stayed reduced for at least 6 weeks, but ultimately recovered to normal levels. The response reduction mechanism remained operative during the period when the response was reduced: Fresh FITC-labeled B6 LNC introduced into B6 recipients of an earlier injection of F1 LNC were as effectively deleted of F1-reactive CTLp as the original host B6 LNC population, the fresh FITC-labelled B6 LNC being separated from host B6 LNC by cell sorting before testing. When B6 mice injected with F1 LNC ultimately recovered their response against F1 donor antigens, reinjection of F1 LNC did not induce a new response reduction. Instead of entering the recirculating pool, the injected F1 cells were rapidly removed by a specific immune process.

Animals↗
PubMed1992

Influence of human muscle length on energy transduction studied by 31P-NMR.

Muscle contractions at lengths below the optimum for force development were previously found to cause less fatigue than contractions at the optimum length (Lo). Decreased fatigability was suggested to arise from fewer cross-bridge interactions in shortened sarcomeres. In the present study, this suggestion was tested by monitoring energy use of human ankle dorsiflexor muscles during and after contractions at Lo and shortened lengths (Ls) with phosphorus nuclear magnetic resonance spectroscopy. The nuclear magnetic resonance spectra indicated similar rates of ATP use during contractions at Lo and Ls. Phosphocreatine, at an initial concentration of 37 mM, was reduced to an equivalent extent by 2 min of ischemic exercise at Lo (to 2.3 mM) and Ls (to 4.7 mM). Changes in pH (indicating glycolytic ATP production) were also equivalent at Lo and Ls. Exercise caused pH to fall from an initial level of 7.07 to 6.5 at Lo and to 6.53 at Ls. In relation to previous experiments performed under similar conditions on human ankle dorsiflexor muscles, the present experiments suggest that in shortened muscle the decreased force found in this and previous studies and the decreased fatigability that was previously found may not be simply due to fewer cross-bridge interactions in shortened sarcomeres. Examination of the relationships between developed force and levels of metabolites suggests that changes of force during fatigue and recovery correlate better with intracellular [Pi] and H2PO4- than with [H+].

Adenosine Triphosphate↗
PubMed1992

Mononeuritis multiplex associated with cryoglobulinemia in HIV infection.

We describe a patient with human immunodeficiency virus (HIV) infection who developed mononeuritis multiplex associated with polyclonal (type III) cryoglobulinemia. The patient's symptoms stabilized following treatment with plasmapheresis and removal of the cryoglobulin. Our case represents the first report of polyclonal cryoglobulinemia in HIV disease and suggests that cryoglobulinemia may play an etiologic role in some patients with HIV-associated neuropathy.

Adult↗
PubMed1991

In vivo functional clonal deletion of recipient CD4+ T helper precursor cells that can recognize class II MHC on injected donor lymphoid cells.

Intravenous injection of semiallogeneic (C57BL/6XDBA/2)F1 lymphocytes into adult C57BL/6 recipient mice not only, as previously reported, reduces the recipients' cytotoxic T lymphocyte response in a subsequent in vitro mixed lymphocyte reaction against the injected cell type, but also reduces Th cell function in the same MLR. Thus lymphoid cells derived from the injected mice were greatly reduced in their ability to proliferate and to produce IL-2 in response to (C57BL/6XDBA/2)F1 stimulator cells in vitro, whereas third party responses were unaffected. This appears to be due to a reduction in the precursor frequency of IL-2-producing T lymphocytes specific for the injected cells as measured by limiting dilution analysis. Similar donor-specific reduction in the frequency of precursors of IL-2-producing cells was seen after i.v. injection of A.TL lymphocytes into A.TH recipients (differing at class II determinants I-A and I-E, but identical at K and D). Here there also appeared to be a functional clonal deletion of precursors of IL-2-producing Th cells, shown directly to be class II MHC reactive and CD4+. There is strong evidence that the reduction of class I-specific cytotoxic responses in the injected mice is a manifestation of donor cells that function as veto cells, i.e., that function as deletional APC that inactivate class I-reactive CTL precursors that recognize them. Our data in this study show that class II-specific Th responses are similarly reduced in the injected mice and suggest that CD4+ class II-reactive precursors of Th cells may be functionally inactivated in vivo by donor cells via a veto-like mechanism.

Animals↗
PubMed1991

Depression of thymus-dependent immunity in wasting protein-energy malnutrition does not depend on an altered ratio of helper (CD4+) to suppressor (CD8+) T cells or on a disproportionately large atrophy of the T-cell relative to the B-cell pool.

We report cell numbers within major subsets of lymphocytes in the spleen, mesenteric nodes, and recirculating pool of weanling mice subjected to protein-energy malnutrition (PEM). PEM and thymus (T)-dependent immunodepression were induced in male C57BL/6J mice by a low-protein (LP) diet fed ad libitum. Recirculating lymphocyte numbers were estimated by enumerating labeled and unlabeled cells after equilibration of a known number of fluorescein isothiocyanate-labeled C57BL/6J donor lymphocytes within well-nourished or LP recipients. Involution of the recirculating lymphocyte pool of the LP group was proportionately less than the lymphoid atrophy of the spleen and mesenteric nodes. The LP protocol exerted no influence on the ratio of helper (CD4+) to suppressor (CD8+) T cells and increased the ratio of T cells to B cells in the secondary lymphoid organs and recirculating pool. These results challenge two established concepts: that T-dependent immunodepression in PEM depends on a reduced CD4(+)-CD8+ ratio and that PEM induces greater involution within the T-cell system than within the B-cell system.

Animals↗
PubMed1991

Prognosis in AZT myopathy.

The myopathy caused by zidovudine (AZT) appears to be common but is incompletely characterized, particularly regarding prognosis. Twenty patients with HIV infection developed a necrotizing myopathy while taking AZT for 9 to 30 months. Ten presented with myalgia and 17 with proximal muscle weakness. Serum CK was elevated in all (two to 11 times normal), and EMG suggested active myopathy in all but two. There were scattered granular degenerating fibers, with scant or no inflammation, in a pattern consistent with a toxic myopathy in all 18 patients biopsied. Three patients with an HIV-related inflammatory myopathy were distinguished by histologic differences. After stopping AZT (n = 15), myalgia promptly resolved (10 of 10). Strength improved more slowly with 12 of 15 regaining normal or nearly normal strength, but three have persistent weakness. CK returned to normal in 12 of 15, and follow-up EMG (n = 11) documented reduced fibrillation density in all 11 patients. These findings underscore the need for early diagnosis of this reversible myopathy.

Adult↗