Do calcium-dependent ionic currents mediate ischemic ventricular fibrillation?

Calcium ions mediate the adverse effects of myocardial ischemia and have been implicated in the genesis of arrhythmias. Calcium influx blocking drugs protect against early ventricular arrhythmias during experimental coronary occlusion, and recent studies suggest that this effect is at least partly due to inhibition of myocardial cell calcium influx. Most of the pharmacologic maneuvers used to simulate acute ischemic arrhythmias in vivo also produce intracellular calcium overload. Production of calcium overload in small myocardial cell clusters causes fibrillatory electrical and mechanical activity similar to that recorded from fibrillating hearts. Fibrillation in these cell clusters is mediated not by reentrant conduction, but by the same subcellular processes that give rise to depolarizing afterpotentials and abnormal automaticity. Agents favoring calcium influx, such as beta adrenergic agonists, accentuate these processes, while agents that depress calcium influx inhibit them. Although the relation of these experimental models to clinical ischemic arrhythmias has not been fully delineated, calcium influx blocking drugs may prove useful in reducing the incidence of sudden cardiac death.     

Pharmacologic therapy of ventricular arrhythmias

To treat patients with ventricular arrhythmias properly, one must characterize the arrhythmia, define the underlying heart disease and look for and treat reversible causes. When arrhythmias are suitable for pharmacologic suppression, it is necessary to predefine therapeutic goals, then carefully document that the drug accomplishes these goals. Knowledge of a drug's metabolism, excretion, active metabolites and plasma protein binding is often required for full understanding of its clinical effect. Pharmacokinetic principles require that antiarrhythmic drugs be given on a rigid schedule and that plasma drug levels be frequently determined. Use of compartment models and the principle of superposition can enable one to achieve and maintain therapeutic drug concentrations while avoiding toxic side effects. The drugs commonly used to treat arrhythmias, lidocaine, propranolol, procainamide, diphenylhydantoin and quinidine, as well as some newer agents, have specific pharmacokinetics and toxic effects that must be understood.     

Postreceptor alterations in the states of insulin resistance

Insulin-resistant adipose and muscle tissues of obese animals are characterized by decreases in insulin sensitivity and responsiveness. The decreased sensitivity is represented only by a shift to the right of the insulin dose-response curve and is due to the observed decrease in the number of insulin receptors of these target tissues. The decreased responsiveness to insulin is manifested by a decrease in the maximal response to even supramaximal concentrations of the hormone. In both adipose and muscle tissues, maximal responses to insulin are achieved with only a minority of receptor sites filled (i.e., they have “spare” receptors). Given that the observed decrease in the number of insulin receptors of insulin-resistant target cells never exceeds that of the “spare” receptors, insulin-resistant adipose and muscle tissues should have enough remaining insulin-binding sites to permit maximal stimulatory effects at maximal insulin concentrations. Consequently, the observed decreased insulin responsiveness of these tissues cannot be attributed to a decreased number of receptors but can be shown to be caused by abnormalities distal to the insulin-receptor interaction. In adipose tissue, distal abnormalities are numerous, although they do not include the glucose transport system per se. In muscle tissue, distal abnormalities are also multiple but do include glucose transport and phosphorylation. Refeeding, fasting, and a high-carbohydrate or a high-fat diet can also be shown to produce metabolic alterations that are distal to the insulin-receptor interaction.     

Exogenous stress proteins enhance the immunogenicity of apoptotic tumor cells and stimulate antitumor immunity

We have previously reported that apoptotic tumor cells can be either immunogenic or nonimmunogenic in vivo, depending on whether or not these cells are heat stressed before induction of apoptosis. Stressed apoptotic cells express heat shock proteins on their plasma membranes and dendritic cells are capable of distinguishing them from nonstressed apoptotic cells. Here we provide evidence that when purified heat shock protein 70 or chaperone-rich cell lysate (CRCL) from syngeneic normal tissue is used as an adjuvant with nonimmunogenic apoptotic tumor cells in vaccination, potent antitumor immunity can be generated. This antitumor immunity is mediated by T cells because antitumor effects are not observed in either severe combined immunodeficiency or T cell-depleted mice. We further demonstrate that vaccination of mice with apoptotic tumor cells mixed with liver-derived CRCL as adjuvant were capable of enhancing the production of T(H)1 cytokines, inducing specific cytotoxic T lymphocytes and eliciting long-lasting antitumor immunity. Stress proteins from autologous normal tissue components therefore can serve as danger signals to enhance the immunogenicity of apoptotic tumor cells and stimulate tumor-specific immunity     

Characterization of renal tissue lymphocytes in patients with interstitial nephritis

Five patients with interstitial nephritis who presented with a variety of clinical profiles were studied with particular emphasis on documentation of the cellular types of potentially immunocompetent lymphocytes and mononuclear cells present within interstitial renal infiltrates. Immunohistologic studies coupled with conventional light and electron microscopic observations indicated that most mononuclear cells making up renal interstitial infiltrates were T cells. Some chronic inflammatory cell foci within renal interstitium were characterized by clusters of Ia antigen-positive T cells considered to be markers for activated lymphocytes. B cells were present in very small proportions (5 percent or less). The profile of immunocompetent cells present in lesions of interstitial nephritis suggests a major role for cell-mediated immunity in this disorder. Increase in tissue lymphocytes of the Tγ subclass with receptors for the Fc portion of immunoglobulin G (IgG) also suggests local activation of intrinsic suppressor cell mechanisms.     

Remission and recovery from chronic, established, complete heart block.

The return of A-V conduction is described in a patient after two decades of high-grade or complete congenital heart block. Similar cases have been reported by others, with remission or even recovery commencing up to the fourth decade or later. A similar phenomenon is also described in four patients with acquired heart block of four to ten years' duration; in them, remission was usuallly brief but persisted for seven years in one patient. No full report of this seems to have been published previously. Possible explanations are discussed, but no conclusion is reached. Apart from its interest, the phenomenon is of importance with respect to the selection of demand-type electronic pacemakers in the management of patients with heart block.     

Differing thyrotropin responses to increased serum triiodothyronine concentrations produced by overfeeding and by triiodothyronine administration

The effects of overfeeding and triiodothyronine (T3) administration on basal serum thyrotropin (TRH) concentrations and the TSH response to thyrotropin-releasing hormone (TRH) was studied in normal subjects. Eight normal volunteers were fed their usual diet plus 2,000 kcal carbohydrate daily for 7 days. Their mean serum T3 concentrations increased from 102 +/- 6 (SEM) ng/dl to 126 +/- 10 ng/dl; there were no changes in serum thyroxine (T4) and basal serum TSh concentrations or the TSh response to TRH. Five of these subjects were fed their usual diet plus 10 micrograms T3 for 3 days and 20 micrograms T3 for 4 days divided doses. Their mean serum T3 concentrations increased from 104 +/- 6 ng/dl to 140 +/- 8 ng/dl. Mean serum T4 and basal serum TSH concentrations declined and serum TSH responses to TRH were significantly reduced. In both instances serum T3 concentrations remained within the normal range. These results indicate that increases in serum T3 concentrations of similar magnitude induced by augmented extrathyroidal T3 production and T3 administration have different effects on thyrotroph function.     

1,25-dihydroxyvitamin D resistance,rickets, and alopecia

Two unrelated kindreds with four affected children having 1,25-dihydroxyvitamin D resistance, rickets, and alopecia are described. The children exhibited early onset of severe rickets with hypocalcemia, hypophosphatemia, elevated serum alkaline phosphatase levels, and secondary hyperparathyroidism. Radiography showed diffuse demineralization and classic changes of rickets. All affected children had total-body alopecia. Serum levels of 1,25-dihydroxyvitamin D₃ were elevated and rose to extremely high values during treatment, with no apparent change in the mineral disorder. However, secondary hyperparathyroidism and hypophosphatemia did remit during treatment despite persistently low calcium levels. Skin biopsy was performed in the parents and affected children in one kindred. Analysis of 1,25-dihydroxyvitamin D₃ receptors in cultured fibroblasts Indicated apparent normal receptors in the parents and undetectable receptors In both affected children. After long periods of treatment with vitamin D metabolites and mineral replacement, healing took place in the older child in each kindred. These data suggest that the healing occurred spontaneously as the children reached seven to nine years of age rather than as a result of the treatment. The biochemical lesion in these children appeared to be a genetically transmitted defect in the 1,25-dihydroxyvitamin D₃ receptor. The mechanisms by which healing was initiated and maintained remain to be elucidated.     

Crosstalk between innate and adaptive immunity in hepatitis B virus infection

Hepatitis B virus(HBV) infection is a major public healthproblem worldwide. HBV is not directly cytotoxic to infected hepatocytes; the clinical outcome of infection results from complicated interactions between the virus and the host immune system. In acute HBV infection, initiation of a broad, vigorous immune response is res-ponsible for viral clearance and self-limited inflammatory liver disease. Effective and coordinated innate and adaptive immune responses are critical for viral clearance and the development of long-lasting immunity. Chronic hepatitis B patients fail to mount efficient innate and adaptive immune responses to the virus. In particular, HBV-specific cytotoxic T cells, which are crucial for HBV clearance, are hyporesponsiveness to HBV infection. Accumulating experimental evidence obtained from the development of animal and cell line models has highlighted the importance of innate immunity in the early control of HBV spread. The virus has evolved immune escape strategies, with higher HBV loads and HBV protein concentrations associated with increasing impairment of immune function. Therefore, treatment of HBV infection requires inhibition of HBV replication and protein expression to restore the suppressed host immunity. Complicated interactions exist not only between innate and adaptive responses, but also among innate immune cells and different components of adaptive responses. Improved insight into these complex interactions are important in designing new therapeutic strategies for the treatment HBV infection. In this review, we summarize the current knowledge regarding the cross-talk between the innate and adaptive immune responses and among different immunocytes in HBV infection.     

Comparative mechanisms of action of antiarrhythmic drugs

The antiarrhythmic actions of different compounds are best compared in terms of their dominant electrophysiologic effects on myocardial fibers from different parts of the heart. Such primary actions may be modified considerably by changes in the serum electrolyte concentrations, pH, interactions with serum proteins, or other extracardiac factors. Clinically, however, it appears useful to categorize antiarrhythmic drugs into four groups in terms of their currently known mechanisms of action. Quinidine is the prototype of Group 1 drugs. Its main effect is the reduction of the maximal rate of depolarization of the cardiac action potential so that it slows conduction velocity and increases the effective refractory period with only minor effects on repolarization. Procainamide, disopyramide, carbamazepine, and Kö 1173 all have similar effects to those of quinidine on heart muscle. Lidocaine and diphenylhydantoin may be considered to constitute a subgroup (Group 1B) of “quinidine-like” drugs. In small concentrations they increase membrane responsiveness but in concentrations in the therapeutic range they have a quinidine-like depressant action on the cardiac membrane, particularly if serum levels of potassium are physiologically appropriate. Group 2 drugs are exemplified by β-adrenergic receptor blocking compounds. In blocking concentrations their only electrophysiologic effect is the reduction in the slope of the pacemaker potential; in very much higher concentrations they reduce the maximal rate of depolarization of the cardiac action potential but the precise clinical significance of this is still uncertain. Amiodarone and bretylium prolong the duration of the action potential in the ventricular muscle and Purkinje fibers without causing a significant change in other electrophysiologic parameters. This leads to a “pure” prolongation of the absolute refractory period which may be regarded as an independent antiarrhythmic mechanism (Group 3). Verapamil, a novel antiarrhythmic compound, is a specific calcium antagonist in the heart. It does not reduce the maximal rate of depolarization of the action potential but slows the spontaneous diastolic depolarization in heart muscle. The effects of verapamil are sufficiently different from those of other known agents to allow the tentative conclusion that its fundamental mode of action represents a fourth (Group IV) class of antiarrhythmic action.     

Electrophysiologic studies in the denervated transplanted human heart: II. Response to norepinephrine, isoproterenol and propranolol

Five patients who had received a transplanted human heart 1 to 3 years previously were studied to determine the effects of norepinephrine, isoproterenol and propranolol on the atrioventricular (A-V) conduction system. Using the His bundle technique, atrial, His bundle and ventricular electrograms were recorded, and central aortic pressure was monitored during the administration of these drugs. Norepinephrine was given by continuous infusion to four patients in doses ranging from 4 to 8 μg/min, with the systolic arterial pressure increasing by an average of 72 mm Hg. Concomitantly, there was an average increase in the rate of the donor atrium of 32 beats/min, and a reflex slowing of the recipient atrium of 23 beats/min. The A-H interval shortened by an average of 27 msec. Isoproterenol dose-response curves were performed in three patients, with the maximal dose being 5.2 μg by intravenous bolus infusion. The rate of the donor atrium increased by an average of 40 beats/min, and that of the recipient atrium by 18 beats/ min. The A-H time shortened by an average of 25 msec, with a drop in systolic blood pressure averaging 23 mm Hg. Propranolol (7 mg intravenously) was given to three patients and the peak doses of norepinephrine and isoproterenol were again infused. Beta adrenergic blockade was achieved at this dose of propranolol since there was only a minimal increase in the donor atrial rate after infusion of the drug. The A-H interval was not altered by catecholamine infusion after achievement of beta blockade. However, the levels of systolic hypertension noted after infusion of norepinephrine were not altered by propranolol. The denervated transplanted human heart appears to respond normally to norepinephrine and isoproterenol, and the electrophysiologic effects of these agents are blocked by propranolol.

Extensive investigative work in the denervated canine model has demonstrated the presence of the alpha and beta cardiovascular receptors. Although the autonomic nervous system is important in cardiac performance, this work is the first validation in man that (1) the functional integrity of the beta receptor is maintained even when the autonomic nerves are absent, and (2) the intrinsic properties of the sinus and atrioventricular nodes are the keystone in stabilizing cardiac electrophysiology after denervation.     

Tocainide for drug-resistant ventricular arrhythmias: Efficacy,side effects,and lidocaine responsiveness for predicting tocainide success

Tocainide therapy has been evaluated in 38 patients with ventricular arrhythmias. Thirty-one had recurrent sustained ventricular tachycardia and/or fibrillation and 29 required prior cardioversions. These arrhythmias could not be managed with quinidine, procainamide, disopyramide, or propranolol. Tocainide doses averaged 1,500 mg/day (range 600 to 2,400) and the majority of patients had plasma concentrations from 6 to 12 μg/ml. Twenty-two patients (61%) had their arrhythmias controlled with tocainide and 16 (39%) did not. Tocainide dose and plasma concentrations were similar for responders and nonresponders. Lidocaine was effective in 26 patients and 16 (63%) of these had their arrhythmias controlled with tocainide. Of 12 patients in whom lidocaine was known to be ineffective or who had not been previously treated, only two (17%) had arrhythmias controlled with tocainide (P < 0.02). Side effects occurred in approximately two thirds of patients but required discontinuation of long-term tocainide in only three patients.     

Activation of NK cell granulysin by mycobacteria and IL-15 is differentially affected by HIV

NK cells play an important role in innate immunity to mycobacteria and are a significant source of the bactericidal effector molecule granulysin. Defects in NK cells have been described in HIV-infected patients, though mechanistic studies have focused on effector molecules relevant to anti-viral, and not anti-bacterial, function. Here we used primary NK cells from healthy human donors and an in vitro system to identify the phenotype of granulysin expressing NK cells, characterize activation stimuli that regulate granulysin, and to study the immediate effects of HIV on innate activation of NK cell granulysin expression. We observe that granulysin expression is co-associated with cytotoxicity receptors (NKp46, NKG2D) known to have important function in the cytotoxic response to M.tb-infected macrophages. Granulysin expression is significantly increased following exposure to IL-15 or Mycobacterium bovis BCG, but in contrast to our previous findings with CD8(+)T cells, expression is weakly activated by IL-21. Infection of PBMC with HIV-1 suppresses NK cell induction of granulysin by IL-15, but does not impair activation by BCG. These effects of HIV-1 are associated with reduced STAT5 phosphorylation in the IL-15 activated signaling cascade. These observations suggest that HIV may impair the anti-bacterial function of NK cells and have implications for clinical use of IL-15 to augment innate cell mediated immunity in HIV+ patients.     

Antigen-independent memory CD8 T cells do not develop during chronic viral infection

Memory T cells can persist for extended periods in the absence of antigen, and long-term T cell immunity is often seen after acute infections. Paradoxically, there have been observations suggesting that T cell memory may be antigen-dependent during chronic infections. To elucidate the underlying mechanisms we have compared memory CD8 T cell differentiation during an acute versus chronic infection by using the mouse model of infection with lymphocytic choriomeningitis virus. We found that during a chronic infection virus-specific CD8 T cells failed to acquire the cardinal memory T cell property of long-term antigen-independent persistence. These chronically stimulated CD8 T cells were unable to undergo homeostatic proliferation, responded poorly to IL-7 and IL-15, and expressed reduced levels of the IL-7 and IL-15 receptors, thus providing a possible mechanism for the inability of these cells to persist long term in the absence of antigen. In striking contrast, virus-specific memory CD8 T cells that developed after an acute lymphocytic choriomeningitis virus infection could persist without antigen, were capable of self-renewal because of homeostatic proliferation, responded efficiently to IL-7 and IL-15, and expressed high levels of receptors for these two cytokines. Thus, memory CD8 T cells generated after acute infections are likely to have a competitive advantage over CD8 T cells that develop during chronic infections. These findings raise concerns about using vaccines that may persist and also suggest that there may be limitations and challenges in designing effective immunological interventions for the treatment of chronic infections and tumors.     

Insulin receptors of skeletal muscle: specific insulin binding sites and demonstration of decreased numbers of sites in obese rats.

A membrane preparation was obtained from rat striated muscle. The preparation used has been shown to contain plasma membranes by electron microscopy as well as by enrichment in specific activity of both a plasma membrane enzyme "marker" (5'-nucleotidase) and cell surface 125I-incorporated radioactivity. The characteristics of 125I-insulin binding to this striated muscle preparation were studied, and it was found that 125I-insulin readily and specifically binds to this membrane preparation. The binding reaction was time, pH, and temperature dependent with optimal steady-state binding conditions occurring at 20 degrees C and at pH 7.6. Under these conditions (20 degrees C, pH 7.6) skeletal muscle plasma membranes displayed little ability to degrade insulin. Binding of 125I-insulin was readily inhibited at physiologic concentrations of unlabeled insulin and the specificity of this receptor for insulin was demonstrated by finding that high concentrations of glucagon, b-LH, b-FSH, p-PRL, hCG, TSH, and HGH were without effect on 125I-insulin binding and that insulin analogues inhibited binding in proportion to their biologic activity. When membranes from older, fatter rats were compared to membranes from younger, lean animals, 5'-nucleotidase specific activity and insulin degrading activity were found to be comparable. On the other hand, insulin binding to membrane receptors was decreased 30%-40% in the older, fatter animals. Thus, these studies indicate that (1) specific insulin receptors exist in skeletal muscle plasma membranes, and (2) membranes from older, fatter rats have fewer receptors than those from younger, lean animals.     

In vivo manipulation of dendritic cells to induce therapeutic immunity

Efficient antigen presentation and T-cell priming are essential components of effective antitumor immunity. Dendritic cells are critical to both of these functions but to date no method has been devised that both targets antigen to these cells and activates them, in situ, in a manner that induces systemic immunity. In this study we combined a dendritic cell growth factor, Flt3 ligand, with a dendritic cell activator, immunostimulatory DNA, and a tumor antigen to activate and load dendritic cells in vivo. Initial studies showed that immunostimulatory DNA not only activates dendritic cells but also prolongs their survival in vivo and in vitro. Following treatment of mice with Flt3 ligand, coadministration of immunostimulatory DNA and antigen induced potent antitumor immunity, resulting in both tumor prevention and regression of existing tumors. CD8 cytotoxic T lymphocytes but not CD4 T cells were required for tumor protection. Natural killer cells also contributed to tumor protection. These results show that dendritic cells can be loaded with antigen and activated, in situ, and provide the basis for dendritic cell- targeted clinical strategies.     

Tuberculosis: recent progress in basic immunity and vaccine development

Tuberculosis continues to be the most prevalent cause of death from an infectious agent globally, and its interaction with HIV is having devastating effects, particularly in Sub-Saharan Africa. Over the past decade, my laboratory has developed small animal models of pulmonary infection, which have revealed new information regarding the nature of acquired immunity, and subsequent immunopathology, in the lungs. We propose that cell mediated immunity comprises two separate elements; protective immunity, driven by IL-12 and IFN; and DTH, mediated by TNF and driven by chemokines. The generation of a CD4 response is critical to both processes, but other cells are also involved in the overall control of the infection. These include gamma delta T cells, which we believe control the inflammatory influx of cells; CD4+ NK cells, which may play a role in focussing lymphocytes into lung granulomas; and CD8 T cells, which play a currently undefined role after initial expression of immunity and establishment of chronic disease in the lungs has ensued. Complex interactions between these populations of cells appear to control the influx of mediator cells into the lungs and then focus them at sites of infection. Prior to adequate expression of protective immunity the correct expression of chemokine and adhesion molecules is critical. A better understanding of these processes will hopefully in turn lead to better vaccine design, a topic which is also addressed in this paper.     

Estimating prognosis in systemic lupus erythematosus

Knowledge of prognosis is critical for rational choice of therapy. Systemic lupus erythematosus, with its broad clinical spectrum, presents an example of the problem of prognostication for the individual patient. The life table method can provide prognostic information. It need not be limited to estimation of survivorship, and its utility can be multiplied by a computer databank. Analysis of prognosis for different groups of patients, from different events in their course, over different time periods, and to different end points can then be performed. Using this technic, specific clinical variables in systemic lupus erythematosus were assessed for their effect upon particular outcomes. Clinical variables representing functional organ impairment were found to carry a worse prognosis than the popular serologic indicators. New abnormalities were found to occur less frequently in later years of the disease. Different subpopulations of patients have strikingly different expectations, and these differences carry important therapeutic implications.     

Diversity of NKR expression in aging T cells and in T cells of the aged: the new frontier into the exploration of protective immunity in the elderly

Aging in the immune system is characterized by the contraction of the lymphocyte repertoire, exemplified by long-lived oligoclonal T cells that pervade the peripheral circulation. T-cell receptor (TCR) repertoire contraction likely explains the decline in immunity with chronological age as evidenced by the increased morbidity and mortality to common and new infections, and the low rates of protective responses to vaccination in the elderly. Interestingly, in vitro senescence models and cross sectional ex vivo studies have consistently demonstrated that senescent (or pre-senescent) T cells and T cells of the aged express unusually high densities of receptors that are normally found on natural killer (NK) cells, the killer cell immunoglobulin-like receptors (KIR) being the most diverse NK receptors (NKR). Molecular studies also show that T cells are programmed to express NKRs/KIRs, and T-cell clonal lineages express a variety of NKRs towards the end stages of their replicative lifespan. We propose that NKR/KIR induction in aging T cells is an adaptational diversification of the immune repertoire. We suggest that NKR/KIR expression in oligoclonal senescent and pre-senescent T cells is a compensatory adaptation to maintain immune competence despite the overall contraction in TCR diversity with aging. NKRs comprise a diverse superfamily of receptors. Mounting evidence for NKR/KIR signaling pathways in T cells divergent from those seen in NK cells indicate that senescent NKR(+)T cells are unique immune effectors. We suggest that appreciation of the functional diversity of these unusual NK-like T cells is central to the creative development of new strategies to enhance protective immunity in the aged.     

Prognostic discrimination for early chronic phase chronic myeloid leukemia in imatinib era: comparison of Sokal,Euro, and EUTOS scores in Korean population

Adoptive transfer of tumor-reactive T cells into cancer patients with the intent of inducing a cytotoxic anti-tumor effector response and durable immunity has long been proposed as a novel therapy for a broad range of malignancies; however, local and systemic tolerance mechanisms have hindered the generation of effective T cell therapies and limited the clinical efficacy of this approach in cancer patients. Chimeric antigen receptors (CARs) are recombinant receptors that comprise an extracellular antigen-targeting domain in conjunction with one or more intracellular T cell signaling domains that can be introduced into T cells by genetic modification to redirect their specificity to the CAR-targeted antigen. Administration of CD19-specific CAR-modified T cells that target B cell non-Hodgkin lymphomas and leukemia has been remarkably effective in recent clinical trials, energizing the field and stimulating new efforts to identify the critical parameters of CAR design and T cell engineering that are necessary for effective cancer therapy.