Etanercept therapy in rheumatoid arthritis. A randomized, controlled trial

BACKGROUND

In a phase II study, etanercept (recombinant human tumor necrosis factor receptor [p75]:Fc fusion protein) safely produced rapid, dose-dependent improvement in rheumatoid arthritis over 3 months.

OBJECTIVE

To confirm the benefit of etanercept therapy of longer duration and simplified dosing in patients with rheumatoid arthritis.

DESIGN

Randomized, double-blind, placebo-controlled trial with blinded joint assessors.

SETTING

13 North American centers.

PATIENTS

234 patients with active rheumatoid arthritis who had an inadequate response to disease-modifying antirheumatic drugs.

INTERVENTION

Twice-weekly subcutaneous injections of etanercept, 10 or 25 mg, or placebo for 6 months.

MEASUREMENTS

The primary end points were 20% and 50% improvement in disease activity according to American College of Rheumatology (ACR) responses at 3 and 6 months. Other end points were 70% ACR responses at 3 and 6 months and other measures of disease activity at 3 and 6 months.

RESULTS

Etanercept significantly reduced disease activity in a dose-related fashion. At 3 months, 62% of the patients receiving 25 mg of etanercept and 23% of the placebo recipients achieved 20% ACR response (P < 0.001). At 6 months, 59% of the 25-mg group and 11% of the placebo group achieved a 20% ACR response (P < 0.001); 40% and 5%, respectively, achieved a 50% ACR response (P < 0.01). The respective mean percentage reduction in the number of tender and swollen joints at 6 months was 56% and 47% in the 25-mg group and 6% and -7% in the placebo group (P < 0.05). Significantly more etanercept recipients achieved a 70% ACR response, minimal disease status (0 to 5 affected joints), and improved quality of life. Etanercept was well tolerated, with no dose-limiting toxic effects.

CONCLUSIONS

Etanercept can safely provide rapid, significant, and sustained benefit in patients with active rheumatoid arthritis.

A revised estimate of twin concordance in systemic lupus erythematosus

OBJECTIVE

Based on a small clinical series and previously published case reports, concordance for systemic lupus erythematosus (SLE) among monozygous (MZ) twins has been reported to be as high as 69%. Using a larger and less biased sample, we provide another estimate of this percentage.

METHODS

We established a registry of twins with SLE, based upon self-reports and information provided by the patients' physicians. We used DNA fingerprinting to validate the reported zygosity in a sample of these twins.

RESULTS

Of 107 twin pairs meeting the American College of Rheumatology 1982 revised criteria for the diagnosis of SLE, 24% of 45 MZ pairs and 2% of 62 dizygous (DZ) pairs were concordant. The frequency distributions of diagnostic criteria and disease symptoms in the SLE patients were similar to those in other published reports of SLE patients. Zygosity was confirmed by DNA fingerprinting in a subsample of 15 self-described MZ twins and 7 self-described DZ twins. All individuals had correctly predicted their zygosity.

CONCLUSION

MZ concordance for SLE is similar to that for other autoimmune diseases and is much lower than previously believed.

A role for TGF-beta in the generation and expansion of CD4+CD25+ regulatory T cells from human peripheral blood

An elusive goal in transplanting organs across histocompatibility barriers has been the induction of specific tolerance to avoid graft rejection. A considerable body of evidence exists that the thymus produces regulatory T cells that suppress the response of other T cells to antigenic stimulation. We report that TGF-beta can induce certain CD4+ T cells in the naive (CD45RA+RO-) fraction in human peripheral blood to develop powerful, contact-dependent suppressive activity that is not antagonized by anti-TGF-beta or anti-IL-10 mAbs. The costimulatory effects of TGF-beta on naive CD4+ T cells up-regulated CD25 and CTLA-4 expression, increased their transition to the activated phenotype, but decreased activation-induced apoptosis. Suppressive activity was concentrated in the CD25+ fraction. These CD4+CD25+ regulatory cells prevented CD8+ T cells from proliferating in response to alloantigens and from becoming cytotoxic effector cells. Moreover, these regulatory cells exerted their suppressive activities in remarkably low numbers and maintained these effects even after they are expanded. Once activated, their suppressive properties were Ag nonspecific. Although <1% of naive CD4+ T cells expressed CD25, depletion of this subset before priming with TGF-beta markedly decreased the generation of suppressive activity. This finding suggests that CD4+CD25+ regulatory T cells induced ex vivo are the progeny of thymus-derived regulatory T cells bearing a similar phenotype. The adoptive transfer of these regulatory T cells generated and expanded ex vivo has the potential to prevent rejection of allogeneic organ grafts.

Depressed cell-mediated immunity in patients with primary intracranial tumors. Characterization of a humoral immunosuppressive factor

Tumor immunity in patients with primary intracranial tumors was assessed in relation to the general status of host immunocompetence. Lymphocyte sensitization to tumor-specific membrane antigens was demonstrated by the proliferative response of lymphocytes in the presence of autochthonous tumor cells. Paradoxically, one-half of the patients could not be sensitized to a primary antigen, dinitrochlorobenzene; existing delayed hypersensitivity was also depressed, as measured by skin tests and lymphocyte transformation in response to common antigens. A heat-stable factor in patients' sera blocked cell-mediated tumor immunity. In addition, these "enhancing" sera consistently suppressed the blastogenic response of autologous and homologous lymphocytes to phytohemagglutinin and to membrane antigens on allogeneic cells in the one-way mixed lymphocyte culture. When patients' leukocytes were washed and autologous plasma replaced with normal plasma, reactivity in the mixed lymphocyte culture increased to normal values. In vitro immunosuppressive activity in patients' plasma or sera correlated with depressed delayed hypersensitivity. After removal of the tumor, suppressor activity disappeared. IgG fractions of patient sera contained strong immunosuppressive activity. These data suggest that the suppressor factor may be an isoantibody elicited by the tumor that also binds to receptors on the lymphocyte membrane. In addition to specifically blocking cell-mediated tumor immunity, enhancing sera may broadly depress host immunocompetence.

Urinary kallikrein excretion in normal man. Relationships to sodium intake and sodium-retaining steroids

The urinary excretion of kallikrein, a renal enzyme that cleaves the potent vasodilator kinin, kallidin, from kininogen, was measured in normal volunteers by three different assays, one of which was a bioassay. When sodium intake was changed from ad libitum or 109 mEq/day to 9 mEq/day, daily kallikrein excretion increased progressively in every subject to a mean maximal value that was 271% of control by day 7; an increase in sodium intake to 259 mEq/day resulted in the return of kallikrein excretion to control values. Urinary excretion of amylase, a protein with a molecular weight similar to that of kallikrein, did not change when sodium intake was changed, but plasma renin activity and aldosterone excretion changed appropriately. In subjects on a constant-sodium (109 mEq/day), constant-potassium (100 mEq/day) diet, fludrocortisone, 0.5 mg/day for 10 days, increased kallikrein excretion to a mean maximal value that was 203% of control. In subjects on a diet containing 9 mEq sodium/day, elevated kallikrein excretion decreased during treatment with spironolactone, 400 mg/day. Rapid administration of water (1 or 2 liters in 30 minutes, orally) or rapid infusion of 2.4 liters of normal saline did not significantly alter urinary kallikrein excretion despite large changes in urine volume or sodium excretion. Thus, kallikrein excretion appears to be directly related to the effective level of circulating sodium-retaining steroid. The findings are consistent with a role for the kallikrein-kinin system in the renal response to sodium-retaining hormones.

Decreased production of interleukin-12 and other Th1-type cytokines in patients with recent-onset systemic lupus erythematosus

OBJECTIVE

To determine the profile of Th1-type and Th2-type cytokines produced by mononuclear cells from patients with recent-onset systemic lupus erythematosus (SLE), prior to the initiation of treatment with corticosteroids.

METHODS

Using sensitive radioimmunoassays, interleukin-4 (IL-4), IL-10, IL-12 p40, tumor necrosis factor alpha (TNF alpha), interferon-gamma (IFN gamma), and granulocyte-macrophage colony-stimulating factor (GM-CSF) released into the culture supernatants of various unstimulated and stimulated blood mononuclear cell populations from 10 SLE patients was assessed in comparison with 10 matched healthy controls studied in parallel.

RESULTS

In early SLE, monocyte-enriched cells constitutively produced increased amounts of IL-10 and decreased amounts of IL-12 following stimulation. Lymphocyte-enriched cells in SLE produced decreased amounts of IFN gamma and TNF alpha following stimulation. In "rested" cells, these defects were accentuated and a defect in IL-12 production was suggested. Depletion studies suggested that CD8+ cells were a major source of TNF alpha and IFN gamma in controls, but not in SLE patients. Increased IL-4 production or abnormalities in GM-CSF production were not observed.

CONCLUSION

This study suggests that even early in the course of SLE, monocyte production of IL-10 is increased and that of IL-12 is decreased. Decreased production of Th1-type cytokines in SLE may be secondary to this imbalance between IL-10 and IL-12. A contributory role of dysfunctional CD8+ cells is suggested.

Urinary kallikrein excretion in hypertensive man. Relationships to sodium intake and sodium-retaining steroids

Urinary kallikrein excretion was measured by a radiochemical esterolytic assay in patients with essential hypertension or primary aldosteronism. Patients with essential hypertension excreted significantly less ( P < 0.001) kallikrein than did normal subjects when they were allowed an ad libitum sodium intake or given 259 mEq sodium/day. When sodium intake was changed from ad libitum to 9 mEq/day, kallikrein excretion increased in the majority of patients with essential hypertension, but it remained significantly less ( P < 0.001) than that in normal subjects; however, aldosterone excretion was similar in both groups. Fludrocortisone, 0.5 mg/day for 10 days, increased kallikrein excretion in three patients with essential hypertension. In patients with primary aldosteronism, mean kallikrein excretion was sevenfold higher ( P < 0.001) than that in patients with essential hypertension; kallikrein excretion remained unchanged when dietary sodium was altered, but it was decreased by treatment with spironolactone. Mean kallikrein excretion in patients with primary aldosteronism was also significantly higher ( P < 0.001) than that in a normotensive control population. The results show that kallikrein excretion reflects the effective level of circulating sodium-retaining steroid in patients with primary aldosteronism but suggest that it is relatively unresponsive to endogenous sodium-retaining steroid in patients with essential hypertension. The data raise the possibility that the kallikrein-kinin system is of pathogenetic significance in human hypertensive disease.

Evidence by reactivity with hybridoma antibodies for a probable myeloid origin of peripheral blood cells active in natural cytotoxicity and antibody-dependent cell-mediated cytotoxicity

Lymphocytes with Fc receptors (FcR) for IgG active in natural cytotoxicity and antibody-dependent cellular cytotoxicity were separated into sheep erythrocyte rosetting (E+) and nonrosetting (E-) fractions, and examined for reactivity with the OK panel of hybridoma-produced monoclonal antibodies. Few cells in either the E+ FcR+ or the E- FcR+ fraction reacted with seven antibodies used to define T cells in various stages of differentiation (OK3, OKT4, OKT5, OKT6, OKT8, OKT9, OKT10). Neither fraction expressed an Ia-like antigen (detected by OKI1), but both were highly reactive with OKM1, an antibody that reacts with monocytes and granulocytes. Incubation of these cytotoxic effector cells with OKM1 plus complement abolished all cytotoxic reactivity, but incubation with a pan-T cell antibody (OKT3) plus complement had no significant effect. These cells were not monocyte precursors, because they could not be induced in vitro to develop macrophage characteristics. The data indicate that most cytotoxic effector cells in natural cytotoxicity and antibody-dependent cellular cytotoxicity are not in the T cell lineage, but have a myeloid origin.

Biochemical and pharmacologic effects of alpha-methyltyrosine in man

Alpha methyltyrosine (alpha-MPT) was administered to 52 patients from 4 days to 10 months; 22 patients were cases of pheochromocytoma and 20 had essential hypertension. Inhibition of catecholamine synthesis in the range of 50-80% was achieved with divided daily drug dosage of from 1.0 to 4.0 g. Striking clinical benefit was noted in patients with pheochromocytoma in whom the drug was used in preparation for surgery and during chronic medical management. The drug appeared to have limited usefulness when used in essential hypertension, unless added to existing therapy with conventional agents. No beneficial effects were noted in thyrotoxicosis, glaucoma, and Raynaud's phenomenon. Untoward effects in order of decreasing incidence were: sedation (with insomnia on withdrawal), anxiety, tremor, diarrhea, and galactorrhea. Drug crystalluria, which has been observed in animals and is currently restrictive of clinical trials, was not observed in these studies. Evidence is presented that the minor conversion of alpha-MPT to methyldopa probably does not contribute significantly to the central and peripheral effects of the drug.

Methyldopa inhibition of suppressor-lymphocyte function: a proposed cause of autoimmune hemolytic anemia

To test the hypothesis that methyldopa induces red-cell autoantibodies by inhibiting the activity of suppressor lymphocytes, we studied its effect on several immune functions. Methyldopa inhibited T-lymphocyte suppression of IgG production by peripheral-blood mononuclear cells stimulated by poke-weed mitogens. This effect occurred in isolated T cells incubated with methyldopa and in T cells obtained from patients taking methyldopa. In addition, the drug caused a 30 to 80 per cent reduction in the proliferative response of peripheral-blood mononuclear cells to mitogens in vitro, and this reduction primarily involved the activation of T lymphocytes. Methyldopa also caused a persistent elevation of intracellular lymphocyte cyclic AMP in vitro and in vivo. We postulate that methyldopa alters the immune system by causing a persistent increase in lymphocyte cyclic AMP, which inhibits suppressor T-cell function. These effects may lead to unregulated autoantibody production by B cells in some patients.

The role of transforming growth factor beta in the generation of suppression: an interaction between CD8+ T and NK cells

CD8+ T cells have suppressor effector functions, but the mechanisms involved in the generation of this activity are poorly understood. We report that natural killer (NK) cells have an important role in the acquisition of this function. CD8+ cells induce NK cells to produce transforming growth factor-beta (TGF-beta) which, in turn, stimulates CD8+ T cells to become suppressors of antibody production. Using a monocyte-dependent and -independent method to induce antibody production, we first observed that the addition of NK cells to CD8+ cells was required for optimal suppression. Next, we determined that the interaction of CD8+ T cells with NK cells resulted in a striking increase NK cell TGF-beta mRNA and its production. This cytokine appeared to be involved in the induction of T suppressor cell activity since: (a) anti-TGF-beta 1 completely abrogated the suppression of immunoglobulin G synthesis; (b) TGF-beta 1 could substitute for NK cells in inducing CD8+ T cells to develop suppressor activity; and (c) a short exposure of T cells to TGF-beta 1 in the absence of B cells was sufficient for the generation of suppressor activity by CD8+ T cells. Interferon gamma did not have this property. These studies provide strong evidence that in addition to its suppressive properties, TGF-beta is involved in the generation of CD8+ T suppressor effector cells. Because NK cell function is decreased in many autoimmune diseases, these cells may fail to interact properly with these individuals' CD8+ cells in generating suppressors of aggressive anti-self responses.

Synergistic effect between IL-10 and bcl-2 genotypes in determining susceptibility to systemic lupus erythematosus

OBJECTIVE

To determine whether genes participating in programmed cell death, including bcl-2, IL-10, Fas-L, and CTLA-4, may contribute to the genetic predisposition to systemic lupus erythematosus (SLE).

METHODS

First, intragenic markers for the bcl-2, IL-10, Fas-L, and CTLA-4 genes were characterized and their extent of polymorphism in normal populations was determined. The allelic distribution of these gene markers in a large Mexican American SLE cohort of 158 patients and 223 ethnically matched controls was determined using fluorescent-labeled primers and semiautomated genotyping.

RESULTS

The bcl-2, Fas-L, and IL-10 loci showed significantly different allelic distribution in SLE patients compared with controls, indicating an association between these genes and SLE. No association was found between SLE and the CTLA-4 gene. Further analysis revealed a synergistic effect between susceptibility alleles of the bcl-2 and IL-10 genes in determining disease susceptibility. Alone, the presence of each of these alleles was associated with a moderate increase in SLE risk, while the occurrence of these alleles together increased the odds of developing SLE by more than 40-fold.

CONCLUSION

The results suggest that individuals carrying specific genotypes of both bcl-2 and IL-10 are at significant risk of developing SLE.

Serum levels of interleukin-2 receptor and activity of rheumatic diseases characterized by immune system activation

Levels of interleukin-2 receptors (IL-2R), as measured by a double-antibody "sandwich" enzyme-linked immunosorbent assay technique, were markedly elevated in the serum of patients with systemic lupus erythematosus, rheumatoid arthritis, and bacterial endocarditis, but not in patients with acute gout. Serum levels of IL-2R correlated strongly with clinical and laboratory indicators of disease activity in patients with lupus and in those with rheumatoid arthritis. This relationship was confirmed by sequential determinations in individual patients. Serum IL-2R values correlated with disease activity better than did the Westergren erythrocyte sedimentation rate. Our findings indicate that serum levels of IL-2R may serve as a reliable serologic indicator of disease activity in inflammatory diseases characterized by immune system activation.

Human serum dopamine- -hydroxylase. Relationship to hypertension and sympathetic activity

Serum dopamine-β-hydroxylase activity varied from 3 to 581 units/ml in a group of 168 untreated adults (90 normals, 78 with borderline or overt hypertension). Levels did not correlate with blood pressure or age, but mean values were significantly lower in blacks than they were in whites. Subjects with exceptionally low levels of serum dopamine-β-hydroxylase activity showed normal cardiovascular function and normal β-hydroxylation of an administered synthetic substrate, hydroxyamphetamine. Pronounced blood pressure reduction by antihypertensive drugs did not change serum dopamine-β-hydroxylase activity, and intensive bicycle exercise produced only small and variable increases. Two subjects with severe sympathetic dysfunction, i.e., orthostatic hypotension, showed normal levels of dopamine-β-hydroxylase activity (89-123 units/ml). Serum dopamine-β-hydroxylase activity varied from 450 to 950 units/ml in five subjects with pheochromocytomas and decreased to one-tenth the preoperative level in one subject who underwent curative surgery. Therefore, serum dopamine-β-hydroxylase activity is not a satisfactory index of sympathetic function; moreover, activity levels do not correlate with prevailing blood pressure. Subjects with pheochromocytomas, however, may show increased serum levels of the enzyme, which demonstrates that such tumors can release dopamine-β-hydroxylase.

Comparison of techniques for measuring baroreflex sensitivity in man

Because discrepancies about baroreflex sensitivity in essential hypertension may have resulted from the use of different measurement techniques, we assessed the extent to which the results of different techniques agree in the same subjects. The eight techniques studied were the change in RR interval per unit change in systolic pressure during the Valsalva maneuver, upon release of the Valsalva maneuver, after injection of phenylephrine and after injection of nitroglycerin; the changes in RR interval and in systolic pressure per mm Hg externally applied neck suction; and the changes in RR interval and systolic pressure per mm Hg externally applied neck pressure. The average intercorrelation among these measures in 30 subjects was statistically significant (r = 0.36, p less than 0.01), but suggests that variance in one measure accounted for an average of about 13% of the variance in other measures. Standard deviations among subjects were often as large as the mean, indicating important interindividual variability as well. These findings demonstrate that baroreflex sensitivity varies widely among subjects and that different techniques for measuring baroreflex sensitivity probably measure different aspects of baroreflex function.

Potential roles of hypochlorous acid and N-chloroamines in collagen breakdown by phagocytic cells in synovitis

We have tested the effects of the neutrophil/macrophage products, hypochlorous acid (HOCl) and N-chloroamines, on the structural integrity and proteolytic susceptibility of collagen to determine if these agents could play a role in inflammatory joint destruction. Rates of HOCl reaction with collagen, and collagen gelation were monitored by spectrophotometric methods. Direct fragmentation, and degradation by collagenase were measured by the release of acid-soluble counts from 3H-collagen. Physiologically relevant concentrations of HOCl (5-50 microM) reacted rapidly and quantitatively at several sites in the collagen polypeptide chain, causing extensive protein fragmentation and preventing collagen gelation. In contrast, reaction with (5-50 microM) N-chloroalanine induced little direct collagen fragmentation. Oxidative damage by N-chloroamines was, however, evident because collagen displayed greatly increased proteolytic susceptibility following N-chloroamine treatment. Collagen degradation by collagenase increased as much as 3-fold after exposure to N-chloroamine treatment. Collagen degradation by collagenase increased as much as 3-fold after exposure to N-chloroalanine. N-chloroleucine caused a small increase in proteolytic susceptibility, but N-chlorotaurine had no effect. Collagen fragmentation by HOCl, inhibition of gelation by HOCl, and N-chloroalanine-induced proteolytic susceptibility, all increased with linear kinetics at oxidant concentrations of 5 microM to 1.0 mM. In synovitis, phagocytes expose collagen to HOCl, N-chloroamines, and collagenase. It is known that HOCl can activate neutrophil procollagenase. Based on our new findings, we propose a model of inflammatory joint destruction that also includes collagen fragmentation, and increased susceptibility of collagen to degradation by collagenase.(ABSTRACT TRUNCATED AT 250 WORDS)

Characterizaiton of two populations of human lymphocytes bearing easily detectable surface immunoglobulin

Two separate lymphocyte populations, each bearing easily detectable surface immunoglobulin, have been detected in human peripheral blood. The first, B cells, has surface determinants that are stable at 37degreeC, but are removed by pronase and regenerate in culture. The cells are nylon adherent and have a receptor for C3, and studies with unit gravity sedimentation indicate they are mostly small lymphocytes. B cells comprise 9.5% of the total lymphocytes, with the normal range from 3-16%. As many or more lymphocytes lack membrane-incorporated Ig determinants but have an Fc receptor that binds IgG1 and IgG3 in normal serum maximally at 4degreeC. This receptor for cytophilic IgG is removed by pronase but not by trypsin. The second population has been named L lymphocytes because of membrane-labile IgG determinants. L cells do not adhere to nylon, do not form rosettes with sheep erythrocytes sensitized with antibody and mouse complement, and are larger than small lymphocytes. These lymphocytes with cold-reactive Fc receptors for serum IgG do not form E-rosettes or respond to phytohemaggutinin. Since L cells do not have surface markers of T and B lymphocytes, it is likely that they comprise a separate population.

Correction of interleukin-2 production in patients with systemic lupus erythematosus by removal of spontaneously activated suppressor cells

Interleukin-2 (IL-2) production in vitro is depressed in systemic lupus erythematosus (SLE) patients. It is not known whether this abnormality is caused by a defect in the producer lymphocytes or by excessive suppression. We report that removal of OKT8 (Leu 2a)+ cells increased the IL-2 production by in vitro-stimulated lymphocytes to normal or above normal levels in 19 of 21 SLE patients. This increase was more apparent in those patients with clinically inactive disease and/or receiving less than 7.5 mg of prednisone. Removal of OKT8+ cells from normals did not significantly increase IL-2 activity. SLE, but not normal, OKT8+ cells decreased IL-2 production when added back to autologous OKT8-depleted cells. In some experiments, OKT8+ cells from normal donors also suppressed IL-2 production in SLE. This result suggests that the defect in IL-2 production is complex and may involve multiple cell interactions. Three lines of evidence suggest that the SLE OKT8+ cells actively inhibit the production of IL-2 rather than passively absorb this lymphokine: (a) only 3.2% of SLE lymphocytes expressed IL-2 receptors as detected with anti-Tac; (b) freshly prepared SLE lymphocytes did not absorb IL-2; and (c) cell-free supernatants from SLE OKT8+ cells inhibited IL-2 production, but not IL-2 activity. Double-labeling studies by flow cytometry revealed that 19.3% of SLE OKT8+ cells were also Ia-positive, and approximately 33% co-expressed the natural killer cell marker, HNK-1 (Leu 7). Removal of Leu 7+ cells also significantly elevated IL-2 production in SLE. These studies suggest that one or more circulating mononuclear cell subsets in SLE patients can suppress IL-2 production and that one subset may possibly belong to a non-T, non-B "third mononuclear population."

T lymphocyte subsets in systemic lupus erythematosus. Correlations with corticosteroid therapy and disease activity

The contribution of immune regulation to the etiology of systemic lupus erythematosus (SLE) is poorly understood. Using the monoclonal antibodies OKT4 and OKT8, we quantitated, by flow cytometry, T inducer/helper and T cytotoxic/suppressor cells in patients with SLE. Serologically active patients, who had clinical manifestations such as arthritis or rash and were not receiving prednisone, were characteristically lymphopenic due to a marked reduction in OKT4+ cells. Prednisone therapy produced the same phenomenon. Untreated patients, who were serologically inactive, demonstrated no abnormalities. These studies have thus revealed two presumably independent factors that can produce similar immunoregulatory aberrations.

CD8+ lymphocytes from patients with systemic lupus erythematosus sustain, rather than suppress, spontaneous polyclonal IgG production and synergize with CD4+ cells to support autoantibody synthesis

The cellular requirements for B cell hyperactivity in systemic lupus erythematosus (SLE) were studied. Removal of either CD8+ or CD4+ lymphocyte markedly decreased the spontaneous in vitro production of polyclonal IgG and of antigen-specific (anti-double-stranded DNA and antinucleoprotein) antibodies by SLE peripheral blood mononuclear cells (PBMC). The CD8+ lymphocytes that sustained IgG production were CD3+, HLA-DR+, and their activity was abrogated by preincubation with anti-HLA-DR monoclonal antibody. When both CD4+ and CD8+ cells were removed, the readdition of either subset partially restored polyclonal IgG production, but both cell subsets were required to reconstitute autoantibody production. Purified SLE B cell cultures, which generated only 15% of the IgG produced by unseparated PBMC, were fully reconstituted only by mixtures of CD4+ with CD8+ cells, and with CD8-, CD4-, CD16+ cells. At least part of the support for spontaneous IgG production can be attributed to endogenous interleukin-2 and interleukin-6.

The immunoregulatory effects of NK cells: the role of TGF-beta and implications for autoimmunity

The cytotoxic activities of natural killer (NK) cells--important in innate immunity--have received considerable attention, but NK cells also regulate T- and B-cell functions as well as hematopoiesis. Here, David Horwitz and colleagues focus on the capacity of NK cells to regulate antibody production positively and negatively, and in particular on the role of NK-cell transforming growth factor beta (TGF-beta) in downregulation of B-cell activity.

Effects of dietary potassium and race on urinary excretion of kallikrein and aldosterone in man

Urinary excretion of kallikrein by 16 normal and 8 hypertensive subjects was studied at three levels of dietary potassium: 85 meq/day for 5 days, 185 meq/day for 7 days, and 25 meq/day for 10 days. Excretion of kallikrein varied directly with potassium intake and paralleled excretion of aldosterone in both normotensive and hypertensive subjects. Mean levels of excretion of kallikrein at 85, 185, and 25 meq intake of potassium were 10.8, 19.1, and 5.8 esterase U/day (EU/day), respectively, for the normotensive subjects and 8.8, 13.9, and 6.1 EU/day for the hypertensive subjects. Mean levels of excretion of kallikrein were significantly higher in white that in black subjects among normals and hypertensives [13.0 vs. 5.9 EU/day for normals (P less than 0.05) and 13.7 vs. 4.0 EU/day for hypertensives (P less than 0.05) on the 85 meq/day diet]. The parallel changes in excretion of kallikrein and aldosterone support the hypothesis that changes in effective levels of aldosterone induce changes in the excretion of kallikrein. Because of racial differences in excretion of kallikrein, matched groups should be used for comparisons of the kallikrein system in disease states.

Rheumatoid vasculitis: effect of cyclophosphamide on the clinical course and levels of circulating immune complexes

A study of five patients with severe rheumatoid vasculitis treated with cyclophosphamide was undertaken to determine whether immune complexes were present in serum and if their levels correlated with disease activity and response to treatment. Circulating immune complexes were measured by various techniques including the Clq binding and Raji cell radioimmunoassays and determination of the presence of cryoglobulins. Elevated levels of circulating immune complexes, hypocomplementemia, and high titer rheumatoid factor were present during active vasculitis. Clinical and serologic remissions were induced in all patients on cyclophosphamide. In two patients in remission, a rise in rheumatoid factor titer and immune complex levels was associated with an exacerbation of vasculitis and resolved on increased cyclophosphamide dosage. The Clq binding assay and rheumatoid factor titer correlated best with clinical activity. Thus, circulating immune complexes appear to be involved in the immunopathogenesis of rheumatoid vasculitis, which can be successfully treated with cyclophosphamide.