Transforming growth factor beta enhances the expression of CD154 (CD40L) and production of tumor necrosis factor alpha by human T lymphocytes.

Activation of lymphocytes in the presence of transforming growth factor beta (TGFbeta) can impair or enhance their functional activity. We have found that TGFbeta is important in the generation of lymphocytes, which are capable of suppressing antibody production. To better understand how this cytokine affects lymphocyte activity, we looked at the expression of early activation events of T cells stimulated in the presence or absence of TGFbeta. The results show that TGFbeta enhances the expression of CD154 (CD40L), TNFR2 and the production of TNFalpha. These findings clarify the co-stimulatory effects of TGFbeta that enhance T lymphocyte activation.

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.

Role of NK cells and TGF-beta in the regulation of T-cell-dependent antibody production in health and autoimmune disease.

Natural killer (NK) cells are a third lymphocyte population especially important in innate immunity. NK cells may also have an important role in the regulation of acquired immunity. These lymphocytes spontaneously produce large amounts of both active and latent transforming growth factor-beta (TGF-beta). NK-cell-derived TGF-beta1 enabled activated CD8(+) T cells to inhibit antibody production by blocking the induction of this response. Production of lymphocyte-derived TGF-beta is decreased in systemic lupus erythematosus. Insufficient levels of this cytokine in SLE and other autoimmune diseases may contribute to defective T regulatory cell function characteristic of this and other autoimmune diseases. NK cells are found in mucosal tissues and the TGF-beta spontaneously released by these cells could contribute to the usual tolerogenic response of T cells to antigens presented at these sites. Thus, in addition to its well known immunosuppressive effects, TGF-beta could have an equally important role in the generation of regulatory T cells.

Impaired cytotoxic T lymphocyte activity in systemic lupus erythematosus following in vitro polyclonal T cell stimulation: a contributory role for non-T cells.

To determine whether non-T cells contribute to impaired generation of nonrestricted cytotoxic T lymphocyte (CTL) activity in human SLE, peripheral blood mononuclear cells (PBMC) and sort-purified T cells from normal subjects and SLE patients were stimulated with anti-CD3 mAb, maintained in IL2, and assayed for cytolytic activity against 51Cr-labeled Daudi target cells. In addition, T cell and non-T cell fractions were isolated from nine pairs of monozygotic (MZ) twins discordant for SLE, reconstituted in a criss-cross pattern, and stimulated and assayed for cytolytic activity. Cytolytic responses were significantly lower in SLE PBMC cultures than in normal PBMC cultures. Addition of SLE serum to normal PBMC cultures did not inhibit generation of normal cytolytic responses, and neither 'resting' SLE PBMC prior to stimulation nor addition of neutralizing anti-IL10 mAb or costimulating anti-CD28 mAb restored generation of SLE cytolytic responses to normal. Nevertheless, despite the significantly greater cytolytic responses in normal PBMC cultures than in SLE PBMC cultures, cytolytic responses in normal purified T cell cultures were only modestly and insignificantly greater than those in SLE purified T cell cultures. Moreover, substitution of 'healthy' non-T cells for SLE non-T cells in four of the nine MZ twin-pairs appreciably enhanced cytolytic responses, and substitution of SLE non-T cells for 'healthy' non-T cells in five of the seven twin-pairs tested appreciably diminished cytolytic responses. Taken together, these results indicate that, in addition to any inherent SLE T cell abnormalities, impaired function of SLE non-T cells contributes to impaired generation of nonrestricted CTL activity.

The relationship between defects in lymphocyte production of transforming growth factor-beta1 in systemic lupus erythematosus and disease activity or severity.

Transforming growth factor beta (TGF-beta) comprises of a family of proteins with pleiotropic signaling properties and potent immunoregulatory effects. In SLE we recently reported that lymphocyte production of the total and active forms of TGF-beta1 was decreased. Here we asked whether these defects correlate with disease activity and/or severity. TGF-beta1 production by blood lymphocytes from 17 prospectively studied SLE patients was compared with 10 rheumatoid arthritis (RA) patients and 23 matched healthy controls. The RA levels of active TGF-beta1 were lower than controls, but were not deceased to the extent found in SLE. Levels of constitutive and anti-CD2 stimulated active TGF-beta1 detected in picomolar amounts were markedly reduced in six untreated patients hospitalized with recent onset, very active and severe SLE and similarly reduced in 11 patients with treated, less active disease. By contrast, decreased production of total TGF-beta1 inversely correlated with disease activity. These studies suggest, therefore, that although impaired lymphocyte secretion of the latent precursor of TGF-beta1 may result as a consequence of disease activity, a decreased capacity to convert the precursor molecule to its active form may pre-date disease onset. Insufficient exposure of T cells to picomolar concentrations of TGF-beta1 at the time they are activated can result in impaired down-regulation of Ig synthesis. Therefore, decreased lymphocyte production of active TGF-beta1 in SLE could be an immunologic defect which contributes to the B cell hyperactivity characteristic of this disease.

Cytokine-mediated down-regulation of B cell activity in SLE: effects of interleukin-2 and transforming growth factor-beta.

We have recently reported that transforming growth factor-beta (TGF-beta) co-stimulates interleukin-2 (IL-2) activated CD8+ T cells to down-regulate antibody production. In SLE, lymphocyte production of both IL-2 and TGF-beta is decreased. Here we report that a brief treatment of PBMC from SLE patients with IL-2 and TGF-beta can result in marked inhibition of spontaneous polyclonal IgG and autoantibody production. Peripheral blood mononuclear cells (PBMC) from 12 patients with active SLE were exposed to IL-2 with or without TGF-beta for three days, washed and cultured for seven more days. The mean decrease in IgG secretion was 79%. The strongest inhibitory effect was observed in cases with the most marked B cell hyperactivity. Spontaneous production of anti-nucleoprotein (NP) antibodies was observed in four cases and cytokine treatment of PBMC decreased autoantibody production by 50-96%. IL-2 inhibited Ig production by either TGF-beta-dependent or independent mechanisms in individual patients. In a study of anti-CD2 stimulated IgG production in a patient with active SLE, we documented that IL-2 and TGF-beta reversed the enhancing effects of CD8+ T cells on IgG production and induced suppressive activity instead. These results raise the possibility that cytokine-mediated down-regulation of B cell hyperactivity in SLE may have therapeutic potential.

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.

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.

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.

Generation of an inhibitory circuit involving CD8+ T cells, IL-2, and NK cell-derived TGF-beta: contrasting effects of anti-CD2 and anti-CD3.

Although the phenomenon of immunosuppression is well established, the mechanisms involved in the generation of lymphocytes with down-regulatory activity are poorly understood. Unlike anti-CD3 antibodies, mitogenic combinations of anti-CD2 antibodies do not stimulate human PBL to produce IgM or IgG. In determining the reason for this difference, we have found that anti-CD2 triggers an inhibitory circuit facilitated by TGF-beta provided by NK cells. Stimulation of PBL with anti-CD2, but not anti-CD3, generated substantial amounts of active TGF-beta. NK cells were found to be a significant source of TGF-beta and were the only lymphocyte population that constitutively produced this cytokine. Anti-CD2 enhanced the production of active TGF-beta by purified NK cells. TGF-beta. After the removal of NK cells or the addition of anti-TGF-beta, anti-CD2 could stimulate Ig production. Anti-TGF-beta had to be added within the first 24 h for a maximal effect. Moreover, a short, overnight exposure of CD8+ T cells to TGF-beta could prime them for suppressor activity provided that IL-2 was also present. Thus, the presence of active TGF-beta coincident with CD8+ T cell activation can condition these cells to mediate down-regulatory activity, and NK cells can serve as the source of this cytokine.

Decreased production of TGF-beta by lymphocytes from patients with systemic lupus erythematosus.

TGF-beta has marked inhibitory effects on the immune system but also serves as a costimulatory factor in the development of T cells with down-regulatory activities. This cytokine is secreted as a latent complex and converted extracellularly to its active form. We have recently learned that anti-CD2 is a potent inducer of lymphocyte-derived TGF-beta and that NK cells are the predominant source. The objective of this study was to compare levels of constitutive, anti-CD2-induced and cytokine-regulated TGF-beta produced by blood lymphocytes from patients with systemic lupus erythematosus (SLE) in comparison with healthy controls. Using a highly sensitive and specific bioassay to assess TGF-beta, we report that unstimulated PBL from SLE patients, especially the NK cell subset, produced decreased levels of active TGF-beta. In response to anti-CD2, concentrations of active and total TGF-beta were also decreased in SLE. After learning that IL-2 and TNF-alpha enhance lymphocyte production of active TGF-beta, we found that the addition of these cytokines was unable to increase active TGF-beta to normal concentrations. Although we observed that IL-10 inhibited the production of active TGF-beta, antagonism of this cytokine was unable to completely correct the defect. In two SLE patients with B cell hyperactivity, spontaneous IgG production was almost abolished by the combination of TGF-beta and IL-2. Therefore, decreased production of each of these cytokines in SLE could be important in the perpetuation of B cell hyperactivity.

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.

Decreased T cell response to anti-CD2 in systemic lupus erythematosus and reversal by anti-CD28: evidence for impaired T cell-accessory cell interaction.

OBJECTIVE: To assess the ability of T cells from patients with systemic lupus erythematosus (SLE) to respond to a mitogenic combination of anti-CD2 monoclonal antibodies (MAb), and to learn the molecular basis of the documented defect. METHODS: Peripheral blood mononuclear cell (PBMC) populations from individuals with SLE and paired controls were stimulated in vitro with anti-CD2, and the proliferative response was compared with that evoked by stimulation with phytohemagglutinin (PHA) and anti-CD3. Surface markers on lymphocyte populations were assessed by flow cytometry after staining with specific MAb. RESULTS: The proliferative response to anti-CD2 was decreased to a greater extent than was the response to anti-CD3 or PHA in SLE patients. This defect was found in approximately one-half of the patients examined, was not associated with disease activity, and was maintained upon repeated testing. Since either monocytes or resting B cells can serve as accessory cells for T cells following activation by anti-CD2, we examined the T cell response after depletion of adherent cells. In approximately two-thirds of the individuals with a decreased response, depletion of monocytes or substitution of monocytes with allogeneic, resting B cells from normal donors corrected the defect. The addition to PBMC of anti-CD28, but not of a neutralizing antibody to interleukin-10, largely reversed the anti-CD2 proliferative defect. Significantly fewer CD8+ T cells expressed CD28 in SLE, and this defect was also documented, to a lesser extent, in CD4+ cells. CONCLUSION: This study provides evidence that some functional T cell defects in SLE may be due, at least in part, to decreased CD28-mediated costimulatory activity following the interaction of T cells with conventional accessory cells.

Impaired recovery and cytolytic function of CD56+ T and non-T cells in systemic lupus erythematosus following in vitro polyclonal T cell stimulation. Studies in unselected patients and monozygotic disease-discordant twins.

OBJECTIVE: To determine whether there is impaired generation and cytolytic function of CD56+ T cells and non-T cells in human systemic lupus erythematosus (SLE). METHODS: Peripheral blood mononuclear cells (PBMC) were obtained from 73 patients with SLE, 39 normal controls, and 9 pairs of monozygotic (MZ) twins discordant for SLE. PBMC were stimulated with anti-CD3 monoclonal antibody, maintained in interleukin-2, and assayed for percentages of total CD56+ cells and CD56+ T cells by flow cytometry, and for cytolytic activity against 51Cr-labeled Daudi target cells. RESULTS: Despite normal total cell expansion, the percentages of recovered CD56+ T cells and total CD56+ cells were 1.6-fold and 1.8-fold lower, respectively, in patients with SLE compared with normal controls (P = 0.011 and P < 0.001, respectively). Cytolytic activities of isolated total CD56+ cells and CD56+ T cells and were also reduced in patients with SLE compared with normal controls (P = 0.033). These defects associated with SLE were independent of disease activity and immunosuppressive medications, and they reflected impaired maturation of cytolytic effector cells rather than a deficiency in precursor cell number. In MZ twins discordant for SLE, recovered percentages of CD56+ cells and cytolytic responses were very low in 4 of 8 and 6 of 9 co-twins with SLE, respectively. Cellmixing experiments with the PBMC of the MZ twins demonstrated that the E+ cell fractions (containing all T cells and CD56+ non-T cells) from the co-twins with SLE had decreased ability to generate cytolytic activity compared with the corresponding E+ cell fractions from the healthy co-twins. However, recovered percentages of CD56+ cells and non-T cells and cytolytic responses were also depressed in 4 of 8 and 4 of 9 healthy co-twins, respectively. CONCLUSION: Impaired CD56+ T cell and non-T cell responses are a feature of SLE and may antedate the onset of clinical disease.

Activated human NK cells can stimulate resting B cells to secrete immunoglobulin.

In addition to their cytotoxic function, NK cells can either suppress or enhance Ab production. Upon activation, NK cells generally amplify Ig secretion by activated B cells. We now report that activated NK cells prepared from human peripheral blood can induce resting B cells to produce IgM and IgG. This was demonstrated by adding IL-2 or pokeweed mitogen to purified NK cells and B cells. The addition of IL-2-activated NK cells to B cells also had this effect. The responding B cells did not require activation. Moreover, following fractionation of B cells on Percoll gradients, responsive B cells were found in the high density as well as the low density fractions. The NK cell stimulatory effect was a two-step process. The first step induced B cells to respond to soluble mediators and was mediated by unstimulated NK cells, but not CD4 nor CD8 T cells. Physical contact between NK cells and B cells was required, and mAbs to CD11a and CD54 blocked this interaction. The second step was the production of as yet unidentified cytokine(s) by activated NK cells. These direct T cell-independent stimulatory effects of NK cells on B cells may be important in autoimmune and other chronic inflammatory diseases in which the suppressive effects of NK cells may be blocked.

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.

Cytokine gene profile in circulating blood mononuclear cells from patients with systemic lupus erythematosus: increased interleukin-2 but not interleukin-4 mRNA.

Cytokines are important in developmental and effector pathways of lymphocyte function. Our objective was to elucidate the profile of cytokines produced by circulating mononuclear cells from patients with systemic lupus erythematosus as estimated from studies of cytokine-gene activation. cDNA prepared by reverse transcription of lymphocyte mRNA was amplified using the polymerase chain reaction and normalized on the basis of beta-actin gene expression. Of 10 cytokines investigated in 16 individuals, differences between SLE and controls were found in only three. IL-2 transcripts were detected in four of six cases of subjects hospitalized for active SLE, but in only one of seven healthy controls, and none of three cases with pulmonary tuberculosis. By contrast, IL-4 transcripts were decreased compared with healthy controls and patients with tuberculosis. Also, TGF beta transcripts appeared to be decreased in SLE. All individuals studied regularly demonstrated high levels of transcripts for IL-1 beta, IL-6 and TNF alpha and transcripts for IFN gamma, TNF beta, IL-5 and IL-10 were variably expressed. In a second group of six SLE patients with less active disease, there was also a decrease in IL-4 expression compared with six healthy controls. Moreover, assays performed on sera from patients with active SLE revealed that IL-4 levels were not increased. Although in mice this cytokine has a well documented role in supporting antibody production, this study provides no evidence that IL-4 is involved in the B cell hyperactivity characteristic of human SLE.

Enhancing effects of interleukin 2-treated peripheral blood mononuclear cells on subsequent B cell differentiation.

Despite an extensive literature dealing with IL2-induced cytolytic activity, noncytotoxicity-related effects of IL2 on peripheral blood mononuclear cells (PBMC) or T cell function have received less attention. We have focused on the effects of irradiated, IL2-activated PBMC (PBMC*rIL2) on anti-CD3- and formalin-fixed heat-killed Staphylococcus aureus-induced polyclonal B cell differentiation in secondary cultures. PBMC*rIL2 act directly on B cells and cross major histocompatibility complex barriers to augment polyclonal B cell differentiation as measured by plaque-forming cell (PFC) generation. These effects are preferentially mediated by T (both CD4+ and CD8+) cells, and physical contact between effector PBMC*rIL2 and target B cells is not absolutely required for enhanced PFC generation. PBMC*rIL2 must be present for the initial 24 hr of the secondary cultures, indicating that some soluble B cell differentiation factor rapidly released by PBMC*rIL2 mediates the PFC-enhancing effect. Of IL2, IL4, IL5, IL6, IL10, IFN-gamma, and TNF-alpha, only IFN-gamma mRNA is appreciably and reproducibly increased in irradiated, IL2-activated T cells (T cells*rIL2). Nevertheless, exogenous rIFN-gamma cannot mimic and anti-IFN antibodies cannot block the PFC-enhancing effects of T cells*rIL2, indicating that some unidentified soluble factor(s) apart from or in addition to IFN-gamma is involved. IL2-induced effects on T cell noncytolytic function may help explain certain observed immune anomalies in IL2-treated patients, and a better understanding of the IL2-induced effects on T cell noncytolytic function may have ramifications for autoimmune diseases such as SLE.

Inhibition of collagenase activity by N-chlorotaurine, a product of activated neutrophils.

OBJECTIVE: To study the effects of N-chlorotaurine on collagenase activity, as a model of the effects of neutrophil activation in inflammatory arthritis. METHODS: Collagen degradation by collagenase was measured by the release of acid-soluble counts from 3H-collagen. RESULTS: N-chlorotaurine inhibited the degradation of collagen by bacterial collagenase. This result is explained by a direct inhibition/inactivation of collagenase, since N-chlorotaurine had no effect on the proteolytic susceptibility of collagen itself. The effect appears to be specific to N-chlorotaurine since N-chloroalanine, N-chloroleucine, and HOCl/OCl- failed to inhibit collagenase; in fact, N-chloroalanine and N-chloroleucine actually increased the proteolytic susceptibility of collagen. CONCLUSION: N-chlorotaurine may minimize damage to cartilaginous joint structures in inflammatory arthritis by inhibiting/inactivating collagenase.