Spesolimab, an Anti-Interleukin-36 Receptor Antibody, in Patients with Palmoplantar Pustulosis: Results of a Phase IIa, Multicenter, Double-Blind, Randomized, Placebo-Controlled Pilot Study

Introduction

Palmoplantar pustulosis (PPP) is a chronic, inflammatory skin disease, with high disease burden, that is often refractory to treatment. There is a high unmet clinical need for the treatment of patients with PPP. The objectives of this study were to evaluate the safety and efficacy of spesolimab, a novel anti-interleukin-36 receptor antibody, in patients with PPP.

Methods

This was a phase IIa, multicenter, double-blind, randomized, placebo-controlled pilot study comparing 900 mg spesolimab (n = 19), 300 mg spesolimab (n = 19), and placebo (n = 21) administered intravenously every 4 weeks until week 12 in patients with PPP. The primary efficacy endpoint was the achievement of Palmoplantar Pustulosis Area and Severity Index 50 (PPP ASI50) at week 16, defined as achieving an ≥ 50% decrease from baseline PPP ASI.

Results

At week 16, 31.6% of patients in both spesolimab dose groups achieved PPP ASI50 versus 23.8% receiving placebo (risk difference 0.078; 95% confidence interval –0.190, 0.338). Thus, the primary endpoint was not met. Spesolimab was well tolerated with no clinically relevant treatment-emergent safety signals observed.

Conclusions

PPP severity declined over time in all treatment groups after the start of treatment, with a faster decline in the spesolimab arms than in the placebo arm, indicating a potential treatment effect for spesolimab. Limitations to the study included a small sample size and lower overall disease severity than expected at baseline. It is possible that the primary efficacy endpoint may have coincided with natural disease resolution in some patients. Further effects of the efficacy of spesolimab in PPP are being explored in a phase IIb trial.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13555-021-00504-0.

Safety, pharmacokinetics and pharmacodynamics of BI 655064 in phase 1 clinical trials in healthy Chinese and Japanese subjects

Aims

To evaluate the safety, pharmacokinetics and pharmacodynamics of BI 655064 in healthy Chinese and Japanese subjects after administration of single doses of 80‐240 mg and multiple dosing of 240 mg once weekly over 4 weeks.

Methods

Two phase 1, double‐blind, placebo‐controlled studies were conducted (single‐rising doses of BI 655064 in Chinese/Japanese male subjects [n = 12 per BI 655064 dose group] or repeated 240 mg BI 655064 in Chinese male subjects [n = 9]). Plasma samples were collected to investigate BI 655064 pharmacokinetics, pharmacodynamics (CD40 receptor occupancy [RO]) and immunogenicity, along with the safety and tolerability of BI 655064.

Results

BI 655064 showed good overall tolerability following single‐dose administration of 80‐240 mg and repeated administration of 240 mg BI 655064 over 4 weeks. More Chinese subjects reported adverse events compared with Japanese subjects following single‐dose administration (59.4% vs 3.1%). BI 655064 exhibited nonlinear, saturable kinetics, with higher doses resulting in slower apparent clearance (0.514‐0.713 mL min⁻¹), and disproportionately higher total exposure (AUC_0‐inf; 5610‐7780 μg·h mL⁻¹) and maximum plasma concentration (15 700‐21 300 ng mL⁻¹) with 240 mg BI 655064. Ninety percent inhibition of CD40 RO was achieved with doses ≥120 mg, and a direct relationship between BI 655064 plasma concentration and inhibition of CD40 RO was observed. Most subjects had a positive treatment‐emergent antidrug antibody response.

Conclusions

BI 655064 pharmacokinetic and safety profiles in East Asian male subjects were consistent with those observed in a Western population. No adjustments in the BI 655064 dosing recommendations are warranted for future clinical trials.

Safety, pharmacokinetics and pharmacodynamics of BI 705564, a highly selective, covalent inhibitor of Bruton's tyrosine kinase, in Phase I clinical trials in healthy volunteers

Aims

To evaluate the safety, pharmacokinetics and pharmacodynamics of single‐ and multiple‐rising doses (MRDs) of BI 705564 and establish proof of mechanism.

Methods

BI 705564 was studied in 2 placebo‐controlled, Phase I clinical trials testing single‐rising doses (1–160 mg) and MRDs (1–80 mg) of BI 705564 over 14 days in healthy male volunteers. Blood samples were analysed for BI 705564 plasma concentration, Bruton's tyrosine kinase (BTK) target occupancy (TO) and CD69 expression in B cells stimulated ex vivo. A substudy was conducted in allergic, otherwise healthy, MRD participants. Safety was assessed in both studies.

Results

All doses of BI 705564 were well tolerated. Geometric mean BI 705564 plasma terminal half‐life ranged from 10.1 to 16.9 hours across tested doses, with no relevant accumulation after multiple dosing. Doses ≥20 mg resulted in ≥85% average TO that was maintained for ≥48 hours after single‐dose administration. Functional effects of BTK signalling were demonstrated by dose‐dependent inhibition of CD69 expression. In allergic participants, BI 705564 treatment showed a trend in wheal size reduction in a skin prick test and complete inhibition of basophil activation. Mild bleeding‐related adverse events were observed with BI 705564; bleeding time increased in 1/12 participants (8.3%) who received placebo vs 26/48 (54.2%) treated with BI 705564.

Conclusion

BI 705564 showed efficient target engagement through durable TO and inhibition of ex vivo B‐cell activation, and proof of mechanism through effects on allergic skin responses. Mild bleeding‐related adverse events were probably related to inhibition of platelet aggregation by BTK inhibition.

Effects of BI 655064, an antagonistic anti-CD40 antibody, on clinical and biomarker variables in patients with active rheumatoid arthritis: a randomised, double-blind, placebo-controlled, phase IIa study

OBJECTIVE

To evaluate the safety, efficacy and therapeutic mechanism of BI 655064, an antagonistic anti-CD40 monoclonal antibody, in patients with rheumatoid arthritis (RA) and an inadequate response to methotrexate (MTX-IR).

METHODS

In total, 67 patients were randomised to receive weekly subcutaneous doses of 120 mg BI 655064 (n=44) or placebo (n=23) for 12 weeks. The primary endpoint was the proportion of patients who achieved 20% improvement in American College of Rheumatology criteria (ACR20) at week 12. Safety was assessed in patients who received at least one dose of study drug.

RESULTS

At week 12, the primary endpoint was not met, with 68.2% of patients treated with BI 655064 achieving an ACR20 vs 45.5% with placebo (p=0.064); using Bayesian analysis, the posterior probability of seeing a difference greater than 35% was 42.9%. BI 655064 was associated with greater changes in CD40-CD40L pathway-related markers, including reductions in inflammatory and bone resorption markers (interleukin-6, matrix metalloproteinase-3, receptor activator of nuclear factor-κB ligand), concentration of autoantibodies (immunoglobulin [Ig]G rheumatoid factor [RF], IgM RF, IgA RF) and CD95+ activated B-cell subsets. No serious adverse events (AEs) related to BI 655064 treatment or thromboembolic events occurred; reported AEs were mainly of mild intensity.

CONCLUSION

Although blockade of the CD40-CD40L pathway with BI 655064 in MTX-IR patients with RA resulted in marked changes in clinical and biological parameters, including reductions in activated B-cells, autoantibody production and inflammatory and bone resorption markers, with a favourable safety profile, clinical efficacy was not demonstrated in this small phase IIa study.

TRIAL REGISTRATION NUMBER

NCT01751776.

Safety, Pharmacokinetics, and Pharmacodynamics of Multiple Rising Doses of BI 655064, an Antagonistic Anti-CD40 Antibody, in Healthy Subjects: A Potential Novel Treatment for Autoimmune Diseases

BI 655064 is a humanized antagonistic anti-cluster of differentiation (CD) 40 monoclonal antibody that selectively blocks the CD40-CD40L interaction. The CD40-CD40L pathway is a promising treatment target for autoimmune diseases such as rheumatoid arthritis, systemic lupus erythematosus, and lupus nephritis. The safety, tolerability, pharmacokinetics, and pharmacodynamics of repeated once-weekly BI 655064 subcutaneous dosing over 4 weeks were evaluated in a multiple-dose study in healthy subjects. Subjects (N = 40) were randomized 4:1 to four sequential BI 655064 dose groups (80, 120, 180, 240 mg) or to placebo. Safety and tolerability, plasma exposure, CD40 receptor occupancy, and CD40L-induced CD54 upregulation were assessed over 64 and 78 days for the 80- to 180-mg and 240-mg dose groups, respectively. BI 655064 exposure increased in a supraproportional manner, due to target-mediated drug clearance, for doses between 80 mg and 120 mg, but was near proportional for doses greater than 120 mg. Terminal half-life ranged between 6 and 8 days. Dose-dependent accumulation of BI 655064 supports the use of a loading dose in future clinical studies. Following 4 weeks of dosing, >90% CD40 receptor occupancy and inhibition of CD54 upregulation were observed at all dose levels, lasting for 17 days after the last dose. BI 655064 was generally well tolerated. There were no serious adverse events and the frequency and intensity of adverse events were similar for BI 655064 and placebo; no dose relationship or relevant signs of an acute immune reaction were observed. These findings support further investigation of BI 655064 as a potential treatment for autoimmune diseases.

Selective IL-23 Inhibition by Risankizumab Modulates the Molecular Profile in the Colon and Ileum of Patients With Active Crohn's Disease: Results From a Randomised Phase II Biopsy Sub-study

BACKGROUND AND AIMS

We aimed to investigate the underlying mechanism of action of risankizumab, a monoclonal antibody targeting the IL-23 p19 subunit, previously reported to induce clinical and endoscopic remission in a randomised phase II study in patients with active Crohn's disease.

METHODS

Ileum and colon biopsies obtained at screening and Week 12 from a subgroup of patients [n = 106] in the risankizumab phase II study were analysed by transcriptome-wide RNA-Seq profiling. Univariate associations were assessed using linear modelling.

RESULTS

By Week 12, risankizumab significantly decreased [p < 0.005] the expression of 1880 and 765 genes in the colon [false-discovery rate = 0.02] and ileum [false-discovery rate = 0.05], respectively. These genes were associated with the IL-23/IL-17 axis, Th1 pathway, innate immunity, and tissue turnover. Colonic transcriptomic profiles following risankizumab treatment reflected the transcriptomic changes observed in patients achieving endoscopic response and remission at Week 12 and were significantly different from placebo [p < 0.005]. The colonic transcriptomic profile, significantly modulated by risankizumab at Week 12, was indicative of suppression of pathways associated with epithelial biology. Furthermore, pathways associated with Crohn's disease modulated by risankizumab treatment included second messenger-mediated signalling, immune response, lymphocyte and leucocyte activation, lymphocyte differentiation and cell-cell adhesion.

CONCLUSIONS

Endoscopic remission and response observed with risankizumab in patients with active Crohn's disease was associated with significant transcriptomic changes in the colon, compared with placebo. Differentiated expression of genes associated with the IL-23/IL-17 axis was observed in the colon and ileum 12 weeks after risankizumab treatment.

Risankizumab, an IL-23 inhibitor, for ankylosing spondylitis: results of a randomised, double-blind, placebo-controlled, proof-of-concept, dose-finding phase 2 study

Objectives

To evaluate the efficacy and safety of risankizumab, a humanised monoclonal antibody targeting the p19 subunit of interleukin-23 (IL-23), in patients with active ankylosing spondylitis (AS).

Methods

A total of 159 patients with biological-naïve AS, with active disease (Bath Ankylosing Spondylitis Disease Activity Index score of ≥4), were randomised (1:1:1:1) to risankizumab (18 mg single dose, 90 mg or 180 mg at day 1 and weeks 8, 16 and 24) or placebo over a 24-week blinded period. The primary outcome was a 40% improvement in Assessment in Spondylo Arthritis International Society (ASAS40) at week 12. Safety was assessed in patients who received at least one dose of study drug.

Results

At week 12, ASAS40 response rates were 25.5%, 20.5% and 15.0% in the 18 mg, 90 mg and 180 mg risankizumab groups, respectively, compared with 17.5% in the placebo group. The estimated difference in proportion between the 180 mg risankizumab and placebo groups (primary endpoint) was –2.5% (95% CI –21.8 to 17.0; p=0.42). Rates of adverse events were similar in all treatment groups.

Conclusions

Treatment with risankizumab did not meet the study primary endpoint and showed no evidence of clinically meaningful improvements compared with placebo in patients with active AS, suggesting that IL-23 may not be a relevant driver of disease pathogenesis and symptoms in AS.

Trial registration number

NCT02047110; Pre-results.

Safety, pharmacokinetics and pharmacodynamics of single rising doses of BI 655064, an antagonistic anti-CD40 antibody in healthy subjects: a potential novel treatment for autoimmune diseases

PURPOSE

The CD40-CD40L pathway is a promising treatment target for autoimmune diseases such as rheumatoid arthritis, systemic lupus erythematosus and lupus nephritis. The safety, pharmacokinetics and pharmacodynamics of BI 655064, a novel humanised antagonistic anti-CD40 monoclonal antibody, were investigated in this first-in-human trial.

METHODS

Healthy male subjects (n = 72) were randomised 3:1, within each BI 655064 dose group, to single intravenous (IV; 0.2-120 mg) or subcutaneous (SC; 40-120 mg) doses of BI 655064 or placebo. Safety, plasma exposure, CD40 receptor occupancy and CD40L-induced CD54 upregulation were assessed over 12 weeks.

RESULTS

Adverse events (AEs) were reported in 43% of subjects (n = 31). Frequency and intensity of AEs were generally similar between BI 655064 and placebo and showed no dose relationship. The most frequent AEs were headache and nasopharyngitis. One mild rash and one local reaction occurred with SC BI 655064; two serious AEs were reported, both judged unrelated to BI 655064. Pharmacokinetic evaluation demonstrated a more than proportional increase in plasma exposure relative to BI 655064 dose, with a terminal half-life between 4 h and 4 days IV and approximately 5 days SC; doses ≥ 20 mg IV and 120 mg SC showed > 90% CD40 receptor occupancy and inhibition of CD54 upregulation, which lasted 7 days in the 120 mg IV and SC groups.

CONCLUSIONS

Single doses up to 120 mg BI 655064 IV and SC were well tolerated and showed a high potential to block the CD40-CD40L pathway, supporting further clinical development of BI 655064 in patients with autoimmune disease.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT01510782.

Induction therapy with the selective interleukin-23 inhibitor risankizumab in patients with moderate-to-severe Crohn's disease: a randomised, double-blind, placebo-controlled phase 2 study

BACKGROUND

The interleukin-23 pathway is implicated genetically and biologically in the pathogenesis of Crohn's disease. We aimed to assess the efficacy and safety of risankizumab (BI 655066, Boehringer Ingelheim, Ingelheim, Germany), a humanised monoclonal antibody targeting the p19 subunit of interleukin-23, in patients with moderately-to-severely active Crohn's disease.

METHODS

In this randomised, double-blind, placebo-controlled phase 2 study, we enrolled patients at 36 referral sites in North America, Europe, and southeast Asia. Eligible patients were aged 18-75 years, with a diagnosis of Crohn's disease for at least 3 months, assessed as moderate-to-severe Crohn's disease at screening, defined as a Crohn's Disease Activity Index (CDAI) of 220-450, with mucosal ulcers in the ileum or colon, or both, and a Crohn's Disease Endoscopic Index of Severity (CDEIS) of at least 7 (≥4 for patients with isolated ileitis) on ileocolonoscopy scored by a masked central reader. Patients were randomised 1:1:1 using an interactive response system to a double-blind investigational product, and stratified by previous exposure to TNF antagonists (yes vs no). Patients received intravenous 200 mg risankizumab, 600 mg risankizumab, or placebo, at weeks 0, 4, and 8. The primary outcome was clinical remission (CDAI <150) at week 12 (intention-to-treat population). Safety was assessed in patients who received at least one dose of study drug. This study is registered with ClinicalTrials.gov, number NCT02031276.

FINDINGS

Between March, 2014, and September, 2015, 213 patients were screened, and 121 patients randomised. At baseline, 113 patients (93%) had been previously treated with at least one tumour necrosis factor (TNF) antagonist (which had failed in 96 [79%]). At week 12, 25 (31%) of 82 risankizumab patients (pooled 41 patients in 200 mg and 41 patients in 600 mg arms) had clinical remission versus six (15%) of 39 placebo patients (difference vs placebo 15·0%, 95% CI 0·1 to 30·1; p=0·0489). Ten (24%) of 41 patients who received 200 mg risankizumab had clinical remission (9·0%, -8·3 to 26·2; p=0·31) and 15 (37%) of 41 who received the 600 mg dose (20·9%, 2·6 to 39·2; p=0·0252). 95 (79%) patients had adverse events (32 in the placebo group, 32 randomised to 200 mg risankizumab, 31 randomised to 600 mg risankizumab); 18 had severe adverse events (nine, six, three); 12 discontinued (six, five, one); 24 had serious adverse events (12, nine, three). The most common adverse event was nausea and most common serious adverse event was worsening of underlying Crohn's disease. No deaths occurred.

INTERPRETATION

In this short-term study, risankizumab was more effective than placebo for inducing clinical remission in patients with active Crohn's disease. Therefore, selective blockade of interleukin-23 via inhibition of p19 might be a viable therapeutic approach in Crohn's disease.

FUNDING

Boehringer Ingelheim.

Risankizumab versus Ustekinumab for Moderate-to-Severe Plaque Psoriasis

BACKGROUND

Interleukin-23 is thought to be critical to the pathogenesis of psoriasis. We compared risankizumab (BI 655066), a humanized IgG1 monoclonal antibody that inhibits interleukin-23 by specifically targeting the p19 subunit and thus prevents interleukin-23 signaling, and ustekinumab, an interleukin-12 and interleukin-23 inhibitor, in patients with moderate-to-severe plaque psoriasis.

METHODS

We randomly assigned a total of 166 patients to receive subcutaneous injections of risankizumab (a single 18-mg dose at week 0 or 90-mg or 180-mg doses at weeks 0, 4, and 16) or ustekinumab (45 or 90 mg, according to body weight, at weeks 0, 4, and 16). The primary end point was a 90% or greater reduction from baseline in the Psoriasis Area and Severity Index (PASI) score at week 12.

RESULTS

At week 12, the percentage of patients with a 90% or greater reduction in the PASI score was 77% (64 of 83 patients) for risankizumab (90-mg and 180-mg groups, pooled), as compared with 40% (16 of 40 patients) for ustekinumab (P<0.001); the percentage of patients with a 100% reduction in the PASI score was 45% in the pooled 90-mg and 180-mg risankizumab groups, as compared with 18% in the ustekinumab group. Efficacy was generally maintained up to 20 weeks after the final dose of 90 or 180 mg of risankizumab. In the 18-mg and 90-mg risankizumab groups and the ustekinumab group, 5 patients (12%), 6 patients (15%), and 3 patients (8%), respectively, had serious adverse events, including two basal-cell carcinomas and one major cardiovascular adverse event; there were no serious adverse events in the 180-mg risankizumab group.

CONCLUSIONS

In this phase 2 trial, selective blockade of interleukin-23 with risankizumab was associated with clinical responses superior to those associated with ustekinumab. This trial was not large enough or of long enough duration to draw conclusions about safety. (Funded by Boehringer Ingelheim; ClinicalTrials.gov number, NCT02054481 ).

Reactivity of dog sera to whole-cell or recombinant antigens of Borrelia burgdorferi by ELISA and immunoblot analysis

Enzyme-linked immunosorbent assays (ELISAs) with separate preparations of 10 purified recombinant antigens of Borrelia burgdorferi sensu stricto were used to test sera from 36 dogs not vaccinated with whole cells of this agent and from five dogs vaccinated with whole-cell B. burgdorferi bacteria. All dogs lived in tick-infested areas of Connecticut and south-eastern New York state, USA. The non-vaccinated dogs had limb or joint disorder, lameness and fever during the period 1984-1991 and had antibodies to B. burgdorferi, as determined by a polyvalent ELISA with whole-cell antigen. In re-analyses of sera for total immunoglobulins in ELISAs with recombinant antigens, reactions were most frequently recorded when outer-surface protein (Osp) F, protein (p)35, p37, p39 and p-41G (a flagellin component) were tested separately. Western immunoblots of a subset of 16 sera, positive by ELISA with whole-cell antigen and representing a range of antibody titres (640-40960), verified immune responses to these or other lysed whole-cell antigens. Sera from vaccinated dogs contained antibodies to OspA, OspB, p22, p37 and p41-G. Therefore, serological reactions to OspF, p35 and p39 were the most important indicators of natural exposure to B. burgdorferi. Serum reactivities to these recombinant antigens in ELISAs can be used to help identify possible natural infections of canine borreliosis in dogs not vaccinated with whole-cell B. burgdorferi and to provide information on the geographic distribution of this bacterium.

Serologic confirmation of Ehrlichia equi and Borrelia burgdorferi infections in horses from the northeastern United States

OBJECTIVE

To determine whether horses living in tick-infested areas of northeastern United States with clinical signs of borreliosis or granulocytic ehrlichiosis had detectable serum antibodies to both Borrelia burgdorferi and Ehrlichia equi.

DESIGN

Prospective study.

ANIMALS

Serum samples from 51 clinically normal horses, 14 horses with clinical signs of borreliosis, and 17 horses with clinical signs of granulocytic ehrlichiosis.

PROCEDURE

Serum B burgdorferi or E equi antibodies were measured by use of an ELISA, immunoblot analysis, or indirect fluorescent antibody (IFA) staining.

RESULTS

Of the 82 serum samples tested, 37 (45.1%) and 13 (15.9%) had detectable antibodies to B burgdorferi or E equi, respectively. Test results indicated that 12 horses had been exposed to both agents, 11 of these horses had granulocytic ehrlichiosis. The ELISA regularly detected antibodies to the following recombinant protein (p) antigens of B burgdorferi: p29, p37, p39, and p41-G. The use of immunoblot analysis confirmed ELISA results by indicating antibody reactivities to antigens of whole-cell B burgdorferi having molecular masses of predominantly 31, 34, 37, 39, 41, 58, and 93 kd.

CONCLUSIONS AND CLINICAL RELEVANCE

Horses living in areas where ticks (Ixodes scapularis) abound are sometimes exposed to multiple pathogens. Analyses for specific recombinant borrelial antibodies using an ELISA can help separate horses with borreliosis from those with granulocytic ehrlichiosis, even when antibodies to both etiologic agents are detected in serum samples. Analysis using immunoblots is sensitive, and along with ELISA or IFA procedures, is suitable for confirming a clinical diagnosis of each disease.

Serologic diagnosis of Lyme borreliosis by using enzyme-linked immunosorbent assays with recombinant antigens

Class-specific enzyme-linked immunosorbent assays (ELISAs) with purified recombinant antigens of Borrelia burgdorferi sensu stricto and Western blot analyses with whole cells of this spirochete were used to test human sera to determine which antigens were diagnostically important. In analyses for immunoglobulin M (IgM) antibodies, 14 (82%) of 17 serum samples from persons who had erythema migrans reacted positively by an ELISA with one or more recombinant antigens. There was frequent antibody reactivity to protein 41-G (p41-G), outer surface protein C (OspC), and OspF antigens. In an ELISA for IgG antibodies, 13 (87%) of 15 serum samples had antibodies to recombinant antigens; reactivity to p22, p39, p41-G, OspC, and OspF antigens was frequent. By both ELISAs, serum specimens positive for OspB, OspE, and p37 were uncommon. Analyses of sera obtained from persons who were suspected of having human granulocytic ehrlichiosis (HGE) but who lacked antibodies to ehrlichiae revealed IgM antibodies to all recombinant antigens of B. burgdorferi except OspB and IgG antibodies to all antigens except OspE. Immunoblotting of sera from the study group of individuals suspected of having HGE reaffirmed antibody reactivity to multiple antigens of B. burgdorferi. There was minor cross-reactivity when sera from healthy subjects or persons who had syphilis, oral infections, or rheumatoid arthritis were tested by ELISAs with p37, p41-G, OspB, OspC, OspE, and OspF antigens. Although the results of class-specific ELISAs with recombinant antigens were comparable to those recorded for assays with whole-cell antigen and for individuals with confirmed clinical diagnoses of Lyme borreliosis, immunoblotting is still advised as an adjunct procedure, particularly when there are low antibody titers by an ELISA.

The nuclear receptor PPAR gamma and immunoregulation: PPAR gamma mediates inhibition of helper T cell responses

The peroxisome proliferator-activated receptors (PPARs) are a family of transcription factors belonging to the nuclear receptor superfamily. Until recently, the genes regulated by PPARs were those believed to be predominantly associated with lipid metabolism. Recently, an immunomodulatory role for PPAR gamma has been described in cells critical to the innate immune system, the monocyte/macrophage. In addition, evidence for an antiinflammatory role of the PPAR gamma ligand, 15-deoxy-Delta 12,14-PGJ2 (15d-PGJ2) has been found. In the present studies, we demonstrate, for the first time, that murine helper T cell clones and freshly isolated splenocytes express PPAR gamma 1. The PPAR gamma expressed is of functional significance in that two ligands for PPAR gamma, 15d-PGJ2 and a thiazolidinedione, ciglitazone, mediate significant inhibition of proliferative responses of both the T cell clones and the freshly isolated splenocytes. This inhibition is mediated directly at the level of the T cell and not at the level of the macrophage/APC. Finally, we demonstrate that the two ligands for PPAR gamma mediate inhibition of IL-2 secretion by the T cell clones while not inhibiting IL-2-induced proliferation of such clones. The demonstration of the expression and function of PPAR gamma in T cells reveals a new level of immunoregulatory control for PPARs and significantly increases the role and importance of PPAR gamma in immunoregulation.

Human exposure to a granulocytic Ehrlichia and other tick-borne agents in Connecticut

Indirect fluorescent-antibody (IFA) staining methods with Ehrlichia equi (MRK or BDS strains) and Western blot analyses containing a human granulocytic ehrlichiosis (HGE) agent (NCH-1 strain) were used to confirm probable human cases of infection in Connecticut during 1995 and 1996. Also included were other tests for Ehrlichia chaffeensis, the agent of human monocytic ehrlichiosis (HME), Babesia microti, and Borrelia burgdorferi. Thirty-three (8.8%) of 375 patients who had fever accompanied by marked leukopenia or thrombocytopenia were serologically confirmed as having HGE. Western blot analyses of a subset of positive sera confirmed the results of the IFA staining methods for 15 (78.9%) of 19 seropositive specimens obtained from different persons. There was frequent detection of antibodies to a 44-kDa protein of the HGE agent. Serologic testing also revealed possible cases of Lyme borreliosis (n = 142), babesiosis (n = 41), and HME (n = 21). Forty-seven (26.1%) of 180 patients had antibodies to two or more tick-borne agents. Therefore, when one of these diseases is clinically suspected or diagnosed, clinicians should consider the possibility of other current or past tick-borne infections.

Serologic diagnosis of canine and equine borreliosis: use of recombinant antigens in enzyme-linked immunosorbent assays

Serum samples from dogs and equids suspected of having canine or equine borreliosis, respectively, were analyzed in polyvalent enzyme-linked immunosorbent assays (ELISAs) with whole-cell or recombinant antigens of Borrelia burgdorferi sensu stricto. Purified preparations of recombinant antigens included outer surface protein A (OspA), OspB, OspC, OspE, OspF, and p41-G (a fragment of flagellin). Of the 36 dog sera that reacted positively to whole-cell antigen, 32 (88.9%) contained antibodies to one or more recombinant antigens. Reactivities to OspF (88.9% positive) and p41-G (75% positive) were most prevalent. In analyses of 30 equid sera positive in an ELISA with whole cells, 24 (80%) contained antibodies to one or more recombinant antigens. Seropositivities in ELISAs with p41-G (50% positive) and OspF (46.7% positive) were more than twofold greater than in ELISAs with OspA, OspB, or OspC (10 to 20% positive). In parallel tests of eight canine and three equine sera, there was good agreement in results of Western blot (immunoblot) analyses and ELISAs. Although dog and equid sera with antibodies to whole-cell B. burgdorferi frequently reacted positively to one or more recombinant antigens, the inclusion of OspF and p41-G antigens in ELISAs was most useful in the serologic diagnosis of canine and equine borreliosis.

Use of recombinant antigens of Borrelia burgdorferi in serologic tests for diagnosis of lyme borreliosis

Recombinant antigens of outer surface proteins (Osps) OspA, OspB, OspC, OspE, and OspF of Borrelia burgdorferi sensu stricto and of p41-G, an antigenic region of flagellin of this spirochete, were tested with human sera in class-specific and polyvalent enzyme-linked immunosorbent assays (ELISAs). In analyses for immunoglobulin M (IgM) antibodies, 18 (85.7%) of 21 serum samples from persons who had been diagnosed as having Lyme borreliosis on the basis of the presence of erythema migrans reacted positively in ELISAs with one or more Osp antigens or the p41-G antigen. Eleven serum samples contained antibodies to OspC antigen, and of these, six also reacted to the p41-G antigen and to one or more of the other recombinant antigens. The remaining five serum samples reacted solely to OspC (n = 4) or to OspC plus OspA and OspE without reactivity to p41-G (n = 1). In analyses for IgG antibodies, seropositivity was comparable to that of IgM analyses and was marked by predominant reactivity to p41-G, OspC, and OspF. Similarly, all 21 serum samples were positive in polyvalent and class-specific ELISAs with whole-cell B. burgdorferi. Minor cross-reactivity was noted when sera from persons who had syphilis, periodontitis or other oral infections, or rheumatoid arthritis were tested with OspC, OspE, OspF, and p41-G. With relatively high degrees of specificity, ELISAs with recombinant antigens, particularly OspC and p41-G, can help to confirm B. burgdorferi infections.

Presentation of synthetic peptide antigen encoded by the MAGE-1 gene by granulocyte/macrophage-colony-stimulating-factor-cultured macrophages from HLA-A1 melanoma patients

The recent identification of the sequences of the peptides derived from a number of human melanoma-associated antigens has presented opportunities for developing a specific-peptide-based vaccine in this form of cancer. Since antigen-presenting cells (APC) play a crucial role in the induction of the T-cell-mediated immune response, we examined whether or not ex vivo cultured APC, bearing the appropriate MHC restricting elements, when pulsed with a relevant melanoma-specific cytotoxic-T-lymphocyte (CTL)-determined peptide, can present the peptide to the CTL. Here we show that a population of cells, derived from the monocyte/macrophage lineage from peripheral blood and grown in granulocyte/macrophage-colony-stimulating factor, exhibit many essential characteristics of "professional" APC (dendritic-type morphology with a proportion of the population, the B7 molecule, and high levels of MHC class I and class II molecules, CD11b and CD54 molecules) and are capable of efficiently presenting the nonapeptide, EADPTGHSY, encoded by the melanoma antigen MAGE-1 gene, to the MAGE-1-specific CTL clone, 82/30. These results suggest that this type of autologous ex vivo cultured population of professional APC, when pulsed with the relevant-CTL-determined peptide, can serve as a novel type of candidate vaccine for active specific immunization against HLA-A1-positive patients with melanoma expressing the MAGE-1 antigen.

Recombinant outer surface protein C ELISA for the diagnosis of early Lyme disease

To compare the sensitivity of a new ELISA for IgM antibodies to Borrelia burgdorferi that uses a recombinant outer surface protein C (rOspC) with those of a whole cell (WC) ELISA and an immunoblot assay for the diagnosis of early Lyme disease, serum specimens from 82 consecutive patients with physician-documented erythema migrans were analyzed. To compare the specificities of the three assays, serum specimens from 50 patients without a history of Lyme disease and from an area in which B. burgdorferi is not endemic were analyzed. The sensitivities of the WC ELISA, immunoblot assay, and IgM rOspC ELISA were 28%, 29%, and 46%, respectively, while the specificities were 100%, 100%, and 98%, respectively. The IgM rOspC ELISA is a convenient, readily automated, easily standardized serologic test that is significantly more sensitive for the diagnosis of early Lyme disease than either WC ELISA or immunoblot assay.

Increased collagen synthesis in skin fibroblasts from patients with primary hypertrophic osteoarthropathy. Evidence for trans-activational regulation of collagen transcription

OBJECTIVE

To investigate collagen synthesis in skin fibroblasts from patients with primary hypertrophic osteoarthropathy (HOA), a disorder characterized clinically by skin thickening.

METHODS

Collagenase-digestible protein, messenger RNA (mRNA) levels, and transcriptional activity of the alpha 1(I) procollagen gene were assessed in skin-derived fibroblast lines.

RESULTS

Compared with fibroblasts from uninvolved skin, fibroblasts from involved skin had elevated levels of collagen synthesis and alpha 1(I) procollagen mRNA, and increased transcriptional activity of the alpha 1(I) procollagen promoter.

CONCLUSION

Abnormalities of collagen synthesis in fibroblasts from patients with primary HOA can be accounted for, at least in part, by a trans-activated up-regulation of collagen transcription.

Use of recombinant OspC from Borrelia burgdorferi for serodiagnosis of early Lyme disease

Infection with Borrelia burgdorferi, the etiologic agent of Lyme disease, is associated with an early and dominant humoral response to the spirochete's 23-kDa outer surface protein C (OspC). We have cloned and expressed OspC as a fusion protein in Escherichia coli and have shown that patient serum samples react with it in an enzyme-linked immunosorbent assay (ELISA) (S. J. Padula, A. Sampieri, F. Dias, A. Szczepanski, and R. W. Ryan, Infect. Immun. 61:5097-5105, 1993). Now we have compared the detection of B. burgdorferi-specific immunoglobulin M antibodies in 74 individuals with culture-positive erythema migrans by a whole-cell ELISA, immunoblot, and the recombinant OspC (rOspC) ELISA. Seventy-six negative controls were also studied. With all of the tests, there was a statistically significant association between the duration of disease and the frequency of a positive result. With the rOspC ELISA, the predictive value of a positive test was 100% and the predictive value of a negative test was 74%. Similar results were obtained with the whole-cell ELISA and with the immunoblot using as the source of test antigen a strain of B. burgdorferi which expresses abundant levels of OspC. We conclude that the use of rOspC in an ELISA is a convenient, readily automated, and easily standardized test for the serodiagnosis of early Lyme disease.

Molecular characterization and expression of p23 (OspC) from a North American strain of Borrelia burgdorferi

We have found that sera from patients with early stages of Lyme disease contain predominant immunoglobulin M reactivity to a major 23-kDa protein (p23) from Borrelia burgdorferi 2591 isolated in Connecticut. To characterize this immunodominant antigen, we cloned and sequenced p23 and found it to be 83% identical by nucleotide sequence and 75% identical by amino acid sequenced to pC (recently renamed OspC), an abundantly expressed protein on the outer surface of PKo, a European strain of B. burgdorferi (B. Wilske, V. Preac-Mursic, S. Jauris, A. Hofmann, I. Pradel, E. Soutschek, E.Schwab, G. Will, and G. Wanner, Infect. Immun. 61:2182-2191, 1993). In addition, immunoelectron microscopy localized p23 to the outer membrane, confirming that p23 is the strain 2591 homolog of OspC. The North American strain B31, commonly used in serologic assays for Lyme disease, does not express OspC. Northern (RNA) blot analysis detected low levels of ospC mRNA in B31, and DNA sequencing of the ospC gene from B31 revealed a 54-bp deletion in the upstream regulatory region, possibly accounting for the low transcriptional activity of ospC. The ospC coding region from B31 was cloned and antibody-reactive OspC was expressed in Escherichia coli. An immunoglobulin M enzyme-linked immunosorbent assay using recombinant OspC as the target antigen shows promise for the serodiagnosis of early stages of Lyme disease.

Inhibition of interleukin-2 synthesis and interleukin-2 receptor alpha expression on T cells by a cell-free factor derived from a CD4+ regulatory T cell clone

We have shown that certain CD4+ T cell lines can function as suppressor cells in a cell culture system. In this context, the CD4+ T cells (AS-9) cloned from the peripheral blood lymphocytes (PBL) of a melanoma patient are capable of suppressing the induction of cytolytic response in autologous PBL in coculture. Here we show that a trypsin-sensitive cell-free culture supernatant factor from the AS-9 cells, AS-9 SF, interferes with IL-2 synthesis by T cells when they are stimulated. AS-9 SF also selectively blocks the expression of interleukin-2 receptor alpha (IL-2R alpha) on T cells during activation. Expression of transferrin receptors and the CD3 molecules is not down-regulated by this factor. The AS-9 SF consequently blocks proliferation of T cells when they are stimulated by lectin or activated through the T cell receptors. AS-9 SF suppresses the IL-2R alpha induction and the T cell proliferation at the induction phase only because it has no suppressive effect on preactivated T cells. Interleukin-2, IL-2R alpha, and beta messages are not down-regulated by the AS-9 SF and the suppressive effect of the AS-9 SF on IL-2R alpha expression and on T cell proliferation is not neutralized by the addition of exogenous recombinant IL-2. The factor does not appear to be IL-4, IL-10, or TGF-beta, three known cytokines possessing regulatory properties on T cell activation.

Analysis of cytolytic effector cell response in vitro against autologous human tumor cells genetically altered to synthesize interleukin-2

Recently, there has been a surge of interest in gene therapy in cancer particularly with cytokine transduced tumor cells as a novel form of tumor vaccine. In two autologous human tumor systems, using the tumor cells engineered to produce interleukin-2 by gene transduction techniques, we have examined whether or not such genetically altered cells are capable of inducing a tumor specific cytolytic T cell (CTL) response, in vitro, in co-culture with the respective autologous peripheral blood lymphocytes (PBL). We found that in neither system did co-cultures of the IL-2 producing tumor cells and the autologous PBL generate much cytolytic effector cell activity directed against the respective tumor cells, although these co-cultures did lead to the generation of substantial levels of natural killer (NK) cell activity when measured against the prototype NK sensitive target K562 line. More surprisingly, the levels of lymphokine activated killer cell responses against the respective autologous targets that could be generated in the PBL with exogenous IL-2 alone were compromised by the presence of the autologous tumor cells in the co-culture.

Adoptive transfer of activated human autologous macrophages results in regression of transplanted human melanoma cells in SCID mice

The potential anti-tumor activity of human macrophages, grown in macrophage colony stimulating factor (M-CSF), was examined in mice homozygous for the mutation severe combined immune deficiency (scid) bearing xenografts of autologous human melanoma. Injection of scid mice, bearing subcutaneous melanoma xenografts, with the cultured macrophages or with the macrophage culture supernatant, once or repeatedly, resulted in partial to complete regression of tumors. Since a large number of such macrophages (greater than 1 x 10(9)) could be grown in vitro for repeated injection, the scid-human chimera can serve as an in vivo model to examine the role of human macrophages in tumor immunity and to explore the potential of the in vitro cultured macrophages in the therapy of cancer.

Identification of encephalitogenic V beta-4-bearing T cells in SJL mice. Further evidence for the V region disease hypothesis?

Experimental allergic encephalomyelitis (EAE) is an autoimmune disease of the central nervous system mediated by T cells bearing TCR of restricted heterogeneity. Thus, in the murine PL strain, V beta-8.2 is used by 80% of the encephalitogenic T cells. This observation has led to the successful prevention and reversal of EAE by the in vivo use of mAb directed to these restricted gene products. In SJL mice, the V beta-17a gene product has been shown to be used by approximately 50% of encephalitogenic T cells subsequent to immunization with a myelin basic protein (MBP)-derived peptide. However, the other V beta genes used by encephalitogenic T cells in SJL EAE have remained uncharacterized. We now report, for the first time, the beta-chain-encoding DNA sequence of two encephalitogenic, MBP-reactive, SJL-derived T cell clones. These clones which are specific for H-2s and the carboxyl-terminus (amino acid 92-103) of MBP, use TCR encoded by V beta-4. In addition, we demonstrate that the transfer of EAE by a heterogenous SJL-derived encephalitogenic T cell line can be prevented using an anti-V beta-4 antibody in vivo. V beta-4 usage has been previously described in a H-2u/MBP amino-terminus-reactive encephalitogenic T cell. The present findings may thus further support the "V region-disease" hypothesis.

Identification of encephalitogenic V beta-4-bearing T cells in SJL mice. Further evidence for the V region disease hypothesis?

Experimental allergic encephalomyelitis (EAE) is an autoimmune disease of the central nervous system mediated by T cells bearing TCR of restricted heterogeneity. Thus, in the murine PL strain, V beta-8.2 is used by 80% of the encephalitogenic T cells. This observation has led to the successful prevention and reversal of EAE by the in vivo use of mAb directed to these restricted gene products. In SJL mice, the V beta-17a gene product has been shown to be used by approximately 50% of encephalitogenic T cells subsequent to immunization with a myelin basic protein (MBP)-derived peptide. However, the other V beta genes used by encephalitogenic T cells in SJL EAE have remained uncharacterized. We now report, for the first time, the beta-chain-encoding DNA sequence of two encephalitogenic, MBP-reactive, SJL-derived T cell clones. These clones which are specific for H-2s and the carboxyl-terminus (amino acid 92-103) of MBP, use TCR encoded by V beta-4. In addition, we demonstrate that the transfer of EAE by a heterogenous SJL-derived encephalitogenic T cell line can be prevented using an anti-V beta-4 antibody in vivo. V beta-4 usage has been previously described in a H-2u/MBP amino-terminus-reactive encephalitogenic T cell. The present findings may thus further support the "V region-disease" hypothesis.

An antibody to lymphotoxin and tumor necrosis factor prevents transfer of experimental allergic encephalomyelitis

Uncertainty regarding pathogenic mechanisms has been a major impediment to effective prevention and treatment for human neurologic diseases such as multiple sclerosis, tropical spastic paraparesis, and AIDS demyelinating disease. Here, we implicate lymphotoxin (LT) (tumor necrosis factor beta [TNF-beta]) and TNF-alpha in experimental allergic encephalomyelitis (EAE), a murine model of an autoimmune demyelinating disease. In this communication, we report that treatment of recipient mice with an antibody that neutralizes LT and TNF-alpha prevents transfer of clone-mediated EAE. LNC-8, a myelin basic protein-specific T cell line, produces high levels of LT and TNF-alpha after activation by concanavalin A, antibody to the CD-3 epsilon component of the T cell receptor, or myelin basic protein presented in the context of syngeneic spleen cells. LNC-8 cells transfer clinical signs of EAE. When LNC-8 recipient mice were also treated with TN3.19.12, a monoclonal antibody that neutralizes LT and TNF-alpha, the severity of the transferred EAE was reduced, while control antibodies did not alter the disease. The effect of anti-LT/TNF-alpha treatment was long lived and has been sustained for 5 mo. These findings suggest that LT and TNF-alpha and the T cells that produce them play an important role in EAE.

Effects of H-7 are not exclusively mediated through protein kinase C or the cyclic nucleotide-dependent kinases

Culturing murine T cell tumor lines in the presence of the protein kinase inhibitor H-7 for 4 days led to their dependence on H-7 for maximal constitutive proliferation. Withdrawal of H-7 from H-7-conditioned cells led to inhibition of proliferation and cell death. The mechanism underlying this H-7 dependence does not appear to be related to clonal selection or to effects on protein kinase C or the cyclic nucleotide-dependent kinases. This suggests that all the effects of the widely used H-7 may not be completely understood, and that H-7 may be useful in the dissection of the complex patterns of growth regulation in T cell malignancies.

Subtypes of helper cells. Non-inflammatory type 1 helper T cells

Class II MHC-restricted T cells recently have been characterized as being either type 1 (Th1) or type 2 (Th2) based on their ability to both secrete different lymphokines and perform different functions. Characterization of these subtypes to date have indicated that Th1 cells secrete IL-2, IFN-gamma, lymphotoxin, and IL-3, whereas Th2 cells secrete IL-4, IL-5, and IL-3. Functionally, Th1 cells mediated cytotoxicity and delayed-type hypersensitivity, and have been termed "inflammatory cells," whereas Th2 cells mediate helper function for Ig secretion and have been termed, "regulatory cells." We now present evidence that not all Th1 clones are inflammatory and capable of mediating cutaneous delayed-type hypersensitivity. We have generated a number of myelin basic protein-specific Th1 clones that do not mediate swelling when injected together with myelin basic protein directly into the footpads of syngeneic mice. These results suggest that Th1 cells can be further subdivided based on their ability to mediate delayed-type hypersensitivity, and that the Th1/Th2 characterization of Th cells may be insufficient to adequately characterize all functional subtypes of class II MHC-restricted T cells.

Subtypes of helper cells. Non-inflammatory type 1 helper T cells

Class II MHC-restricted T cells recently have been characterized as being either type 1 (Th1) or type 2 (Th2) based on their ability to both secrete different lymphokines and perform different functions. Characterization of these subtypes to date have indicated that Th1 cells secrete IL-2, IFN-gamma, lymphotoxin, and IL-3, whereas Th2 cells secrete IL-4, IL-5, and IL-3. Functionally, Th1 cells mediated cytotoxicity and delayed-type hypersensitivity, and have been termed "inflammatory cells," whereas Th2 cells mediate helper function for Ig secretion and have been termed, "regulatory cells." We now present evidence that not all Th1 clones are inflammatory and capable of mediating cutaneous delayed-type hypersensitivity. We have generated a number of myelin basic protein-specific Th1 clones that do not mediate swelling when injected together with myelin basic protein directly into the footpads of syngeneic mice. These results suggest that Th1 cells can be further subdivided based on their ability to mediate delayed-type hypersensitivity, and that the Th1/Th2 characterization of Th cells may be insufficient to adequately characterize all functional subtypes of class II MHC-restricted T cells.

T cell receptor beta chain gene rearrangement shared by murine T cell lines derived from a site of autoimmune inflammation

Advances in our understanding of the structure and molecular biology of the T lymphocyte antigen-receptor have now made it feasible to study human autoimmune diseases using new approaches. One such approach involves cloning of T cells from sites of autoimmune pathology followed by identification of putative disease-related T cell oligoclonality at the level of the T cell receptor gene rearrangements. We have now tested the feasibility of this approach in an animal model of autoimmunity, murine experimental allergic encephalomyelitis (EAE). Spinal cord-derived, self (murine) myelin basic protein (MBP)-reactive T cell lines and sublines were analyzed at the level of their receptor beta chain rearrangements using Southern blots. We now report that the MBP-reactive T cell lines and sublines derived from the spinal cords of four of five SJL/J mice with EAE share a 14.5-kb rearranged T cell receptor beta 1 band on Southern blots. A spinal cord-derived T cell line that was reactive to purified protein derivative of tuberculin (PPD), several lymph node-derived ovalbumin- and PPD-reactive T cell lines, as well as one MBP-reactive spinal cord-derived T cell line did not share this 14.5-kb rearranged beta 1 band. These results suggest that analysis of the antigen receptors used by T cells cloned from sites of inflammation may be a useful initial approach for identifying pathogenetically relevant T cells in the study of certain human autoimmune diseases.

Allogeneic fibroblasts and endothelial cells support mitogen but not antigen responses of tetanus-responsive T-cell lines

Recent studies suggest a role for endothelial cells (EC) and fibroblasts (FB) in performing certain accessory functions of monocytes in immune responses. We examined the ability of allogeneic adherent cells (AC), umbilical vein EC, and foreskin FB to support antigen and mitogen responses of tetanus toxoid-responsive human T-cell lines (TCTet). Syngeneic AC supported antigen and mitogen (phytohemagglutinin and pokeweed mitogen, PHA and PWM) responses of TCTet. Allogeneic AC, EC, and FB supported mitogen but not antigen responses of TCTet, in a dose-dependent manner. PHA-activated mononuclear cell supernates or EC or FB supernates could not replace accessory cells in mitogen responses. We provide further evidence that EC and FB can function as fully competent accessory cells, a function that may be of significance in in vivo initiation of immune responses.

Cell-mediated immunity in rheumatic disease

Rheumatoid arthritis, systemic lupus erythematosus, and systemic sclerosis are the three most common systemic rheumatic diseases in which disordered immune function is thought to play a pathogenetic role. Each disease has different and characteristic abnormalities of the cellular immune system. In rheumatoid arthritis the identified abnormalities of immunoregulation are largely limited to specific antigens: Epstein-Barr virus and collagen. Systemic lupus erythematosus is characterized by exuberant B-cell activity with exaggerated humoral response, a diversity of autoantibodies, non-antigen-specific loss of suppressor cell function, and general suppression of cell-mediated immunity. In systemic sclerosis systemic defects of cellular and humoral immune function are mild, but the release of lymphokines and monokines at sites of inflammatory lesions is thought to be important in the pathogenesis of the disease. Similar immune cell-connetive tissue cell interactions are probably important in the propagation of rheumatoid synovitis. Thus, despite the many shared clinical and serologic features of these diseases as well as the presence of many patients who have clinically overlapping features of more than one of these entities, the immune defects and the immunopathogenesis of these disorders appear to be distinct.

Maintenance of antigen specificity by human interleukin-2-dependent T cell lines. Use of antigen-presenting cells and OKT3 antibody in the absence of antigen

The in vitro growth of T cells obtained from localized anatomic sites of pathology may offer a new approach to the investigation of certain human autoimmune diseases. However, if interleukin-2-dependent T cell cloning is to be useful in helping to elucidate putative pathogenetic antigens in these diseases, the expansion of the small number of T cells obtainable from localized anatomic sites of pathology will often have to be accomplished in the absence of these, as yet undetermined, antigens. At present, it is a generally held belief that antigen-responsive, interleukin-2-dependent T cell lines and clones will lose antigen responsiveness if propagated in the absence of specific antigen. Thus, the use of T cell cloning might be viewed as being of limited usefulness in the investigation of certain human autoimmune diseases. In this report we demonstrate that, when propagated in the absence of antigen, human tetanus toxoid-specific, interleukin-2-dependent T cell lines will indeed lose antigen reactivity. However, if propagated in the absence of antigen but in the presence of antigen-presenting cells, the tetanus toxoid reactivity of a subset of such lines can be maintained. Moreover, the propagation with OKT3 antibody, in addition to antigen-presenting cells, may be even more effective in maintaining antigen reactivity. These results may suggest a new approach to the use of T cell cloning technology in the investigation of certain autoimmune diseases.