[Influence of underlying disease and immunosuppression on the immunocompetence in inflammatory rheumatic diseases]

Patients with inflammatory rheumatic diseases have a higher risk of infections in comparison to the general population. For this patient group, in addition to cardiovascular diseases, infections play an important role with respect to morbidity and mortality. Even if it is difficult to make concrete statements with respect to individual diseases, it can be assumed that there is a lower risk of infections in inflammatory joint diseases in comparison to connective tissue diseases and vasculitides. The increased risk of infections is determined by multiple factors, whereby the underlying factors are classified into three main categories: patient-related factors (age, comorbidities, lifestyle), disease-related factors (immunological dysfunction as part of the disease pathophysiology) and drug-related factors (type and dosage of the immunosuppression and/or immunomodulation). An improved understanding of the complexity of these associations enables the optimization of treatment and disease control taking the individual risk factors into account, with the aim of a significant reduction in the risk of infections.

Joint Statement (DZK, DGRh, DDG) on the Tuberculosis Risk with Treatment Using Novel Non-TNF-Alpha Biologicals

BACKGROUND

 While the risk of tuberculosis (TB) reactivation is adequately documented in relation to TNF-alpha inhibitors (TNFi), the question of what the tuberculosis risk is for newer, non-TNF biologics (non-TNFi) has not been thoroughly addressed.

METHODS

 We conducted a systematic review of randomized phase 2 and phase 3 studies, and long-term extensions of same, published through March 2019. Of interest was information pertaining to screening and treating of latent tuberculosis (LTBI) in association with the use of 12 particular non-TNFi. Only rituximab was excluded. We searched MEDLINE and the ClinicalTrial.gov database for any and all candidate studies meeting these criteria.

RESULTS

 677 citations were retrieved; 127 studies comprising a total of 34,293 patients who received non-TNFi were eligible for evaluation. Only 80 out of the 127 studies, or 63 %, captured active TB (or at least opportunistic diseases) as potential outcomes and 25 TB cases were reported. More than two thirds of publications (86/127, 68 %) mentioned LTBI screening prior to inclusion of study participants in the respective trial, whereas in only 4 studies LTBI screening was explicitly considered redundant. In 21 studies, patients with LTBI were generally excluded from the trials and in 42 out of the 127 trials, or 33 %, latently infected patients were reported to receive preventive therapy (PT) at least 3 weeks prior to non-TNFi treatment.

CONCLUSIONS

 The lack of information in many non-TNFi studies on the number of patients with LTBI who were either excluded prior to participating or had been offered PT hampers assessment of the actual TB risk when applying the novel biologics. Therefore, in case of insufficient information about drugs or drug classes, the existing recommendations of the German Central Committee against Tuberculosis should be applied in the same way as is done prior to administering TNFi. Well designed, long-term "real world" register studies on TB progression risk in relation to individual substances for IGRA-positive cases without prior or concomitant PT may help to reduce selection bias and to achieve valid conclusions in the future.

[Most important vaccinations in patients with rheumatological diseases and why]

Lange Zeit schienen die meisten Infektionen beherrschbar geworden zu sein. Hierzu haben besonders auch Impfungen beigetragen. In den letzten Jahren gefährden neu aufgetretene bakterielle Infektionen durch multiresistente Erreger und Virusinfektionen wie das Chikungunya-Virus, Influenzaepidemien oder aktuell auch COVID-19 die Weltbevölkerung. Dies gilt in besonderer Weise für von rheumatologischen Erkrankungen Betroffene, die oft zusätzlich einer immunsuppressiven Therapie bedürfen und damit besonders durch Infektionen gefährdet sind. Impfungen können die Betroffenen sowohl individuell wie auch durch die Erzeugung einer Herdenimmunität schützen und stellen somit ein wichtiges Instrument dar, um die Morbidität und Mortalität durch Infektionen zu vermindern. Die Kenntnis über Indikation und Anwendung der einzelnen Impfungen ist für eine konsequente Umsetzung der aktuellen Empfehlungen besonders wichtig.

Simple screening tools predict death and cardiovascular events in patients with rheumatic disease

OBJECTIVES

Patients with rheumatic disease (RD) have an increased mortality risk compared with the general population, mainly due to cardiovascular disease (CVD). We aimed to identify patients at high risk of CVD and mortality by comparing three screening tools suitable for clinical practice.

METHOD

In this prospective, single-centre study, consecutive patients with rheumatoid arthritis (RA), systemic autoimmune disease (SAI), or spondyloarthritides (SpA) including psoriatic arthritis underwent a comprehensive cardiovascular risk assessment. Patients were predefined as being at high risk for cardiovascular events or death if any of the following were present: European Systematic COronary Risk Evaluation (SCORE) ≥ 3%, N-terminal pro-brain natriuretic peptide (NT-proBNP) ≥ 200 pg/mL, or any pathological electrocardiogram pattern.

RESULTS

The patient population (n = 764) comprised 352 patients with RA, 260 with SAI, and 152 with SpA. After a median follow-up of 5.2 years, 6.0% of RD patients had died (7.0%, 7.2%, and 1.4% of patients in the RA, SAI, and SpA subgroups), and 5.0% had experienced a cardiovascular event (5.0%, 6.4%, and 2.8%, respectively). For all RD patients and the RA and SAI subgroups, NT-proBNP ≥ 200 pg/mL and SCORE ≥ 3% identified patients with a 3.5-5-fold increased risk of all-cause death and cardiovascular events. Electrocardiogram pathology was associated with increased mortality risk, but not with cardiovascular events.

CONCLUSION

NT-proBNP ≥ 200 pg/mL or SCORE ≥ 3% identifies RA and SAI patients with increased risk of cardiovascular events and death. Both tools are suitable as easy screening tools in daily practice to identify patients at risk for further diagnostics and closer long-term follow-up.

[Safety of antirheumatic drug treatment in the elderly]

Mainly due to the general demographic changes and decreasing mortality in rheumatic diseases based on therapeutic progress, the proportion of older patients treated by rheumatologists is growing. Drug treatment in the elderly, however, harbors certain risks including age-specific pharmacokinetic features and high rates of multimorbidity and polypharmacy resulting in a risk of drug interactions and adherence problems. Nevertheless, older patients suffering from rheumatic diseases ought to be treated with the same intensity and same targets as the younger counterparts. Bearing all these facts in mind it is a balancing act for rheumatologists to find an optimal treatment for the individual elderly patient. Fear of risks should not lead to hesitant use of drugs leaving these patients alone with treatment deficits, as some studies have suggested.

Screening for latent tuberculosis infection: performance of tuberculin skin test and interferon-γ release assays under real-life conditions

Objectives

To characterise optimal screening strategies for latent tuberculosis infection (LTBI) prior to the initiation of anti-tumour necrosis factor therapy.

Methods

Patients in 62 German rheumatology centres were evaluated for LTBI. Each patient was screened with a tuberculin skin test (TST) and one form of an interferon-γ release assay (IGRA), either TSPOT.TB (TSPOT) or Quantiferon TB Gold (QFT).

Results

A total of 1529 patients with rheumatological disease were tested with a TST, 844 with TSPOT and 685 with QFT. TST was positive in 11.3% (n=173). The prevalence of LTBI was 8.0% when defined as a positive TST and no previous Bacille Calmette-Guérin (BCG) vaccination and 7.9% when based on a positive IGRA. Combining both estimates increased the prevalence of LTBI to 11.1%. Clinical risk factors for LTBI were found in 122 patients (34 with a history of prior TB, 81 close contacts and 27 with suggestive chest x-ray lesions). A compound risk factor (CRF) was defined as the presence of at least one of these three risk factors. Statistical analyses were conducted to examine the association between CRF and LTBI test outcomes. In multivariate analysis, TST was influenced by CRF (OR 6.2; CI 4.08 to 9.44, p<0.001) and BCG vaccination status (OR 2.9; CI 2.00 to 4.35, p<0.001). QFT and TSPOT were only influenced by CRF (QFT: OR 2.6; CI 1.15 to 5.98, p=0.021; TSPOT: OR 8.7; CI 4.83 to 15.82, p<0.001). ORs and the agreement of TST and IGRA test results varied by rheumatological disease.

Conclusion

LTBI test results in an individual patient need to be considered in the context of prior BCG vaccination and clinical risk factors. In patient populations with low rates of TB incidence and BCG vaccination, the use of both TST and IGRA may maximise sensitivity in detecting LTBI but may also reduce specificity.

[Tuberculosis : diagnostics and prophylaxis]

Infection with Mycobacterium tuberculosis causes primarily formation of granulomatous tubercles in the lungs. In the absence of any clinical symptoms it is named latent tuberculosis infection which can be an origin of reactivation, especially as a consequence of an impaired response of the immune system. Complete anamnesis, radiographic methods and bacteriological analysis (microscopy, culture, PCR) are useful for diagnosis of tuberculosis. Since 2005 newer in vitro tests are available using interferon-gamma release assays (IGRAs). Compared to the tuberculin skin test it is possible to differentiate between infection with M. tuberculosis and individuals vaccinated with the Bacillus Calmette-Guérin (BCG) vaccine. These new in vitro tests are part of a screening procedure which has to be performed before starting immunosuppressive therapy with tumor necrosis factor-alpha (TNF-α) inhibitors. In cases of latent tuberculosis infection administration of isoniazid for 9 months is recommended.

[Vaccinations in rheumatology]

Patients with autoimmune or rheumatic diseases are at increased risk for infectious complications due to immunosuppressive therapy and/or the underlying immunological disease itself. To date, the consistent use of vaccinations in this patient group has been limited due to concerns about flair-ups or lack of efficacy. In prospective studies neither an increased risk of disease flair-ups nor of initiation of autoimmune disorders was found as yet; however, the data is still considered insufficient (small studies including only patients in remission). Vaccination with non-live vaccines can generally be regarded as safe and relatively effective, even in patients on immunosuppressive therapy. Since the immune response to vaccination may be markedly impaired depending on the medication used and the underlying autoimmune disease, monitoring of both serum titers and of patients' vaccination schedules should form an integral part of rheumatological care.

Exacerbation of Whipple's disease associated with infliximab treatment

A 34-year-old man with chronic inflammatory joint disease and recurrent fever over 6 years was diagnosed as having Still's disease. Treatment with corticosteroids and azathioprine was ineffective. Therefore, infliximab/ methotrexate was started. The patient subsequently developed a wasting disease with rapid weight loss, erythema nodosum, diarrhoea, progressive lymph node enlargement, and a sigmoido-vesical fistula. Histological analysis of several enlarged lymph nodes, the margins of the fistula, and the small bowel established the diagnosis of Whipple's disease (WD). The presence of Tropheryma whipplei (Tw) DNA in the tissues was confirmed by polymerase chain reaction (PCR). Careful re-evaluation of biopsies taken from the ileum and the liver 2 years earlier, which at that time was not judged to be diagnostic for WD, retrospectively showed subtle histological signs of WD and were positive for Tw DNA. In summary, infliximab treatment seems to increase the risk of exacerbation of WD. WD should be carefully ruled out prior to application of tumour necrosis factor-alpha (TNF-alpha) blockade.

TNF-like weak inducer of apoptosis inhibits proinflammatory TNF receptor-1 signaling

Soluble TNF-like weak inducer of apoptosis (TWEAK) trimers induce, in a variety of cell lines, translocation of cytosolic tumor necrosis factor (TNF) receptor-associated factor-2 (TRAF2) to a triton X-100-insoluble compartment without changes in the total cellular TRAF2 content. TWEAK-induced TRAF2 translocation is paralleled by a strong increase in nuclear factor kappaB 2 (NFkappaB2)/p100 processing to p52, indicating that TRAF2 redistribution is sufficient for activation of the alternative NFkappaB pathway. In accordance with the crucial role of TRAF2 in proinflammatory, anti-apoptotic TNF receptor-1 (TNFR1) signaling, we observed that TWEAK-primed cells have a reduced capacity to activate the classical NFkappaB pathway or JNK (cJun N-terminal kinase) in response to TNF. Furthermore, TWEAK-primed cells are sensitized for the TNFR1-mediated induction of apoptotic and necrotic cell death. Notably, the expression of the NFkappaB-regulated, TRAF2-interacting TRAF1 protein can attenuate TWEAK-induced depletion of the triton X-100-soluble TRAF2 fraction and improve TNFR1-induced NFkappaB signaling in TWEAK-primed cells. Taken together, we demonstrate that soluble TWEAK desensitizes cells for proinflammatory TNFR1 signaling and thus identify TWEAK as a modifier of TNF signaling.

[Phlegmonous gastritis in a 44-year-old woman on immunosuppressive therapy]

HISTORY AND ADMISSION FINDINGS

A 44-year-old woman was on long-term immunosuppressive therapy with leflunomide and adalimumab for rheumatoid arthritis. She was admitted to the emergency room with diffuse abdominal pain of sudden onset. On physical examination she had rebound tenderness in all four abdominal quadrants.

INVESTIGATIONS

The white blood cell count was 3300/l, C-reactive protein 25 mg/dl and serum lactate 10 mmol/l. Abdominal computed tomography revealed a diffusely thickened gastric wall and ascites. At explorative laparotomy 1000 ml of a cloudy peritoneal fluid were aspirated and found to be negative for bacteria. But a culture of a mesenterial smear grew streptococci group A. Intra-operative endoscopy showed extensive hemorrhagic gastritis. Because there was no perforation or transmural necrosis gastric resection was not performed.

DIAGNOSIS, TREATMENT AND COURSE

Diffuse thickening of the gastric wall, extended mucosal necrosis and the peritoneal finding of streptococci in an immunocompromised patient suggested the diagnosis of phlegmonous gastritis. On treatment with antibiotics and proton pump inhibitor the patient made a slow recovery over the following eight weeks. Nine months after the event an asymptomatic antral stricture was noticed at follow-up gastroscopy.

CONCLUSION

Phlegmonous gastritis is a rare but life-threatening complication in immunosuppressed patients.

[Cytokines]

Cytokine driven inflammation is a common feature in autoimmune diseases. Cytokines are needed under physiological conditions within the innate and adaptive immune systems to control infectious diseases and neoplastic disorders by regulation of the cell cycle and apoptosis. Cytokines can also be found in persistently increased concentrations in inflamed tissues within autoimmune diseases. Therefore, the modulation of cytokines seems to be a worthwhile therapeutic approach. With TNFalpha and Il-1, two key cytokines in rheumatoid arthritis have been identified. Their inhibition leads to a convincing clinical benefit. In the near future, inhibition of additional cytokines, such as Il-6 or Il-15, will likely open new beneficial strategies.

[Systemic sclerosis]

Systemic sclerosis (SSc; syn. systemic scleroderma) is a rare autoimmune disorder with characteristic cutaneous manifestations. Prevalence in women is fivefold higher than in men. The course of the disease is slowly progressive with a variable degree of internal organ involvement due to fibrosis and obliteration of small vessels. The diffuse form shows more frequent and severe organ manifestations compared to the limited form. Increased mortality is particularly related to a cardiopulmonary involvement leading to a 5-year survival of around 75%. Treatment indications are dependent on the severity of the disease. In the acute state, immunosuppressive agents are needed in case of significant organ involvement. Vasodilative drugs are often used for the symptomatic treatment of Raynaud's phenomenon.

[Treatment of rheumatoid arthritis (RA) with anticytokines]

In the hands of an experienced rheumatologist and in adherence to the contraindications named in the article, anticytokines such asTNF-alpha blockers or interleukin-1 antagonists are regarded as relatively reliable, are well tolerated and in many cases, are very effective. Especially when used in combination with methotrexate, they demonstratively lower the disease activity score and significantly slow the radiographic progression.Thus, anticytokines are currently the most effective therapy for RA. An additional advantage compared to conventional DMARD is the rapid onset of action (usually within two to four weeks).TNF-alpha blockers are also presently employed in numerous other chronic inflammatory diseases. The efficacy of anticytokines in psoriasis and psoriatic arthritis, ankylosing spondylitis, juvenile arthritis and Crohn's disease has been proven.

NSAR und Coxibe: aktueller Stand

NSAIDs (non steroidal anti-inflammatory drugs) are a crucial component for the therapy of pain induced by inflammatory and degenerative joint diseases. Nevertheless their known therapeutic efficacy is contrasted by significant side effects. The recently developed selective COX-2-inhibitors appear to have a better gastrointestinal safety profile, especially relevant to patients with an increased risk for gastrointestinal ulcers and bleeding. However, this effect may similarly be reached by the combination of NSAIDs with proton pump inhibitors. Recent data relate to an elevated myocardial infarction rate in patients using COX-2-inhibitors. This risk may also occur in conventional NSAIDs. Therefore an individual risk calculation is necessary before COX-2-inhibitors or NSAIDs are used. Treatment should be performed with the lowest dosage for the shortest time possible. Combination therapy with salicylic acid seems to abolish the protective effect of COX-2-inhibitors in the GI-tract. Definite risk factors for the treatment with NSAIDs and COX-2-inhibitors have to be defined in further studies providing the best treatment schedule for an individual patient.

Improvement of refractory rheumatoid arthritis after depletion of B cells

OBJECTIVE

B cells are involved in the pathogenesis of rheumatoid arthritis (RA). To evaluate the effect of therapeutic B-cell depletion for treatment of RA, an open label study has been performed using the B-cell depleting anti-CD20 antibody rituximab.

METHODS

Five patients with refractory RA were treated weekly with four infusions of rituximab (375 mg/m2) alone, or in combination with ongoing methotrexate (MTX). Patients were followed for at least 44 weeks and monitored for safety and tolerability of treatment.

RESULTS

Treatment could be performed without serious side effects and resulted in peripheral B-cell depletion lasting between 36 weeks up to > 1 year. The follow-up revealed no significant treatment-associated side effects. At 22 weeks, 4/5 patients showed a significant improvement (> 1.2) of the Disease Activity Score (DAS28). The mean DAS28 of all patients declined from 6.2 to 4.1. At 44 weeks there was one drop-out, another patient still had a sustained response, and three patients showed slowly increasing disease activity (mean DAS28 of the remaining four patients: Week 0: 6.0; Week 22: 3.85; Week 44: 5.6). Despite relatively constant immunoglobulin levels, rheumatoid factor levels decreased parallel to disease activity.

CONCLUSION

In patients with refractory RA, B-cell depletion with rituximab is safe and well tolerated. A reduction of disease activity could be observed, which eventually deteriorated after B-cell repopulation. The findings give more evidence for B-cell targeted therapies in RA.

High resolution ultrasound detects a decrease in pannus vascularisation of small finger joints in patients with rheumatoid arthritis receiving treatment with soluble tumour necrosis factor alpha receptor (etanercept)

OBJECTIVE

High resolution ultrasound (HRUS) was used to investigate the effects of tumour necrosis factor alpha (TNFalpha) blockade on pannus formation and vascularisation of small finger joints in patients with active rheumatoid arthritis (RA).

METHODS

Five patients with active RA were treated with etanercept, a soluble TNFalpha receptor protein, for one month. Before, during, and after treatment the patients were followed up by clinical rheumatological examination, determination of their subjective pain score, blood chemistry, and by HRUS of the second metacarpophalangeal (MCP) joint of the right hand.

RESULTS

One month after treatment with etanercept, rheumatological examination showed a significant decrease in a modified single joint rheumatic disease activity index (from 2.9 (SD 0.2) to 1.2 (0.7); p<0.05) in all patients. Moreover, a significant decrease in the general pain score (from 4.7 (0.4) to 1.8 (0.6); p<0.05) and in C reactive protein (CRP) levels was seen (from 3.02 (0.9) to 0.24 (0.1); p<0.05). Concordantly, HRUS showed a significant reduction in pannus vascularisation of the MCPII joints (from 23,602 (5339) to 2907 (1609) colour signals/region of interest, CS/ROI; p<0.001). Pearson's correlation coefficient between the results obtained by HRUS and the clinical response was 0.85.

CONCLUSION

HRUS is promising as an additional useful method in the assessment of RA activity, and probably also in monitoring therapeutic responses.

STAT6 and the regulation of CD23 expression in B-chronic lymphocytic leukemia

High CD23 expression is a hallmark of B-CLL cells. It is lost during in vitro culture and can be reinduced by IL-4, albeit to a lower extent than in normal B cells. To elucidate the events controlling CD23 expression in B-CLL cells, the IL-4 mediated induction of STAT6 was investigated. Western-blot analysis demonstrated that B-CLL cells contain comparable amounts of STAT6. Electrophoretic mobility shift assays (EMSA) showed no constitutive nuclear translocation of STAT6. IL-4 induced the translocation of STAT6 in B-CLL cells from all 22 patients investigated. The increase was transient, dose and time dependent without a distinct difference between B-CLL cells and non-malignant B cells. However, in contrast to normal B lymphocytes no strict correlation between CD23 expression and STAT6 activation was detected in B-CLL. Therefore further signalling pathways and transcription factors in addition to STAT6 have to be activated to explain the high expression of CD23 in B-CLL cells. For example, STAT1 which is induced by IFN-gamma and binds to the classical STAT6 site. It might be involved in the strong induction of CD23 on B-CLL cells after cotreatment with IL-4 and IFN-gamma, while in non-malignant B lymphocytes IFN-gamma leads to a reduction of IL-4 mediated CD23 expression.

Inhibition of T cell/B cell interaction by B-CLL cells

The course of disease in patients suffering from chronic lymphocytic leukemia (CLL) is determined by a profound dysregulation of the immune system. The resulting immune suppression is the main cause of death in those patients. In the present study we addressed the question of whether leukemic B cells (B-CLL) are able to suppress regular T cell/B cell interaction. Activated CD4+ T cell clones induce expression of the early activation antigen CD23 on B lymphocytes in vitro. Under conditions used, this B cell activation event was dependent upon direct T cell contact. Addition of certain bystander B-CLL cells or normal B lymphocytes resulted in a cell number-dependent inhibition of B cell induction. This seems to reflect the competition of B-CLL cells for a cell contact-mediated T cell helper signal. By using CD40 ligand transfected fibroblasts as a substitute for T cell help, we show that the same B-CLL cells also suppress CD40 ligand-mediated B cell activation. B-CLL cells differ in their ability to inhibit CD40 ligand-mediated B cell activation. Some B-CLL cases (eight out of 14) are unable to compete for the T cell or CD40 ligand-mediated signal, even though they can functionally interact with CD40 ligand and thereby get activated themselves. In addition, these results indicate that the observed inhibition is not a result of cell crowding by merely reducing the chance of specific B cell/T cell interactions. Collectively, these data indicate that B-CLL cells are able to inhibit the interaction of activated T lymphocytes with normal B lymphocytes in vitro. Perturbed T cell/B cell interaction may represent an important mechanism underlying the various defects of the specific immune system observed in patients suffering from B-CLL.

Nuclear NF-ATp is a hallmark of unstimulated B cells from B-CLL patients

B lymphocytes from the peripheral blood of patients with chronic lymphocytic leukaemia (CLL) were analysed for the nuclear presence and DNA binding of a panel of transcription factors which are involved in the gene control of lymphoid cells. The following transcription factors were studied: the Octamer factors Oct-1 and Oct-2, members of the AP-1 factor family, NF-AT factors, in particular NF-ATp, and members of the Rel/NF-kB family. We show that the constitutive nuclear translocation of NF-ATp, a member of the growing family of NF-AT factors, is a hallmark of nonstimulated B cells from CLL patients that distinguishes B-CLL cells from 'normal' B lymphocytes. Constitutive nuclear appearance was also observed for NF-kB2/p52. Constitutive binding of further factor proteins to DNA, such as JunD, c-Fos and FosB, was detected in several patients whereas the localisation and DNA binding of other factors such as c-Jun, RelA/p65 and c-Rel was unaltered. It is remarkable that in B-CLL cells the nuclear appearance and DNA binding of specific transcription factors is dramatically affected whereas other members of the same factor family remained unaltered in these leukemic cells. It remains to be shown which molecular events lead to the specific 'pre-activation', i.e. constitutive nuclear translocation and DNA binding, of these members of NF-AT, NF-kB and AP-1 factor families.

[Sarcoidosis in monozygotic twins]

Identical (monozygotic) female twins both simultaneously developed acute sarcoidosis with unusual manifestations. Additional to pulmonary involvement they both also had hypercalcaemia with compensated renal failure. When seen at the age of 33 years, these findings were more marked in one of them (case 2) than in the other, and she also had granulomatous conjunctivitis, while in the other one (case 1) the dominant sign was widespread lymph node enlargement. Both were also found by magnetic resonance imaging to have multiple lesions in the white matter, interpreted as the morphological correlate of neurosarcoidosis. But they caused clinical symptoms (visual disorder, unsteady gait) in only one sister (case 1). Treatment with prednisolone largely normalized the lung functions in case 2, completely in case 1, and renal functions in both. But when the daily prednisolone dose was reduced to below 10 mg, the pulmonary symptoms recurred. These observations indicate that even in chronic sarcoidosis acute episodes may occur, with involvement of multiple organs and other rare complications. The manifestations of the underlying disease in identical twins and the similarities of its course in the two sisters underline the possible role of genetic factors in the pathogenesis of sarcoidosis.

Alterations of thymus cortical epithelium and interdigitating dendritic cells but no increase of thymocyte cell death in the early course of simian immunodeficiency virus infection

The role of the thymus in the pathogenesis of simian acquired immunodeficiency syndrome was investigated in 18 juvenile rhesus monkeys (Macaca mulatta). The thymus was infected from the first week post-SIVmac inoculation, but the amount of virus-positive cells was very low (< 1 in 10(4) T cells) as demonstrated by polymerase chain reaction and in situ hybridization. First morphological alteration was a narrowing of the cortex at 12 and 24 wpi. Morphometry revealed no increase of pyknotic T cells but a decrease of the proliferation rate and flow cytometry showed a reduction of the immature CD4+/CD8+ double-positive T cells. Ultrastructural analysis revealed vacuolization, shrinkage, and finally cytolysis of the cortical epithelial cells and the interdigitating dendritic cells. Immunofluorescence staining exhibited a widespread loss of cortical epithelial cells. This damage to the thymic microenvironment could explain the breakdown of the intrathymic T cell proliferation. It preceded fully developed simian acquired immunodeficiency syndrome and is therefore considered to play a major role in its pathogenesis.

Early phenotypic and functional alterations in lymphocytes from simian immunodeficiency virus infected macaques

Phenotypic and functional changes in lymphocytes from rhesus monkeys (Macaca mulatta) were investigated during the first 6 months after infection with SIV mac 32H. Animals preimmunized with keyhole limpet hemocyanin (KLH) were sacrificed 1, 3, 6, 12, and 24 weeks post infection. Subset composition and function of lymphocytes from blood, spleen, lymph node and thymus were analysed. In addition to a rapid decline in CD4/CD8 ratios, a massive reduction in CD29+ CD4+ cells was seen in the periphery. Although depletion of this subset was observed throughout the course of this experiment, the loss of proliferative T cell responses was most pronounced very early after infection and partially recovered after Month 3. Polyclonal cytotoxic responses were only slightly affected. In the thymus, a gradual, but moderate loss of CD4+CD8+ immature thymocytes, and a relative increase in both CD4+ and CD8+ mature subsets was observed. Infectious virus was readily recovered from homogenates of lymph node and spleen, but not of thymus tissue. Interestingly, however, virus was detected in thymocytes from all infected animals by cocultivation with a simian immunodeficiency virus (SIV) susceptible cell line.

Mechanism of MHC class I downregulation in HIV infected cells

HIV infection of CD4+ peripheral blood lymphocytes leads to a loss of MHC class I molecules on the surface of the infected cells as detectable by monoclonal antibody staining and flow cytometry. Incubation of the infected cells at 26 degrees C or treatment at 37 degrees C with peptides leads to upregulation of MHC class I to levels equal to those found on uninfected cells cultured under the same conditions. The data suggest that, after HIV infection, the mechanisms responsible for peptide generation, peptide transport and thus stable association between peptides and MHC class I molecules are severely affected.