The C-terminus of amelogenin enhances osteogenic differentiation of human cementoblast lineage cells.

BACKGROUND AND OBJECTIVES: Amelogenin proteins are the major constituent of developing extracellular enamel matrix and are believed to have an exclusively epithelial origin. Recent studies have suggested that amelogenins might induce the differentiation and maturation of various cells, including cementoblast lineage cells. However, the residues comprising the active site of amelogenin remain unclear. The purpose of this study was to identify the active site region of amelogenin by studying the effects of amelogenin fragments on the osteogenic differentiation of cementoblasts. MATERIAL AND METHODS: Amelogenin fragments lacking the C-terminus (rh163) and N-terminus (rh128) and a fragment consisting of the C-terminal region of rh174 (C11 peptide) were synthesized and purified. Human cementoblast lineage cells were cultured in osteogenic differentiation medium and treated with 0, 10, 100 or 1000 ng/mL of rh163, rh128 or C11 peptide. The mRNA levels of bone markers were examined by real-time polymerase chain reaction analysis. Alkaline phosphatase activity and calcium deposition were also determined. Mineralization was evaluated by alizarin red staining. RESULTS: The osteogenic differentiation of human cementoblast lineage cells was significantly enhanced by treatment with rh128 or C11 peptide, whereas rh163 had no significant effect as compared with untreated controls. CONCLUSIONS: The C-terminus of amelogenin promotes the osteogenic differentiation of human cementoblast lineage cells, indicating the possible utility of C11 peptide in periodontal tissue regeneration.

Tongue-palatal contact changes in patients with skeletal mandibular prognathism after sagittal split ramus osteotomy: an electropalatography study.

The purpose of this study was to investigate the changes in tongue-palatal contact patterns using electropalatography (EPG) before and after sagittal split ramus osteotomy (SSRO) in patients with mandibular prognathism. Nine clients who underwent SSRO for mandibular setback and seven control subjects were participated in this study. Tongue-palatal contact patterns for /t/, /s/ and /k/ production were investigated using EPG before surgery and 3 months after surgery. The mean value of whole total of palate contact (WT) in the maximum contact frame was examined before and after SSRO. The correlation quantity between the change of center of gravity (COG) value and the amount of mandibular setback was also evaluated. The mean value of WT for /t/ and /s/ significantly increased after SSRO, and the EPG pattern became normal. However, a remarkable change in WT for /k/ was not observed, and the mean value was significantly larger in the SSRO group before and after surgery than in the control group. A negative correlation between COG variation and the amount of mandibular setback for /t/ and positive correlation for /s/ was observed. This study demonstrated that tongue-palatal contact patterns for /t/ and /s/ articulation improved clearly after SSRO. There was a significant correlation between COG variation and the amount of mandibular setback. However, no significant change was detected through perceptual assessment before and after SSRO. Further investigation is needed to determine whether these results will change over time.

The effect of magnetic field during freezing and thawing of rat bone marrow-derived mesenchymal stem cells.

Previous studies showed that a programmed freezer with magnetic field can maintain a high survival rate of mesenchymal stem cells (MSCs). The purpose of this study was to evaluate the influences of magnetic field during freezing and thawing on the survival of MSCs isolated from rat bone marrow. The cells were frozen by a normal programmed freezer or a programmed freezer with magnetic field (CAS-LAB1) and cryopreserved for 7 days at -150 °C. Then, the cells were thawed in the presence or absence of magnetic field. Immediately after thawing, the number of surviving or viable cells was counted. The cell proliferation was examined after 1-week culture. Cryopreserved MSCs which were frozen by a normal freezer or a CAS freezer were transplanted into bone defects artificially made in calvaria of 4-week-old rats. Non-cryopreserved MSCs were used as a control. The rats were sacrificed at 8, 16, or 24 weeks after transplantation and the bone regeneration area was measured. Proliferation rates of MSCs after 1 week were significantly higher in the CAS-freezing-thawing group than in the CAS-freezing group. The extent of new bone formation in the CAS-freezing-thawing group tended to be larger than in CAS-freezing group 24 weeks after transplantation. These results suggest that a magnetic field enhances cell survival during thawing as well as freezing.

Cranial suture-like gap and bone regeneration after transplantation of cryopreserved MSCs by use of a programmed freezer with magnetic field in rats.

Mesenchymal stem cells (MSCs) can be used for regeneration of various organs and tissues. A previous study revealed that cryopreserved MSCs, which were frozen by a programmed freezer with a magnetic field (Cells Alive System: CAS) and cryopreserved for 7 days in a -150°C deep freezer, can maintain high survival and proliferation rates while retaining both adipogenic and osteogenic differentiation abilities. The purpose of this study was to examine MSC viability and tissue regenerative ability after long-term cryopreservation using a CAS freezer. MSCs were isolated from rat femora bone marrow and cryopreserved in a -150°C deep freezer (CAS group) or directly cryopreserved in a deep freezer (Direct group). After 3 years, the cells were thawed and the number of viable cells was counted. Cell proliferation was also examined after 14 days in culture. For histological examination, forty 4-week-old Fischer 344 male rats received bone and sagittal suture defects with a diameter of 6.0mm, and MSCs (CAS or Direct group) cryopreserved for 1 year were grafted with membranes. Non-cryopreserved MSCs (Control group) were transplanted to an additional twenty rats. The rats were sacrificed at 4, 8, 16, and 24 weeks after surgery. The parietal bones, including the sagittal suture, were observed under a light microscope and the extent of bone regeneration was measured. Our results indicate that MSCs survival and proliferation rates were significantly higher in the CAS group than in the Direct group. In the Control and CAS groups, a large amount of new bone formation and a suture-like gap was identified 24 weeks after transplantation, whereas only a small amount of new bone formation was observed in the Direct group. These results suggest that the CAS freezer is amenable to long-term cryopreservation of MSCs, which can be applied to the regeneration of various tissues, including bone tissue with suture-like gap formation.

Effects of occlusal hypofunction and its recovery on PDL structure and expression of VEGF and bFGF in rats.

OBJECTIVES: The purpose of this study was to clarify whether occlusal hypofunction and its recovery affect the structure of the periodontal ligament (PDL) and expression of vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (bFGF) in rats. MATERIALS AND METHODS: Forty-eight Wistar rats aged 5 weeks were used and randomly divided into three groups: the hypofunctional group (HG), recovery group (RG), and control group (CG). In HG and RG, appliances were attached to the maxillary and mandibular incisors. In HG, appliances were set for 11 weeks. In RG, appliances were set for 7 weeks. Appliances were then removed at 0, 1, 3, 7, 14, and 28 days. Untreated rats served as CG. Histological sections were prepared and immunohistochemically stained for VEGF and bFGF. Three groups were evaluated for PDL area and the number of VEGF and bFGF immunopositive cells in PDL. RESULTS: The number of immunopositive cells and PDL area in CG and RG were significantly larger when compared with HG, and PDL area in RG was similar to that in CG. In the recovery process, PDL area and number of VEGF-positive cells in PDL increased from days 0 to 7 and decreased from days 7 to 28. Conversely, the number of bFGF-positive cells in PDL increased significantly after day 1 and peaked at 28 days. CONCLUSIONS: This study suggests that occlusal stimuli regulate PDL area through expression of VEGF and bFGF in rat PDL. CLINICAL RELEVANCE: Occlusal stimuli are able to regulate the expression of VEGF and bFGF in PDL cells, and these growth factors may lead to alveolar bone remodeling in PDL.

Celecoxib exerts protective effects on extracellular matrix metabolism of mandibular condylar chondrocytes under excessive mechanical stress.

OBJECTIVE: Excessive mechanical stress is considered a major cause of temporomandibular joint osteoarthritis (TMJ-OA). High magnitude cyclic tensile strain (CTS) up-regulates pro-inflammatory cytokines and matrix metalloproteinases (MMPs) in chondrocytes, while selective cyclooxygenase (COX)-2 inhibition has been shown to be beneficial to cytokine-induced cartilage damage. However, the effect of selective COX-2 inhibitors on mechanically stimulated chondrocytes remains unclear. This study evaluated the effect of celecoxib, a selective COX-2 inhibitor, on extracellular matrix (ECM) metabolism of mandibular condylar chondrocytes under CTS. METHODS: Porcine mandibular chondrocytes were subjected to CTS of 0.5 Hz, 10% elongation with celecoxib for 24 h. The gene expressions of COX-2, MMPs, aggrecanase (ADAMTS), type II collagen and aggrecan were examined by real-time PCR. Also, prostaglandin E2 (PGE2) concentrations were determined using enzyme immunoassay kit. The levels of MMP and transcription factor NF-κB were measured by western blot while MMP activity was determined by casein zymography. RESULTS: The presence of celecoxib normalized the release of PGE2 and diminished the CTS-induced COX-2, MMP-1, MMP-3, MMP-9 and ADAMTS-5 gene expressions while recovered the downregulated type II collagen and aggrecan gene expressions. Concurrently, celecoxib showed inhibition of NF-κB and suppression of MMP production and activity. CONCLUSIONS: Celecoxib exerts protective effects on mandibular condylar chondrocytes under CTS stimulation by diminishing degradation and restoring synthesis of ECM.

Amelogenin enhances the osteogenic differentiation of mesenchymal stem cells derived from bone marrow.

Amelogenins are the major constituent of developing extracellular enamel matrix proteins and are understood to have an exclusively epithelial origin. Recent studies have demonstrated that amelogenins can be detected in other tissues, including bone marrow mesenchymal stem cells (MSCs), but the role of amelogenins in MSCs remains unclear. The purpose of this study was to examine the effect of recombinant human full-length amelogenin (rh174) on the osteogenic differentiation of cultured human MSCs. MSCs isolated from human bone marrow were cultured in osteoblastic differentiation medium with 0, 10 or 100 ng/ml rh174. The mRNA levels of bone markers were examined by real-time PCR analysis. Alkaline phosphatase (ALP) activity and calcium concentration were determined. Mineralization was evaluated by alizarin red staining. The mRNA levels of ALP, type I collagen, osteopontin and bone sialoprotein in the MSCs treated with rh174 became significantly higher than those in non-treated controls. Treatment of MSCs with rh174 also enhanced ALP activity and calcium concentration, resulting in enhanced mineralization, as denoted by high intensity of alizarin red staining. In conclusion, the present study showed that rh174 enhances the mineralization accompanied by the upregulation of bone markers in human bone marrow MSCs during osteogenic differentiation, suggesting a certain role of amelogenin in the modulation of osteogenic differentiation of MSCs.

Cor triatriatum sinister: an incidental finding in a patient with paroxysmal atrial fibrillation.

A 58-year-old male was referred for catheter ablation for atrial fibrillation. He was incidentally diagnosed with cor triatriatum sinister by preoperative transesophageal echocardiography and cardiovascular computed tomography. The patient has since been free from atrial fibrillation for over 24 months following successful electrical pulmonary vein isolation. The rapidly soaring number of cases undergoing catheter ablation for atrial fibrillation and imaging investigation prior to the procedure may increase the incidental detection of asymptomatic congenital heart diseases.

Correlation between genotype and supernumerary tooth formation in cleidocranial dysplasia.

INTRODUCTION: Cleidocranial dysplasia (CCD, MIM#119600), for which the responsible gene is RUNX2, is a genetic disorder characterized by hypoplasia or aplasia of the clavicles, patent fontanelles, and a short stature. Supernumerary teeth and delayed eruption and impaction of permanent teeth are frequently associated with CCD. Our previous study reported wide intrafamilial variation in supernumerary tooth formation associated with a mutation in the RUNT-domain of RUNX2, suggesting a low correlation between the genotype and supernumerary tooth formation. To further clarify this point, a more precise evaluation was performed. DESIGN: Gene mutational analysis of nine Japanese individuals with CCD was performed. Dental and skeletal characteristics were examined based on patient examinations and radiographs. RESULTS: Four different gene mutations, including one novel mutation in RUNX2 gene (NM_001024630), were identified. Among them, four individuals had the R225Q mutation, three siblings had the P224S mutation, and the other two individuals had different frame-shift mutations. Wide variations in supernumerary tooth formation were observed in individuals with identical gene mutations, and discordance was seen between monozygotic twins. Asymmetric supernumerary tooth formation was noted in five out of the nine individuals. CONCLUSION: Individuals with identical gene mutations showed a wide variation in the supernumerary tooth formation. Not only the genotype but also environmental factors and a complex system including epigenetics and copy number variation might regulate supernumerary tooth formation in CCD.

Biomechanical and biochemical characteristics of the mandibular condylar cartilage.

The human masticatory system consists of a mandible which is able to move with respect to the skull at its bilateral temporomandibular joint (TMJ) through contractions of the masticatory muscles. Like other synovial joints, the TMJ is loaded mechanically during function. The articular surface of the mandibular condyle is covered with cartilage that is composed mainly of collagen fibers and proteoglycans. This construction results in a viscoelastic response to loading and enables the cartilage to play an important role as a stress absorber during function. To understand its mechanical functions properly, and to assess its limitations, detailed information about the viscoelastic behavior of the mandibular condylar cartilage is required. The purpose of this paper is to review the fundamental concepts of the biomechanical behavior of the mandibular condylar cartilage. This review consists of four parts. Part 1 is a brief introduction of the structure and function of the mandibular condylar cartilage. In Part 2, the biochemical composition of the mandibular condylar cartilage is summarized. Part 3 explores the biomechanical properties of the mandibular condylar cartilage. Finally, Part 4 relates this behavior to the breakdown mechanism of the mandibular condylar cartilage which is associated with the progression of osteoarthritis in the TMJ.

Stress analysis in the mandibular condyle during prolonged clenching: a theoretical approach with the finite element method.

Parafunctional habits, such as bruxism and prolonged clenching, have been associated with functional overloading in the temporomandibular joint (TMJ), which may result in internal derangement and osteoarthrosis of the TMJ. In this study, the distributions of stress on the mandibular condylar surface during prolonged clenching were examined with TMJ mathematical models. Finite element models were developed on the basis of magnetic resonance images from two subjects with or without anterior disc displacement of the TMJ. Masticatory muscle forces were used as a loading condition for stress analysis during a 10 min clenching. In the asymptomatic model, the stress values in the anterior area (0.100 MPa) and lateral area (0.074 MPa) were relatively high among the five areas at 10 min. In the middle and posterior areas, stress relaxation occurred during the first 2 min. In contrast, the stress value in the lateral area was markedly lower (0.020 MPa) than in other areas in the symptomatic model at 10 min. The largest stress (0.050 MPa) was located in the posterior area. All except the anterior area revealed an increase in stress during the first 2 min. The present result indicates that the displacement of the disc could affect the stress distribution on the condylar articular surface during prolonged clenching, especially in the posterior area, probably leading to the cartilage breakdown on the condylar articular surface.

Observer performance in diagnosing osteoporosis by dental panoramic radiographs: results from the osteoporosis screening project in dentistry (OSPD).

Mandibular cortical erosion detected on dental panoramic radiographs (DPRs) may be useful for identifying women with osteoporosis, but little is known about the variation in diagnostic efficacy of observers worldwide. The purpose of this study was to measure the accuracy in identifying women at risk for osteoporosis in a worldwide group of observers using DPRs. We constructed a website that included background information about osteoporosis screening and instructions regarding the interpretation of mandibular cortical erosion. DPRs of 100 Japanese postmenopausal women aged 50 years or older who had completed skeletal bone mineral measurements by dual energy X-ray absorptiometry were digitized at 300 dpi. These were displayed on the website and used for the evaluation of diagnostic efficacy. Sixty observers aged 25 to 66 years recruited from 16 countries participated in this study. These observers classified cortical erosion into one of three groups (none, mild to moderate, and severe) on the website via the Internet, twice with an approximately 2-week interval. The diagnostic efficacy of the Osteoporosis Self-Assessment Tool (OST), a simple clinical decision rule based on age and weight, was also calculated and compared with that of cortical erosion. The overall mean sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of the 60 observers in identifying women with osteoporosis by cortical erosion on DPRs were 82.5, 46.2, 46.7, and 84.0%, respectively. Those same values by the OST index were 82.9, 43.1, 43.9, and 82.4%, respectively. The intra-observer agreement in classifying cortical erosion on DPRs was sufficient (weighted kappa values>0.6) in 36 (60%) observers. This was significantly increased in observers who specialized in oral radiology (P<0.05). In the 36 observers with sufficient intra-observer agreement, the overall mean sensitivity, specificity, PPV, and NPV in identifying women with osteoporosis by any cortical erosion were 83.5, 48.7, 48.3, and 85.7%, respectively. The mean PPV and NPV were significantly higher in the 36 observers with sufficient intra-observer agreement than in the 24 observers with insufficient intra-observer agreement. Our results reconfirm the efficacy of cortical erosion findings in identifying postmenopausal women at risk for osteoporosis, among observers with sufficient intra-observer agreement. Information gathered from radiographic examination is at least as useful as that gathered from the OST index.

Effects of fluoride on the interactions between amelogenin and apatite crystals.

Fluorosed enamel is more porous and less mineralized, possibly related to altered amelogenin-modulated crystal growth. The purpose of this study was to examine the role of fluoride in interactions between amelogenin and apatite crystals. Recombinant human amelogenin (rh174) was bound to carbonated hydroxyapatite containing various amounts of fluoride, and analyzed by protein assay, SDS PAGE, and AFM. Interactions between rh174 and fluoride were assayed by isothermal titration calorimetry (ITC). The initial binding rate of rh174, as well as total amount of rh174 bound to fluoride-containing carbonated hydroxyapatite, was greater than that in the control carbonated hydroxyapatite. Fluoride in solution at physiologic (5.3 micromolar, or 0.1 ppm) concentrations showed no significant effect on binding, but higher fluoride levels significantly decreased protein binding. ITC showed no interactions between fluoride and rh174. These results suggest that fluoride incorporation into the crystal lattice alters the crystal surface to enhance amelogenin binding, with no direct interactions between fluoride and amelogenin.

Reduced amelogenin-MMP20 interactions in amelogenesis imperfecta.

Amelogenin with a proline 41 to threonine mutation (P41T) is hydrolyzed at a lower rate by matrix metalloproteinase 20 (MMP20), resulting in an inherited tooth enamel defect, amelogenesis imperfecta (AI). The aim of this study was to elucidate the effect of P41T on the interactions between amelogenin and MMP20, which may contribute to the formation of this type of AI. The interactions of a recombinant wild-type human amelogenin and its P41T mutant with recombinant human MMP20 were compared by substrate competition assay, pull-down assay, and surface plasmon resonance (SPR). The results showed that the binding of the P41T mutant amelogenin for MMP20 was significantly lower than that of wild-type amelogenin. Our study supports a model in which the P41T mutation reduces the interactions between amelogenin and MMP20, leading to decreased degradation of amelogenin by MMP20, and resulting in AI.

Expression and activity of Runx2 mediated by hyaluronan during chondrocyte differentiation.

During endochondral ossification, the production of hyaluronan (HA) is strictly and selectively regulated by chondrocytes, with a temporal peak at the hypertrophic stage. This study was conducted to clarify the effects of HA on expression and activity of runt-related gene 2 (Runx2), a potent transcription factor for chondrocyte differentiation in hypertrophic chondrocytes. Immature chondrocytes from an ATDC5 cell line were cultured and differentiated in DMEM/Ham's F12 with pre-defined supplements. Using real-time PCR, the gene expressions of type II collagen, MMP-13, HAS2, and Runx2 in cultured chondrocytes were analysed from days 0 to 18 of cell differentiation. The activity and expression of Runx2 in hypertrophic chondrocytes were analysed after the treatment with HA oligosaccharide (HAoligo) using AML-3/Runx2 binding, real-time PCR and Western blot analysis. The effects of pre-incubation of anti-CD44 antibody on Runx2 expression were also examined. Expression of type X collagen and Runx2 mRNAs reached a maximum at the terminal differentiation of chondrocytes. The activity and expression of Runx2 was significantly inhibited in hypertrophic chondrocytes treated with HAoligo compared to the untreated controls. High molecular weight-HA did not affect the expression or activity of Runx2. The expression of Runx2 mRNA was significantly decreased in hypertrophic chondrocytes treated with anti-CD44 antibody. These results suggest that HAoligo may affect the terminal differentiation of chondrocytes during the endochondral ossification by inhibiting the expression and activity of Runx2.

Effects of tooth loss and denture wear on tongue-tip motion in elderly dentulous and edentulous people.

The purpose of this study was to clarify quantitatively the differences in tongue-tip motion among the dentulous elderly people and also among the elderly edentulous, both with and without their dentures and, to identify the influence of tooth loss and denture wear on tongue-tip motion. Fourteen young dentulous people, 12 elderly dentulous people and 13 elderly edentulous people participated in this study. Subjects were asked to swallow a 10 mL barium sulfate solution three times. The elderly edentulous people were asked to swallow the solution while wearing dentures and with dentures removed. Functional swallowing was recorded on cine-film with a digital subtraction angiography system. Lateral cinefluorography images were obtained from seated subjects. Using a cine-projector, the movements of the tongue surface were traced as dots and lines frame by frame on a single tracing sheet within a definite period of time from the beginning of the oral phase to the end of the pharyngeal phase. With counting the number of 'trajectories' of tongue-tip motion, tongue movements were classified as 'stable' and 'hyperactive' types. The results was that significantly more 'hyperactive' type subjects were found among the elderly edentulous who were not wearing dentures (12 of 13) compared with the dentulous young (1 of 14), the elderly dentulous (1 of 13) or the elderly edentulous wearing dentures (1 of 13) (P < 0.001). The tongue-tip motion for the 'hyperactive' type was very complex and the tongue-tip anchoring against the palate was always instable.

Complement fixation by rheumatoid factor.

The capacity for fixation and activation of hemolytic complement by polyclonal IgM rheumatoid factors (RF) isolated from sera of patients with rheumatoid arthritis and monoclonal IgM-RF isolated from the cryoprecipitates of patients with IgM-IgG mixed cryoglobulinemia was examined. RF mixed with aggregated, reduced, and alkylated human IgG (Agg-R/A-IgG) in the fluid phase failed to significantly reduce the level of total hemolytic complement, CH50, or of individual complement components, C1, C2, C3, and C5. However, sheep erythrocytes (SRC) coated with Agg-R/A-IgG or with reduced and alkylated rabbit IgG anti-SRC antibody were hemolyzed by complement in the presence of polyclonal IgM-RF. Human and guinea pig complement worked equally well. The degree of hemolysis was in direct proportion to the hemagglutination titer of the RF against the same coated cells. Monoclonal IgM-RF, normal human IgM, and purified Waldenström macroglobulins without antiglobulin activity were all inert. Hemolysis of coated SRC by RF and complement was inhibited by prior treatment of the complement source with chelating agents, hydrazine, cobra venom factor, specific antisera to C1q, CR, C5, C6, or C8, or by heating at 56 degrees C for 30 min. Purified radiolabeled C4, C3, and C8 included in the complement source were bound to hemolysed SRC in direct proportion to the degree of hemolysis. These data indicate that polyclonal IgM-RF fix and activate complement via the classic pathway. The system described for assessing complement fixation by isolated RF is readily adaptable to use with whole human serum.

T lymphocyte interaction with immunoglobulin G antibody in systemic lupus erythematosus.

Systemic lupus erythematosus (SLE) is an autoimmune disease with multiple immune disturbances whose mechanisms remain unclear. We examined the interaction of antilymphocyte antibodies with cultured normal T lymphocytes. T cells were prepared by E-rosetting after petri-dish removal of adherent cells and cultured for 2-7 d in the presence of SLE sera or normal human sera. Cultured T cells were washed and sonicated, and the amount of cell-associated IgG was quantitated by radioimmunoassay or enzyme-linked immunoassay (ELISA) methods. T cells cultured with 27 of 39 SLE sera showed marked increments of associated immunoglobulin G (IgG) although this was not observed with sera from mixed connective tissue disease patients containing high titers of ribonucleoprotein antibody or normal donors. The effective factors for IgG association in SLE sera were absorbed with normal peripheral blood lymphocytes or T cells. Anti-T cell IgG cytotoxic activity strongly correlated with T cell IgG association (P less than 0.01). T cell-associated IgG was not removed by stripping of cell membrane IgG from living cells by acid buffer treatment; indirect immunofluorescence of cells fixed after 2-4 d of culture revealed cytoplasmic IgG staining. IgG anti-T cell antibodies appeared to associate inside the cell membrane or to penetrate into the cytoplasm of cells. T cell Fc receptor blocking by heat-aggregated IgG or anti-beta 2-microglobulin antibody did not alter IgG cell association. Since pepsin-digested SLE sera showed no T cell association activity, whole IgG antibody molecules appeared to be necessary for interaction with cultured T cells. In addition, reduction and alkylation of active SLE sera completely nullified T cell reactivity. When normal T cells were cultured with SLE sera showing marked IgG T cell association, viability of cultured T cells decreased rapidly after 4 d, which suggests that IgG anti-T cell antibodies were associated with cell destruction. IgG cell-associating antilymphocyte antibodies present in SLE sera may cause T cell disturbances in vivo and may be related to the lymphocytopenia present in SLE patients.