Involvement of autophagy in the maintenance of rat intervertebral disc homeostasis: an in-vitro and in-vivo RNA interference study of Atg5.

OBJECTIVE: In the largest avascular low-nutrient intervertebral disc, resident cells would utilize autophagy, a stress-response survival mechanism by self-digestion and recycling wastes. Our goal was to elucidate the involvement of autophagy in disc homeostasis through RNA interference of autophagy-related gene 5 (Atg5). DESIGN: In vitro, small interfering RNAs (siRNAs) targeting autophagy-essential Atg5 were transfected into rat disc cells. Cell viability with levels of autophagy including Atg5 expression, apoptosis, and senescence was assessed under serum starvation and/or pro-inflammatory interleukin-1 beta (IL-1ß) stimulation. In vivo, time-course autophagic flux was monitored following Alexa Fluor® 555-labeled Atg5-siRNA injection into rat tail discs. Furthermore, 24-h temporary static compression-induced disruption of Atg5 siRNA-injected discs was observed by radiography, histomorphology, and immunofluorescence. RESULTS: In disc cells, three different Atg5 siRNAs consistently suppressed autophagy with Atg5 protein knockdown (mean 44.4% [95% confidence interval: -51.7, -37.1], 51.5% [-80.5, -22.5], 62.3% [-96.6, -28.2]). Then, Atg5 knockdown reduced cell viability through apoptosis and senescence not in serum-supplemented medium (93.6% [-0.8, 21.4]) but in serum-deprived medium (66.4% [-29.8, -8.6]) further with IL-1ß (44.5% [-36.9, -23.5]). In disc tissues, immunofluorescence detected intradiscal signals for the labeled siRNA even at 56-d post-injection. Immunoblotting found 56-d autophagy suppression with prolonged Atg5 knockdown (33.2% [-52.8, -5.3]). With compression, Atg5 siRNA-injected discs presented radiographic height loss ([-43.9, -0.8]), histological damage ([-5.5, -0.2]), and immunofluorescent apoptosis ([2.2, 22.2]) and senescence ([4.1, 19.9]) induction compared to control siRNA-injected discs at 56 d. CONCLUSIONS: This loss-of-function study suggests Atg5-dependent autophagy-mediated anti-apoptosis and anti-senescence. Autophagy could be a molecular therapeutic target for degenerative disc disease.

Human lung microvascular endothelial cells as potential alternatives to human umbilical vein endothelial cells in bio-3D-printed trachea-like structures.

BACKGROUND: We have been trying to produce scaffold-free structures for airway regeneration using a bio-3D-printer with spheroids, to avoid scaffold-associated risks such as infection. Previous studies have shown that human umbilical vein endothelial cells (HUVECs) play an important role in such structures, but HUVECs cannot be isolated from adult humans. The aim of this study was to identify alternatives to HUVECs for use in scaffold-free structures. METHODS: Three types of structure were compared, made of chondrocytes and mesenchymal stem cells with HUVECs, human lung microvascular endothelial cells (HMVEC-Ls), and induced pluripotent stem cell (iPSC)-derived endothelial cells. RESULTS: No significant difference in tensile strength was observed between the three groups. Histologically, some small capillary-like tube formations comprising CD31-positive cells were observed in all groups. The number and diameters of such formations were significantly lower in the iPSC-derived endothelial cell group than in other groups. Glycosaminoglycan content was significantly lower in the iPSC-derived endothelial cell group than in the HUVEC group, while no significant difference was observed between the HUVEC and HMVEC-L groups. CONCLUSIONS: HMVEC-Ls can replace HUVECs as a cell source for scaffold-free trachea-like structures. However, some limitations were associated with iPSC-derived endothelial cells.

Pharmacological inhibition of mTORC1 but not mTORC2 protects against human disc cellular apoptosis, senescence, and extracellular matrix catabolism through Akt and autophagy induction.

OBJECTIVE: The mammalian target of rapamycin (mTOR) is a serine/threonine kinase that integrates nutrients to execute cell growth. We hypothesized that mTOR is influential in the intervertebral disc-largest avascular, low-nutrient organ. Our objective was to identify the optimal mTOR inhibitor for treating human degenerative disc disease. DESIGN: mTOR complex 1 (mTORC1) regulates p70/ribosomal S6 kinase (p70/S6K), negatively regulates autophagy, and is controlled by Akt. Akt is controlled by phosphatidylinositol 3-kinase (PI3K) and mTOR complex 2 (mTORC2). mTORC1 inhibitors-rapamycin, temsirolimus, everolimus, and curcumin, mTORC1&mTORC2 inhibitor-INK-128, PI3K&mTOR inhibitor-NVP-BEZ235, and Akt inhibitor-MK-2206-were applied to human disc nucleus pulposus (NP) cells. mTOR signaling, autophagy, apoptosis, senescence, and matrix metabolism were evaluated. RESULTS: mTORC1 inhibitors decreased p70/S6K but increased Akt phosphorylation, promoted autophagy with light chain 3 (LC3)-II increases and p62/sequestosome 1 (p62/SQSTM1) decreases, and suppressed pro-inflammatory interleukin-1 beta (IL-1ß)-induced apoptotic terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) positivity (versus rapamycin, 95% confidence interval (CI) -0.431 to -0.194; temsirolimus, 95% CI -0.529 to -0.292; everolimus, 95% CI -0.477 to -0.241; curcumin, 95% CI -0.248 to -0.011) and poly (ADP-ribose) polymerase (PARP) and caspase-9 cleavage, senescent senescence-associated beta-galactosidase (SA-ß-gal) positivity (versus rapamycin, 95% CI -0.437 to -0.230; temsirolimus, 95% CI -0.534 to -0.327; everolimus, 95% CI -0.485 to -0.278; curcumin, 95% CI -0.210 to -0.003) and p16/INK4A expression, and catabolic matrix metalloproteinase (MMP) release and activation. Meanwhile, dual mTOR inhibitors decreased p70/S6K and Akt phosphorylation without enhanced autophagy and suppressed apoptosis, senescence, and matrix catabolism. MK-2206 counteracted protective effects of temsirolimus. Additional disc-tissue analysis found relevance of mTOR signaling to degeneration grades. CONCLUSION: mTORC1 inhibitors-notably temsirolimus with an improved water solubility-but not dual mTOR inhibitors protect against inflammation-induced apoptosis, senescence, and matrix catabolism in human disc cells, which depends on Akt and autophagy induction.

Selective interference of mTORC1/RAPTOR protects against human disc cellular apoptosis, senescence, and extracellular matrix catabolism with Akt and autophagy induction.

OBJECTIVE: The mammalian target of rapamycin (mTOR) is a serine/threonine kinase that integrates nutrients to execute cell growth and protein synthesis. We hypothesized that mTOR is essential for the intervertebral disc, the largest avascular, low-nutrient organ. Our objective was to elucidate roles of mTOR signaling in human disc cells. DESIGN: The mTOR exists in two complexes: mTORC1 containing the regulatory-associated protein of mTOR (RAPTOR) and mTORC2 containing the rapamycin-insensitive companion of mTOR (RICTOR). To analyze their functions in human disc nucleus pulposus cells, RNA interference (RNAi) of mTOR targeting mTORC1 and mTORC2, RAPTOR targeting mTORC1, or RICTOR targeting mTORC2 or rapamycin, a pharmacological mTORC1 inhibitor, was applied. First, mTOR signaling including Akt, p70/ribosomal S6 kinase (p70/S6K), and autophagy were assessed. Then, apoptosis, senescence, and matrix metabolism were evaluated under pro-inflammatory interleukin-1 beta (IL-1ß) stimulation. RESULTS: Western blotting showed significant decreases in specific proteins by each RNAi (all P < 0.0001). In mTOR signaling, RNAi of mTOR and RICTOR decreased p70/S6K and Akt phosphorylation, whereas RAPTOR RNAi decreased p70/S6K but increased Akt phosphorylation. All RNAi treatments increased light chain 3 (LC3)-II and decreased p62/sequestosome 1 (p62/SQSTM1), indicating enhanced autophagy. In apoptosis, IL-1ß-induced terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL)-positive cells and poly (ADP-ribose) polymerase (PARP) and caspase-9 cleavage decreased by RAPTOR RNAi. In senescence, IL-1ß-induced senescence-associated beta-galactosidase (SA-ß-gal)-positive cells and p16/INK4A expression also decreased by RAPTOR RNAi. In matrix metabolism, RAPTOR RNAi reduced IL-1ß-induced catabolic matrix metalloproteinase (MMP) release and activation and up-regulated anabolic gene expression. These findings were all consistent with rapamycin administration. Additional disc-tissue analysis detected expression and phosphorylation of mTOR-signaling molecules in varying ages. CONCLUSION: Selective interference of mTORC1/RAPTOR protects against inflammation-induced apoptosis, senescence, and matrix catabolism possibly through Akt and autophagy induction in human disc cells.

Formamidine and cesium-based quasi-two-dimensional perovskites as photovoltaic absorbers.

Formamidine (FA) and cesium (Cs) cations were introduced into quasi-two-dimensional (2D) perovskites as B site cations. The unique crystalline growth of the resulting (n-C6H13NH3)2FAPb2I7, which promotes charge transport in photovoltaic solar cells, was confirmed, as was the stability of this material. The photovoltaic properties of (n-C6H13NH3)2FAPb2I7 were found to be superior to those of other homologous quasi-2D perovskite compounds.

Prognostic value of serum surfactant protein D level prior to transplant for the development of bronchiolitis obliterans syndrome and idiopathic pneumonia syndrome following allogeneic hematopoietic stem cell transplantation.

Bronchiolitis obliterans syndrome (BOS) and idiopathic pneumonia syndrome (IPS) cause high mortality and impaired survival after allogeneic hematopoietic stem-cell transplantation (allo-HSCT). Early recognition of patients at high risk of developing BOS/IPS may lead to improving the outcome of allo-HSCT. We retrospectively analyzed serum surfactant protein A, D (SP-A, -D) and Kerbs von Lungren 6 Ag (KL-6) levels before allo-HSCT in 56 patients who survived more than 90 days after allo-HSCT and compared values of these serum markers and other transplant factors in BOS/IPS patients with those in non-BOS/IPS patients. Five patients developed BOS and two developed IPS at a median interval of 303 and 117 days (range, 100-452 and 95-153) from transplantation. As a result of univariate analysis, pretransplant serum SP-D levels but not SP-A, KL-6 in BOS/IPS patients were significantly lower than those in non-BOS/IPS patients (P=0.03). In multivariate analysis, the patients with lower pretransplant serum SP-D level had a trend toward frequent development of BOS/IPS (P=0.08). Constitutive serum SP-D level before allo-HSCT may be a useful, noninvasive predictor for the development of BOS/IPS.

Primary refractoriness to platelet transfusion caused by Nak(a) antibody alone.

BACKGROUND AND OBJECTIVES: Anti-Nak(a), a platelet-specific antibody, occasionally causes platelet-transfusion refractoriness (PTR) together with human leucocyte antigen (HLA) antibodies. Anti-Nak(a) usually appears after frequent platelet transfusions or pregnancy. We report the first case of PTR caused by anti-Nak(a) alone. MATERIALS AND METHODS: A 19-year-old male patient with testicular tumour showed PTR when receiving his first transfusion of platelets. Screening for platelet antigens and platelet antibodies revealed that he had type I CD36 (Nak(a)) deficiency and that anti-Nak(a), but not anti-HLA, was present before he received his first transfusion. RESULTS: The transfusion of Nak(a)-negative, but HLA non-selected, platelets was effective in raising the platelet count. CONCLUSION: Clinically significant Nak(a) antibody was present as naturally occurring antibody in a platelet glycoprotein IV (CD36)-negative non-transfused male patient.

Virus-associated hemophagocytic syndrome due to rubella virus and varicella-zoster virus dual infection in patient with adult idiopathic thrombocytopenic purpura.

A 26-year-old woman with idiopathic thrombocytopenic purpura (ITP) was admitted to our hospital because of fever and rash. Blood tests revealed thrombocytopenia, liver dysfunction, coagulopathy, and hyperferritinemia. Bone marrow examination revealed many atypical lymphocytes and some histiocytes with hemophagocytosis. On admission she was diagnosed with rubella virus-associated hemophagocytic syndrome (VHAS), but on laboratory examination, she was seropositive for varicella-zoster virus (VZV)-IgM as well as rubella virus-IgM. She was therefore diagnosed with dual infection by rubella virus and VZV. Her simultaneous rubella virus and VZV infection may have been related to the VAHS pathogenesis. She was treated with prednisolone and gamma globulin therapy and recovered completely.

[CD13- and CD33-negative acute myelocytic leukemia (FAB classification; M2) with morphological changes and CD13 expression on recurrence].

A 42-year-old man was diagnosed as having acute myelocytic leukemia in July 1998. The leukemic cells tended to be differentiated, and on the basis of positive peroxidase staining, this case was considered to be AML (M2) according to the FAB classification. t(8;21)(q22;q22) chromosomal abnormality was observed, but surface antigen analysis revealed no expression of either CD13 or CD33, a finding characteristic of myelocytic leukemia. Combination chemotherapy resulted in complete remission, and allogeneic bone marrow transplantation was performed with donor cells from the patient's sister. Unfortunately, however, the patient died about 18 months after the onset of leukemia. Comparison of the findings at recurrence with those at initial diagnosis revealed morphological changes in non-differentiated immature cells (AML-M1) and CD13 surface antigen expression. This was considered to be a rare case of AML with neither CD13 nor CD33 expression at onset, but with CD13 expression at recurrence.

Frustrations in polymer conformation in gels and their minimization through molecular imprinting.

We report an experimental realization of a gel system in which frustrations exist and can be minimized, thus meeting two crucial criteria predicted to enable memory of conformations in polymers. The gels consist of a thermosensitive major monomer component and two minor components. One minor component is positively charged and will form complexes around negatively charged target molecules placed in solution. The complexes can be imprinted into the gel by then cross-linking the second minor component, which will form cross-links additional to those in the major polymer matrix. The complexes are destroyed and reformed upon swelling and reshrinking of the gels, showing that memorization has been achieved.

[Mycosis fungoides terminating in acute myelocytic leukemia].

A 57-year-old woman was admitted to our hospital with suspected leukemia in September 1999. In 1990, systemic erythema had occurred, and mycosis fungoides (MF) had been diagnosed by skin biopsy. Interferon-gamma therapy had not been effective, and the erythema had disappeared after treatment with psoralen and ultraviolet A (PUVA) therapy (1.46 J/cm2). The patient had subsequently done well with a course of topical steroids. On admission this time, the WBC count was 1,600/microliter with 6% blasts. The total nucleated cell count in a bone marrow aspirate was 43.1 x 10(4)/microliter, of which 86.2% were peroxidase-positive blasts. Acute myelocytic leukemia (AML) was diagnosed. Chromosomal analysis demonstrated abnormalities of 48, XX, +4, +8, +add(10)(p11), add(11)(q23) in 10 of 20 cells, and 51, idem, +6, +8, +21, +mar in 8 cells with mixed-lineage leukemia gene rearrangement. Therapies (radiation, chemotherapy and PUVA) for MF, and the altered immune response seen in patients with this disease, especially in the more advanced stages, collectively termed cutaneous T-cell lymphoma (CTCL), suggest that such patients may be at increased risk of a second primary malignancy. To our knowledge, AML has been reported in 8 MF patients including the present one. Attention should be given to the possibility of MF terminating in AML.

Gel catalysts that switch on and off.

We report development of a polymer gel with a catalytic activity that can be switched on and off when the solvent composition is changed. The gel consists of two species of monomers. The major component, N-isopropylacrylamide, makes the gel swell and shrink in response to a change in composition of ethanol/water mixtures. The minor component, vinylimidazole, which is capable of catalysis, is copolymerized into the gel network. The reaction rate for catalytic hydrolysis of p-nitrophenyl caprylate was small when the gel was swollen. In contrast, when the gel was shrunken, the reaction rate increased 5 times. The activity changes discontinuously as a function of solvent composition, thus the catalysis can be switched on and off by an infinitesimal change in solvent composition. The kinetics of catalysis by the gel in the shrunken state is well described by the Michaelis-Menten formula, indicating that the absorption of the substrate by the hydrophobic environment created by the N-isopropylacrylamide polymer in the shrunken gel is responsible for enhancement of catalytic activity. In the swollen state, the rate vs. active site concentration is linear, indicating that the substrate absorption is not a primary factor determining the kinetics. Catalytic activity of the gel is studied for substrates with various alkyl chain lengths; of those studied the switching effect is most pronounced for p-nitrophenyl caprylate.

Disordered expression of inhibitory receptors on the NK1-type natural killer (NK) leukaemic cells from patients with hypersensitivity to mosquito bites.

Recent studies have revealed the existence of a distinct type of NK cell leukaemia of the juvenile type, which presents with hypersensitivity to mosquito bites (HMB) as an essential clinical manifestation and is infected with clonal Epstein-Barr virus (EBV). This disorder is thus called HMB-EBV-NK disease and has been reported in Orientals, mostly from Japan. We investigated the profile of cytokine production and the expression of both types of NK inhibitory receptors, i.e. CD94 lectin-like dimers and killer-cell immunoglobulin-like receptors, in NK leukaemic cells from three patients with HMB-EBV-NK disease. It was found that freshly isolated NK leukaemic cells expressed mRNA for interferon-gamma (IFN-gamma) and additionally produced IL-10 upon stimulation with IL-2, indicating that the NK cells were of NK1 type. More than 98% of NK cells from the patients bore CD94 at a higher level than did normal NK cells, whereas p70 or NKAT2, belonging to immunoglobulin-like receptor, was not expressed in those NK cells. Freshly isolated leukaemic NK cells transcribed mRNA for CD94-associated molecule NKG2C at an abnormally high level, and upon stimulation with IL-2 and/or IL-12 they expressed NKG2A as well. The disordered expression of these inhibitory receptors not only provides some insights into the pathogenesis of HMB-EBV-NK disease but also can be used as phenotypic markers for the diagnosis of this type of NK cell leukaemia.

Reversible molecular adsorption based on multiple-point interaction by shrinkable gels.

A general approach is presented for creating polymer gels that can recognize and capture a target molecule by multiple-point interaction and that can reversibly change their affinity to the target by more than one order of magnitude. The polymers consist of majority monomers that make the gel reversibly swell and shrink and minority monomers that constitute multiple-point adsorption centers for the target molecule. Multiple-point interaction is experimentally proven by power laws found between the affinity and the concentration of the adsorbing monomers within the gels.

Apoptosis and the thymic microenvironment in murine lupus.

The thymus of New Zealand black (NZB) mice undergoes premature involution. In addition, cultured thymic epithelial cells from NZB mice undergo accelerated preprogrammed degeneration. NZB mice also have distinctive and well-defined abnormalities of thymic architecture involving stromal cells, defined by staining with monoclonal antibodies specific for the thymic microenvironment. We took advantage of these findings, as well as our large panel of monoclonal antibodies which recognize thymic stroma, to study the induction of apoptosis in the thymus of murine lupus and including changes of epithelial architecture. We studied NZB, MRL/lpr, BXSB/Yaa, C3H/gld mice and BALB/c and C57BL/6 as control mice. Apoptosis was studied both at basal levels and following induction with either dexamethasone or lipopolysaccharide (LPS). The apoptotic cells were primarily found in the thymic cortex, and the frequency of apoptosis in murine lupus was less than 20% of controls. Moreover, all strains of murine lupus had severe abnormalities of the cortical network. These changes were not accentuated by dexamethasone treatment in cultured thymocytes. However, the thymus in murine lupus was less susceptible to LPS-induced apoptosis than control mice. Finally we note that the number of thymic nurse cells (TNC) was lowest in NZB mice. Our findings demonstrate significant abnormalities in the induction of apoptosis and the formation of TNC-like epithelial cells in SLE mice, and suggest that the abnormalities of the thymic microenvironment have an important role in the pathogenesis of murine lupus.

Thymic microenvironment and NZB mice: the abnormal thymic microenvironment of New Zealand mice correlates with immunopathology.

There are distinct microenvironmental abnormalities of thymic architecture in several murine models of SLE defined using immunohistochemistry and a panel of mAb dissected at thymic epithelial markers. To address the issue of the relationship between the thymic microenvironment and autoimmunity, we studied backcross (NZB x NZW) F1 x NZW mice in which 50% of offspring develop nephritis associated with proteinuria and anti-DNA antibodies. We reasoned that if thymic abnormalities are associated with development of disease, the correlation of abnormalities with lupus-like disease in individual backcross mice will form the foundation for identification of the mechanisms involved. In parallel, we directed a genetic linkage analysis, using markers previously shown to be linked to nephritis and IgG autoantibody production, to determine if such loci were similarly associated with microenvironmental changes. Our data demonstrate that all (NZB x NZW) F1 x NZW backcross mice with disease have microenvironmental defects. Although the microenvironmental defects are not sufficient for development of autoimmune disease, the severity of thymic abnormalities correlates with titers of IgG autoantibodies to DNA and with proteinuria. Consistent with past studies of (NZB x NZW) F1 x NZW mice, genetic markers on proximal chromosome 17 (near MHC) and distal chromosome 4 showed trends for linkage with nephritis. Although the markers chosen only covered about 10-15% of the genome, the results demonstrated trends for linkage with thymic medullary abnormalities for loci on distal chromosome 4 and distal chromosome 1. We believe it will be important to define the biochemical nature of the molecules recognized by these mAbs to understand the relationships between thymic architecture and immunopathology.

Autoantibody production and cytokine profiles of MHC class I (beta2-microglobulin) gene deleted New Zealand black (NZB) mice.

We established a colony of MHC class I deleted (knockout) NZB mice, which lack the beta2 microglobulin gene (NZB.beta2m-/-), to characterize the contribution of MHC class I to the thymic microenvironment abnormalities, autoantibody production and lupus-like disease of NZB mice. Using an extensive panel of well characterized monoclonal antibodies defining thymic epithelial and other stromal elements, we demonstrated that deletion of MHC class I molecules does not change the thymic abnormalities, including the presence of a cortical epithelial cell free region, ectopic expression of medullary epithelial antigens, and the irregular shape of the medullary epithelial network of NZB mice. Moreover, the decreased staining of MTS 33(+) cells, a marker of premature thymocyte maturation, was also seen in NZB.beta2m-/-. However, although NZB.beta2m-/- mice had approximately the same levels of IgM and IgG anti-ss and dsDNA antibodies when compared to control NZB mice, there were significant alterations in the incidence and onset of anti-erythrocyte antibody levels. NZB.beta2m-/- had a lower incidence and a delayed onset of anti-erythrocyte autoantibody production compared to that seen in NZB mice. We also compared constitutive and PHA-P-driven levels of IFN-gamma, IL-4, IL-6, and IL-12 in cells from NZB, NZB.beta-/-2, and control C57BL/6 mice. Mitogen stimulated cells showed a decreased IFN-gamma, and a marked increase in IL-6 and IL-12 in NZB and NZB.beta2m-/- mice.

A comparative analysis of the murine thymic microenvironment in normal, autoimmune, and immunodeficiency states.

It is widely accepted that the thymic microenvironment regulates normal thymopoiesis through a highly coordinated and complex series of cellular and cytokine interactions. A direct corollary of this is that abnormalities within the microenvironment could be of etiologic significance in T-cell-based diseases. Our laboratory has developed a large panel of monoclonal antibodies (mAbs) that react specifically with epithelial or nonepithelial markers in the thymus. We have taken advantage of these reagents to characterize the thymic microenvironment of several genetic strains of mice, including BALB/cJ, C57BL/6J, NZB/BlnJ, SM/J, NOD/Ltz, NOD/Ltz-scid/sz, C57BL/6J-Hcphme/Hcphme, and ALY/NscJcl-aly/aly mice, and littermate control animals. We report herein that control mice, including strains of several backgrounds, have a very consistent phenotypic profile with this panel of monoclonal antibodies, including reactivity with thymic epithelial cells in the cortex, the medulla and the corticomedullary junction, and the extracellular matrix. In contrast, the disease-prone strains studied have unique, abnormal staining of thymic cortex and medulla at both the structural and cellular levels. These phenotypic data suggest that abnormalities in interactions between developing thymocytes and stromal cells characterize disease-prone mice.

The natural history of disease expression in CD4 and CD8 gene-deleted New Zealand black (NZB) mice.

CD4 and CD8 gene-deleted New Zealand black (NZB) mice and, as controls, B6.CD4 -/-, B6.CD8 -/-, NZB, and B6 wild-type (wt) mice were studied for phenotypic and immunologic parameters to determine the contribution of CD4 and CD8 cell lineages in NZB mice. These studies suggest surprisingly that a number of abnormalities are not due to either CD4+ or CD8+ cell lineages but rather are most likely due to non-CD4+ and -CD8+ cell lineages and/or background genes. Such abnormalities include altered thymic architecture, decreased staining of MITS 33+ medullary thymocytes, and an increased frequency of splenic IgM secretory cells. In contrast, deletion of either CD4+ or CD8+ cells appears to differentially influence immunologic function. Deletion of CD8+ cells did not influence titers of spontaneously occurring anti-erythrocyte or anti-DNA autoantibodies. interestingly, 50% of NZB.CD4 -/- mice contained levels of anti-erythrocyte IgG and anti-ssDNA IgM autoantibodies; even without detectable CD4+ cells. Such deletion of CD4+ cells, while leading to marked decreases in the prototype cytokines that characterize Th1 and Th2 subsets in B6 mice, led to a marked increase in IFN-gamma and a moderate increase in IL-4 mRNA levels in NZB.CD4 -/- mice. These data suggest that whereas non-CD4+ and -CD8+ cell lineages and NZB background genes have a marked influence in the development of autoimmune abnormalities, CD4+ cells appear to play a major role in influencing the cytokine environment, whereas CD8+ cells appear to play a minor role.

The murine thymic microenvironment: changes with age.

Immunosenescence has been well described in both human and a variety of animal species and has an important influence on changes in immune function. Although several mechanisms may be operating to explain the alterations in immune function with age, one factor that has attracted significant attention has been the progressive age-dependent involution of the thymus. Hitherto, most studies of thymus have focused only on thymocytes. We have now taken advantage of a well-defined panel of monoclonal antibodies (mAbs called MTS) that recognize and characterize the thymic miroenvironment, including epithelial and nonepithelial elements. Recent data using these MTS mAbs have disclosed significant abnormalities in the thymic cortex in models of murine lupus including the unusual appearance of medullary-type epithelial cells in the cortical areas and the presence of epithelial free spaces or 'cortical holes'. In this study, we investigated age-related changes in the thymic microenvironment in 12-month-old C3H/HeJ, C57BL/6 and BALB/c mice. Controls included thymus from young 4-to 6-week-old mice as well as 6-month-old BALB/c mice. As expected, the thymus of all 12-month-old mice manifested normal and distinctive separation of cortical and medullary epithelium. However, unlike younger mice, the 12-month-old mice had severe changes in these regions. For example, in older mice, the cortex and medulla were diffusely irregular and atrophic and had a poorly defined cortico medullary junction; the former having small disrupted epithelial networks, and the latter containing clusters of atrophic cells. Moreover, the extracellular matrix was increased and contained large irregularly shaped clusters. Interestingly, the thymus of 6-month-old mice expressed some changes within the medullary epithelium and the extracellular matrix, but the cortical epithelium remained unchanged. These age-related degenerative changes in the thymic microenvironment differ significantly from the abnormalities identified in autoimmunity and may be a factor in immunosenescence.