Patterns of glomerulonephritis with crescents: Experience at a tertiary medical center in Saudi Arabia.

A series of 78 cases of glomerulonephritis (GN), in which renal biopsy revealed changes of GN associated with crescent formation, were reviewed. Renal pathology findings were correlated with clinical features including patient's age, renal function, and serologic findings. In most of the cases (71.8%), the crescents were due to immune complex-mediated GN. This was followed by pauci-immune GN (20.5%) and anti-glomerular basement membrane antibody (GBM) GN (7.7%). The percentage of glomeruli with crescents was the highest in cases of anti-GBM disease (mean of 93.3%), followed by pauci-immune GBM (mean of 48.2%) and immune complex GN (30.9%). In cases with the pauci- immune GN, there were additional features of glomerular injury including fibrinoid necrosis, disruption of the GBM, and rupture of Bowman's capsule. These changes were generally more pronounced in a subset of pauci-immune GN associated with serum elevation of antineutrophil cytoplasmic antibody (c-ANCA). In biopsies from patient with immune complex disease, systemic lupus erythematosus was the most common cause of crescentic GN.

Vanillic Acid Ameliorates Cationic Bovine Serum Albumin Induced Immune Complex Glomerulonephritis in BALB/c Mice.

Preclinical Research Vanillic acid (VA) is a dihydroxybenzoic acid derivative widely used as a flavoring agent. It has chemopreventive effects on experimentally-induced carcinogenesis and in ulcerative colitis. The object of the present study was to investigate the effects of VA, alone and in combination with methylprednisolone (MP), on cationic bovine serum albumin (cBSA induced immune-complex glomerulonephritis in female BALB/c mice. Pre-immunization was carried out with cBSA in BALB/c mice and repeated (cBSA, 13 mg/kg, 3 times/week, i.v.) for 6 weeks to induce glomerulonephritis which was confirmed by the presence of severe proteinuria. The effect of VA (50, 100, and 200 mg/kg, p.o.) and its combination with MP (12.5 mg/kg, p.o.) was assessed in the nephrotic disease model. Treatment with VA decreased inflammatory nephrotic injury as evidenced by decreased proteinuria, serum creatinine, blood urea nitrogen, serum IgG1 and TNF-α levels. Co-administration of VA with MP showed an improvement in the immunohistochemistry of glomerular nephrin and podocin. The present results indicate that VA has a nephroprotective effect in the management of autoimmune nephritis. Drug Dev Res 77 : 171-179, 2016. © 2016 Wiley Periodicals, Inc.

Neutrophils Self-Regulate Immune Complex-Mediated Cutaneous Inflammation through CXCL2.

Deposition of immune complexes (ICs) in tissues triggers acute inflammatory pathology characterized by massive neutrophil influx leading to edema and hemorrhage, and is especially associated with vasculitis of the skin, but the mechanisms that regulate this type III hypersensitivity process remain poorly understood. Here, using a combination of multiphoton intravital microscopy and genomic approaches, we re-examined the cutaneous reverse passive Arthus reaction and observed that IC-activated neutrophils underwent transmigration, triggered further IC formation, and transported these ICs into the interstitium, whereas neutrophil depletion drastically reduced IC formation and ameliorated vascular leakage in vivo. Thereafter, we show that these neutrophils expressed high levels of CXCL2, which further amplified neutrophil recruitment and activation in an autocrine and/or paracrine manner. Notably, CXCL1 expression was restricted to tissue-resident cell types, but IC-activated neutrophils may also indirectly, via soluble factors, modulate macrophage CXCL1 expression. Consistent with their distinct cellular origins and localization, only neutralization of CXCL2 but not CXCL1 in the interstitium effectively reduced neutrophil recruitment. In summary, our study establishes that neutrophils are able to self-regulate their own recruitment and responses during IC-mediated inflammation through a CXCL2-driven feed forward loop.

[Pathophysiology of urticaria]. / Physiopathologie de l'urticaire.

Urticaria is a dermal edema resulting from vascular dilatation and leakage of fluid into the skin in response to molecules released from mast cells. The major mediator responsible for urticaria is histamine. However, the clinical spectrum and pattern of lesions indicate that other molecules, including prostaglandins, leukotrienes, cytokines, and chemokines, produced at different times after mast cell activation contribute to the polymorphism of this symptom and the variable evolution of this disease. It is a common practice to distinguish immunological and nonimmunological urticaria. Immunological urticaria is a hypersensitivity reaction mediated by antibodies and/or T-cells that results in mast cell activation. Although immunoglobulin (Ig) E-mediated type I hypersensitivity (HS) was long postulated to be the major immunological pathway associated with mast cell activation, interaction between IgEbound mast cells and allergens is unlikely to be the mechanism by which urticaria develops in most patients. It is now well established that urticaria may result from the binding of IgG auto-antibodies to IgE and/or to the receptor for IgE molecules on mast cells, thus corresponding to a type II HS reaction. These auto-immune urticarias represent up to 50 % of patients with chronic urticaria. Mast cell activation can also result from type III HS through the binding of circulating immune complexes to mast cell-expressing Fc receptors for IgG and IgM. Finally, under certain circumstances, T-cells can induce activation of mast cells, as well as histamine release (type IV HS). Nonimmunological urticarias result from mast cell activation through membrane receptors involved in innate immunity (e.g., complement, Toll-like, cytokine/chemokine, opioid) or by direct toxicity of xenobiotics (haptens, drugs). In conclusion, urticaria may result from different pathophysiological mechanisms that explain the great heterogeneity of clinical symptoms and the variable responses to treatment.

A case of lupus-like glomerulonephritis in an HIV patient with nephrotic range proteinuria, purpura, and elevated IgA level.

Human immunodeficiency virus (HIV) infection is growing medical concern worldwide. There are many types of glomerulonephritis which are associated with HIV infection. We report a case of a 53-year-old Korean man with an HIV infection, who was developed nephritic range proteinuria and purpura with elevated IgA level rasing a possibility of Henoch-Schölein Purpura (H-S purpura). However, renal biopsy showed "lupus-like feature" glomerulonephritis without clinical or serologic evidence of systemic lupus erythematosus. Although baseline renal function was maintained without further need for maintenance dialysis following anti-retroviral therapy (ART) and steroid, patient died from uncontrolled gastrointestinal bleeding.

The NLRP3/ASC inflammasome promotes T-cell-dependent immune complex glomerulonephritis by canonical and noncanonical mechanisms.

Interleukin (IL)-1ß contributes to renal injury in immune complex glomerulonephritis. However, production of mature IL-1ß depends on activation of the inflammasome that cleaves pro-IL-1ß into its secretable form. A functional role of the NLRP3-containing inflammasome, which responds to various endogenous danger signals, was found in tubulointerstitial nephropathies, but its function in glomerular disease has not been established. To determine whether NLRP3 and its adapter molecule ASC contribute to glomerulonephritis, we induced T-cell-dependent autologous nephrotoxic serum nephritis in Nlrp3- and Asc-deficient mice. Renal expression of NLRP3/ASC inflammasome components and pro-IL-1ß increased during nephrotoxic serum nephritis and was abundant in renal dendritic cells. This was associated with renal production of mature IL-1ß, indicating inflammasome activation. Nlrp3 and Asc deficiency significantly attenuated glomerular injury, renal leukocyte infiltration, and T-cell activation. Production of mature IL-1ß was abrogated in Asc-deficient mice, consistent with a loss of inflammasome-dependent IL-1ß activation. Surprisingly, renal IL-1ß secretion remained intact in Nlrp3-deficient mice, indicating noncanonical pro-inflammatory effects of NLRP3 in autologous nephrotoxic serum nephritis. This may include NLRP3-mediated glomerular release of pro-inflammatory high-mobility group box 1 protein as a noncanonical function of NLRP3/ASC in glomerulonephritis. Thus, therapeutic blockade of the NLRP3/ASC/IL-1ß axis may be beneficial in glomerulonephritis.

Comparison of risk factors and outcomes in HIV immune complex kidney disease and HIV-associated nephropathy.

BACKGROUND AND OBJECTIVES: HIV-associated nephropathy (HIVAN) is well described, but the clinical features of a group of renal pathologies characterized by Ig or immune complex depositions referred to as HIV-associated immune complex kidney disease (HIVICK) have not been well established. The objective of this study is to assess risk factors for HIVICK compared with contemporaneous control participants. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS: A nested case-control study of 751 HIV-infected patients followed from January 1996 to June 2010 was conducted. Groups were compared using the chi-squared test or rank-sum analysis. Conditional logistic regression was used to estimate odds ratios (ORs) for HIVICK. Incidences of overall ESRD and with/without combined antiretroviral therapy (cART) exposure were calculated. RESULTS: HIVICK patients were predominantly African American (92%). Compared with matched controls, patients with HIVICK were more likely to have HIV RNA >400 copies/ml (OR, 2.5; 95% confidence interval [95% CI], 1.2 to 5.2), diabetes (OR, 2.8; 95% CI, 1.1 to 6.8), and hypertension (OR, 2.3; 95% CI, 1.2 to 4.5). Compared with HIVAN, patients with HIVICK had more antiretroviral therapy exposure, lower HIV viral loads, and higher CD4 and estimated GFR. ESRD was less common in the HIVICK versus the HIVAN group (30% versus 82%; P<0.001), and the use of cART was not associated with ESRD in HIVICK patients (25% versus 26; P=0.39). CONCLUSIONS: HIVICK was predominantly observed in African-American patients and associated with advanced HIV disease. ESRD incidence is lower in HIVICK patients compared with those with HIVAN. Unlike HIVAN, cART use was not associated with the incidence of ESRD in HIVICK.

Glomerular antibodies in lupus nephritis.

Lupus nephritis (LN) remains the most common severe manifestation of systemic lupus erythematosus (SLE) characterized by the presence of autoantibodies (Abs) that are believed to play a central role in the pathogenesis of LN. Among more than 100 Abs reported in SLE, only a few display a direct glomerular binding capacity. Such antiglomerular Abs are detected at the onset of the disease before antinuclear Abs detection and proteinuria, this detection is associated with the related autoantigen overexpression. Antiglomerular Abs are able to interfere with cell metabolism, to penetrate living cells, and to induce glomerular cell proliferation. In addition, antiglomerular Abs could be nephritogenic causing proteinuria, particularly when they cross-react with anti-dsDNA Abs. Antiglomerular Abs encompass anti-α-actinin, anti-laminin-1, antifibronectin, antimyosin, and anticollagen Abs. The pathogenic activity of anti-α-actinin Abs has been demonstrated in non-autoimmune mice after immunization with α-actinin, but not with dsDNA, leading to a SLE-like disease with proteinuria and glomerular immune complex deposition. Similarly, extracorporeal immunoabsorption to remove anti-laminin-1 Abs reduces kidney-Abs deposition and proteinuria in mice and humans proving their pathogenic effect. Altogether this suggests that antiglomerular Abs participate, at least at the beginning, in the glomerular immune complex deposition and in the kidney damage.

Pulmón del cuidador de palomas / Pigeon breeder's lung

El pulmón del cuidador de palomas es una neumonitis por hipersensibilidad poco frecuente en pediatría, que se desarrolla por inhalación de proteínas derivadas de las palomas. Presentamos un caso de pulmón de cuidador de palomas en un niño de 12 años. Refería tos seca de 15 días de evolución, disnea y pérdida de peso. A la exploración física, destacaba cianosis, tiraje intercostal y supraclavicular, taquipnea, subcrepitantes a la auscultación respiratoria y saturación de oxígeno del 91% a FiO2 ambiente. En la analítica de sangre destacaba hipergammaglobulinemia y aumento de lactato deshidrogenasa. Las pruebas funcionales respiratorias mostraron un patrón mixto con disminución de la difusión de monóxido de carbono (DLCO). Los hallazgos radiológicos fueron compatibles con el diagnóstico de neumonitis por hipersensibilidad y los anticuerpos de inmunoglobulina G a palomas (método ELISA) y los tests cutáneos con suero de paloma fueron positivos. El niño presentó una buena respuesta al tratamiento corticoideo y a la evitación del antígeno (AU)

Bird fancier’s or breeder’s lung is an unusual hypersensitivity pneumonitis found in pediatric patients, due to avian antigen inhalation. A case of pigeon breeder’s lung in a 12 years old child is presented. Clinical symptoms were dry cough for 15 days, dyspnea and weight loss. Physical examination of the patient showed cyanosis, chest tightness, tachypnea, inspiratory crackles and oxygen saturation of 91% in room air. Laboratory data revealed hypergammaglobulinemia and elevated LDH. Pulmonary function testing showed a mixed ventilatory pattern and a decreased carbon monoxide diffusion (DLCO) capacity. Radiological findings were compatible with hypersensitivity pneumonitis, and pigeon IgG antibodies (ELISA) and skin tests with pigeon serum were positive. The child improved with corticoid therapy and antigen avoidance (AU)

Does damage cause inflammation? Revisiting the link between joint damage and inflammation.

Rheumatoid arthritis (RA) is characterised by both inflammation, as manifested by pain and swelling, and destruction of the joints. Unequivocal evidence indicates that disease activity, and thus the inflammatory response, is linked to joint damage. From this viewpoint we suggest that, vice versa, joint damage might be a cause of the active disease process, thus leading to a vicious cycle of events. The background to this notion stems from the known autoimmune response in RA, the potential of cartilage and bone breakdown products to elicit inflammation and notions that in joints that have undergone surgery with cartilage removal RA does not flare. However, the clinical evidence for this relationship is still to be provided as proof of the concept.

Glomerulopatías asociadas a la infección por VIH una perspectiva española / Glomerulopathies associated to HIV infection: a spanish perspective

La nefropatía asociada al VIH (HIVAN) es la causa más común de insuficiencia renal crónica en los pacientes VIH de raza negra. Sin embargo, en los últimos años la prevalencia de otras glomerulopatías asociadas a inmunocomplejos ha ido en aumento. Nuestro estudio describe la patología glomerular en los pacientes VIH de nuestro centro. Material y métodos: estudio retrospectivo de pacientes VIH con afectación glomerular confirmada mediante biopsia renal. Resultados: Se detectaron 27 pacientes en los que se habían diagnosticado las siguientes glomerulopatías: glomerulonefritis membranoproliferativa (GNMP) en 8, glomeruloesclerosis focal y segmentaria no colapsante (GSF) en 7, nefropatía mesangial IgA (GNIgA) en 6, glomeruloesclerosis colapsante (HIVAN) en 4 y glomerulonefritis membranosa (GNM) en 2. La mayoría de los casos eran varones jóvenes de raza blanca. Destaca una alta coinfección con el virus de la hepatitis C (VHC) (77,8%) y con el virus de la hepatitis B (VHB) (37%). En el momento del diagnóstico la mayoría de los pacientes presentaba proteinuria (96%), con síndrome nefrótico en el 52% de los casos, y un 59% presentaba un deterioro agudo de la función renal. Nueve pacientes (33%) presentaron HTA maligna al diagnóstico, siendo particularmente frecuente esta complicación entre los pacientes con GNIgA (4/6, 66%). Conclusiones: las glomerulopatías más frecuentes en nuestra población VIH son las asociadas a inmunocomplejos, sobre todo la GNMP asociada a la infección por el VHC. La HTA maligna tiene una alta incidencia en los pacientes VIH, más marcada en los pacientes con nefropatía mesangial IgA

HIV nephropathy (HIVAN) is the most frequent cause of chronic renal failure in HIV-infected black patients. However, the prevalence of other glomerulopathies mediated by immunocomplexes has increased in the last years. We report on the glomerular diseases observed in HIV patients in our Hospital. Methods: A retrospective study of all patients with HIV infection and glomerular diseases diagnosed by renal biopsy. Results: We found 27 patients with the following glomerular diseases: membranoproliferative glomerulonephritis (MPGN) in 8 patients, non-collapsing focal segmental glomerulosclerosis (FSGS) in 7, IgA nephropaty (IgA N) in 6, collapsing glomerulosclerosis in 4 (HIVAN, and membranous nephropaty (MN) in 2. Most of patients were young white men. A high prevalence of coinfection with hepatitis C virus (HCV) (77.8%) and hepatitis B virus (HBV) (37%) was found. At diagnosis, most of patients (90%) had proteinuria, with nephrotic syndrome in 52% of them; 59% presented with acute renal failure. Nine patients (33%) showed malignant hypertension at diagnosis: this complication was particularly common among IgA N patients (4/6, 66%).Conclusion: In our Hospital, immunocomplex-mediated glomerulonephritis were more frequent than HIVAN among HIV-infected patients. HCV-associated MPGN was the most frequently detected glomerular disease. A high prevalence of malignant hypertension was observed at diagnosis, particularly among patients with IgAN

Falsa determinación de troponina T en el contexto de enfermedades inmunológicas / Erroneus troponin T determination in immune diseases

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Activating and inhibitory IgG Fc receptors on human DCs mediate opposing functions.

Human monocyte-derived DCs (moDCs) and circulating conventional DCs coexpress activating (CD32a) and inhibitory (CD32b) isoforms of IgG Fcgamma receptor (FcgammaR) II (CD32). The balance between these divergent receptors establishes a threshold of DC activation and enables immune complexes to mediate opposing effects on DC maturation and function. IFN-gamma most potently favors CD32a expression on immature DCs, whereas soluble antiinflammatory concentrations of monomeric IgG have the opposite effect. Ligation of CD32a leads to DC maturation, increased stimulation of allogeneic T cells, and enhanced secretion of inflammatory cytokines, with the exception of IL-12p70. Coligation of CD32b limits activation through CD32a and hence reduces the immunogenicity of moDCs even for a strong stimulus like alloantigen. Targeting CD32b alone does not mature or activate DCs but rather maintains an immature state. Coexpression of activating and inhibitory FcgammaRs by DCs reveals a homeostatic checkpoint for inducing tolerance or immunity by immune complexes. These findings have important implications for understanding the pathophysiology of immune complex diseases and for optimizing the efficacy of therapeutic mAbs. The data also suggest novel strategies for targeting antigens to the activating or inhibitory FcgammaRs on human DCs to generate either antigen-specific immunity or tolerance.

Autoimmunity and glomerulonephritis in mice with targeted deletion of the serum amyloid P component gene: SAP deficiency or strain combination?

Human serum amyloid P component (SAP) binds avidly to DNA, chromatin and apoptotic cells in vitro and in vivo. 129/Sv x C57BL/6 mice with targeted deletion of the SAP gene spontaneously develop antinuclear autoantibodies and immune complex glomerulonephritis. SAP-deficient animals, created by backcrossing the 129/Sv SAP gene deletion into pure line C57BL/6 mice and studied here for the first time, also spontaneously developed broad spectrum antinuclear autoimmunity and proliferative immune complex glomerulonephritis but without proteinuria, renal failure, or increased morbidity or mortality. Mice hemizygous for the SAP gene deletion had an intermediate autoimmune phenotype. Injected apoptotic cells and isolated chromatin were more immunogenic in SAP(-/-) mice than in wild-type mice. In contrast, SAP-deficient pure line 129/Sv mice did not produce significant autoantibodies either spontaneously or when immunized with extrinsic chromatin or apoptotic cells, indicating that loss of tolerance is markedly strain dependent. However, SAP deficiency in C57BL/6 mice only marginally affected plasma clearance of exogenous chromatin and had no effect on distribution of exogenous nucleosomes between the liver and kidneys, which were the only tissue sites of catabolism. Furthermore, transgenic expression of human SAP in the C57BL/6 SAP knockout mice did not abrogate the autoimmune phenotype. This may reflect the different binding affinities of mouse and human SAP for nuclear autoantigens and/or the heterologous nature of transgenic human SAP in the mouse. Alternatively, the autoimmunity may be independent of SAP deficiency and caused by expression of 129/Sv chromosome 1 genes in the C57BL/6 background.

A study of leprosy reactions in a tertiary hospital in Delhi.

A retrospective study of 531 leprosy patients was undertaken to study the profile of reactions in the post Multi-Drug-Therapy period in a tertiary hospital in Delhi. BT was the most common group. The prevalence of reactions was found to be 8.09% for the Type 1 and 4.70% for the Type 2 reactions for a male:female ratio of 2.2. The Type 1 reaction was most frequently observed in the BB group followed by BL, BT and LL groups respectively. More than half of the patients had reactions at the time of presentation. In only 39.8% of the patients did reaction follow Multi-Drug-Therapy. In 4.5% of the patients with Type 1 reactions (T1R), concomitant infections were noted. The most common presentation of T1R was cutaneous lesions (74.41%) followed by cutaneous lesions and neuritis (53.6%), neuritis alone (12.1%), and only edema of hands and feet (7.31%) respectively. The Type 2 reactions (T2R) presented chiefly as papulo-nodular (92%) lesions followed by pustulonecrotic (8%) lesions. Associated neuritis was found in 40% and periosteitis and iritis in 8% and 4%, respectively. In 8.6% of the patients with T2R, precipitating factors could be observed. The prevalence of deformities in patients with reaction was 25%, and was more common in females. Deformities were observed in 23.25% of the T1R patients and 28% of the T2R patients.

Bacterial CpG-DNA aggravates immune complex glomerulonephritis: role of TLR9-mediated expression of chemokines and chemokine receptors.

Immune complex glomerulonephritis (GN) often deteriorates during infection with viruses and bacteria that, in contrast to mammals, have DNA that contains many unmethylated CpG motifs. Balb/c mice with horse apoferritin-induced GN (HAF-GN) were treated with either saline, CpG-oligodeoxynucleotides (ODN), or control GpC-ODN. Only CpG-ODN exacerbated HAF-GN with an increase of glomerular macrophages, which was associated with massive albuminuria and increased renal MCP-1/CCL2, RANTES/CCL5, CCR1, CCR2, and CCR5 mRNA expression. CpG-ODN induced a Th1 response as indicated by serum anti-HAF IgG(2a) titers, mesangial IgG(2a) deposits, and splenocyte IFN-gamma secretion. Messenger RNA for the CpG-DNA receptor Toll-like reeptor 9 (TLR9) was present in kidneys with HAF-GN but not in normal kidneys. The source of TLR9 mRNA in HAF-GN could be infiltrating macrophages or intrinsic renal cells, e.g., mesangial cells; but, in vitro, only murine J774 macrophages expressed TLR9. In J774 cells, CpG-ODN induced the chemokines MCP-1/CCL2 and RANTES/CCL5 and the chemokine receptors CCR1 and CCR5. It is concluded that CpG-DNA can aggravate preexisting GN via a shift toward a Th1 response but also by a novel pathway involving TLR9-mediated chemokine and chemokine receptor expression by macrophages, which may contribute to the enhanced glomerular macrophage recruitment and activation. This mechanism may be relevant during infection-triggered exacerbation of human immune-complex GN and other immune-mediated diseases in general.

Gell and Coombs's classification: is it still valid?

The Gell and Coombs's classification divides drug allergies into four pathophysiological types, namely anaphylaxis (type I), antibody-mediated cytotoxic reactions (type II), immune complex-mediated reactions (type III), and delayed type hypersensitivity (type IV). Although this classification was proposed more than 30 years ago, it is still widely used. As only a limited number of drug allergies fit into this classification which does not include our current understanding of the immune response, its use is not recommended, particularly in the context of the preclinical safety evaluation of new therapeutic agents. In fact, three different situations can be identified, namely pseudo-allergic reactions, primarily antibody-mediated reactions and cell-mediated reactions, which could serve as a basis for modern and more adequate classifications

Synergistic enhancement of chemokine generation and lung injury by C5a or the membrane attack complex of complement.

Complement plays an important role in many acute inflammatory responses. In the current studies it was demonstrated that, in the presence of either C5a or sublytic forms of the complement-derived membrane attack complex (MAC), rat alveolar macrophages costimulated with IgG immune complexes demonstrated synergistic production of C-X-C (macrophage inflammatory protein-2 and cytokine-induced neutrophil chemoattractant) and C-C (macrophage inflammatory protein-1alpha and monocyte chemoattractant-1) chemokines. In the absence of the costimulus, C5a or MAC did not induce chemokine generation. In in vivo studies, C5a and MAC alone caused limited or no intrapulmonary generation of chemokines, but in the presence of a costimulus (IgG immune complexes) C5a and MAC caused synergistic intrapulmonary generation of C-X-C and C-C chemokines but not of tumor necrosis factor alpha. Under these conditions increased neutrophil accumulation occurred, as did lung injury. These observations suggest that C5a and MAC function synergistically with a costimulus to enhance chemokine generation and the intensity of the lung inflammatory response.

Apoptosis and Fas/Fas ligand mRNA expression in acute immune complex alveolitis in mice.

Deoxyribonucleic acid (DNA) strand breaks as a characteristic of apoptosis, and Fas antigen (Fas)/Fas ligand (FasL) expression may participate in acute immune complex alveolitis in mice. Male Institute for Cancer Research (ICR) mice were injected intravenously with immunoglobulin G (IgG) antibodies against ovalbumin and inhaled an aerosolized oval albumin (OA) solution. They were killed at 4, 6, 12, 24, 48 h and 7 days after aerosolization. We assessed DNA fragmentation by agarose gel electrophoresis and terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate biotin nick end-labelling (TUNEL). The expression of Fas and FasL messenger ribonucleic acid (mRNA) in lung tissues was assessed by reverse transcriptase (RT) polymerase chain reaction, and by in situ hybridization (ISH) to localize Fas mRNA, and RT in situ polymerase chain reaction to localize FasL mRNA. The fragmentation of DNA extracted from lung tissue was found 6-24 h after OA inhalation. TUNEL detected positive signals in bronchial and alveolar epithelial, endothelial and inflammatory cells in the lung tissue. These positive signals had disappeared 7 days after OA inhalation. TUNEL also detected positive signals in apoptotic neutrophils in bronchoalveolar lavage fluid at 6-12 h. Fas mRNA was expressed in the alveolar epithelial and inflammatory cells, while the expression of FasL mRNA appeared to be upregulated in infiltrating inflammatory cells at 6-24 h. These results suggest that apoptosis may be associated with the resolution of inflammation and with tissue repair and also suggest the involvement of the Fas antigen/Fas ligand pathway in acute immune complex alveolitis in mice.