[Results of dacryocystorhinostomy according to Toti from 2000 to 2012]. / Ergebnisse der Dacryozystorhinostomie nach Toti im Zeitraum von 2000 bis 2012.

BACKGROUND: The aim of this study was to describe the efficiency, long-term success, patient satisfaction and recurrence rate after dacryocystorhinostomy according to Toti in a retrospective analysis. MATERIAL AND METHODS: At the Eye Clinic of the Paracelsus Medical University Salzburg 188 eyes of 176 patients with stenosis/obstruction of lacrimal duct were surgically treated between January 2000 and December 2012. Of these patients 173 eyes had no surgery before DCR according to Toti and 15 eyes had already been operated with diverse dacryocystorhinostomies. All patients underwent dacryocystorhinostomy according to Toti. Pre- and postoperative clinical finings were analysed retrospectively. Postoperative long-term results regarding patient satisfaction, absence of inflammation, epiphora and annoyance through local scar building had been evaluated with a questionnaire in a cross-sectional analysis. RESULTS: The primary success rate of DCR according to Toti was 91,9 % and the secondary success rate 98,3 % in patients without surgery preoperatively. Classifying by localisation of stenosis, better results could be reached in patients with postsaccal stenosis/obstructions (94,3 %) than in those with presaccal obstructions (77,8 %) or with mixed pre- and postsaccal stenosis/obstructions (86,7 %). Also in the patient group with previous surgery primary and secondary success rates of 93,3 % could be achieved after DCR according to Toti. CONCLUSIONS: This study confirms that DCR according to Toti is a highly successful technique minimising epiphora and discomfort. The best success rate was found in patients with postsaccal stenosis/obstructions. The local scar was not found to be disturbing.

A novel, microscope based, non-invasive laser Doppler flowmeter for choroidal blood flow assessment.

Impaired ocular blood flow is involved in the pathogenesis of numerous ocular diseases like glaucoma or AMD. The purpose of the present study was to introduce and validate a novel, microscope based, non-invasive Laser Doppler Flowmeter (NI-LDF) for measurement of blood flow in the choroid. The custom made NI-LDF was compared with a commercial fiber optic based laser Doppler flowmeter (Perimed PF4000). Linearity and stability of the NI-LDF were assessed in a silastic tubing model (i.d. 0.3 mm) at different flow rates (range 0.4-3 ml/h). In a rabbit model continuous choroidal blood flow measurements were performed with both instruments simultaneously. During blood flow measurements ocular perfusion pressure was changed by manipulations of intraocular pressure via intravitreal saline infusions. The NI-LDF measurement correlated linearly to intraluminal flow rates in the perfused tubing model (r = 0.99, p < 0.05) and remained stable during a 1 h measurement at a constant flow rate. Rabbit choroidal blood flow measured by the PF4000 and the NI-LDF linearly correlated with each other over the entire measurement range (r = 0.99, y = x∗1.01-12.35 P.U., p < 0.001). In conclusion, the NI-LDF provides valid, semi quantitative measurements of capillary blood flow in comparison to an established LDF instrument and is suitable for measurements at the posterior pole of the eye.

Iron Rims in Patients With Multiple Sclerosis as Neurodegenerative Marker? A 7-Tesla Magnetic Resonance Study.

Introduction: Multiple sclerosis (MS) is a demyelinating and neurodegenerative disease of the central nervous system, characterized by inflammatory-driven demyelination. Symptoms in MS manifest as both physical and neuropsychological deficits. With time, inflammation is accompanied by neurodegeneration, indicated by brain volume loss on an MRI. Here, we combined clinical, imaging, and serum biomarkers in patients with iron rim lesions (IRLs), which lead to severe tissue destruction and thus contribute to the accumulation of clinical disability. Objectives: Subcortical atrophy and ventricular enlargement using an automatic segmentation pipeline for 7 Tesla (T) MRI, serum neurofilament light chain (sNfL) levels, and neuropsychological performance in patients with MS with IRLs and non-IRLs were assessed. Methods: In total 29 patients with MS [15 women, 24 relapsing-remitting multiple sclerosis (RRMS), and five secondary-progressive multiple sclerosis (SPMS)] aged 38 (22-69) years with an Expanded Disability Status Score of 2 (0-8) and a disease duration of 11 (5-40) years underwent neurological and neuropsychological examinations. Volumes of lesions, subcortical structures, and lateral ventricles on 7-T MRI (SWI, FLAIR, and MP2RAGE, 3D Segmentation Software) and sNfL concentrations using the Simoa SR-X Analyzer in IRL and non-IRL patients were assessed. Results: (1) Iron rim lesions patients had a higher FLAIR lesion count (p = 0.047). Patients with higher MP2Rage lesion volume exhibited more IRLs (p <0.014) and showed poorer performance in the information processing speed tested within 1 year using the Symbol Digit Modalities Test (SDMT) (p <0.047). (2) Within 3 years, patients showed atrophy of the thalamus (p = 0.021) and putamen (p = 0.043) and enlargement of the lateral ventricles (p = 0.012). At baseline and after 3 years, thalamic volumes were lower in IRLs than in non-IRL patients (p = 0.045). (3) At baseline, IRL patients had higher sNfL concentrations (p = 0.028). Higher sNfL concentrations were associated with poorer SDMT (p = 0.004), regardless of IRL presence. (4) IRL and non-IRL patients showed no significant difference in the neuropsychological performance within 1 year. Conclusions: Compared with non-IRL patients, IRL patients had higher FLAIR lesion counts, smaller thalamic volumes, and higher sNfL concentrations. Our pilot study combines IRL and sNfL, two biomarkers considered indicative for neurodegenerative processes. Our preliminary data underscore the reported destructive nature of IRLs.

High-field, high-resolution, susceptibility-weighted magnetic resonance imaging: improved image quality by addition of contrast agent and higher field strength in patients with brain tumors.

INTRODUCTION: To demonstrate intratumoral susceptibility effects in malignant brain tumors and to assess visualization of susceptibility effects before and after administration of the paramagnetic contrast agent MultiHance (gadobenate dimeglumine; Bracco Imaging), an agent known to have high relaxivity, with respect to susceptibility effects, image quality, and reduction of scan time. METHODS: Included in the study were 19 patients with malignant brain tumors who underwent high-resolution, susceptibility-weighted (SW) MR imaging at 3 T before and after administration of contrast agent. In all patients, Multihance was administered intravenously as a bolus (0.1 mmol/kg body weight). MR images were individually evaluated by two radiologists with previous experience in the evaluation of pre- and postcontrast 3-T SW MR images with respect to susceptibility effects, image quality, and reduction of scan time. RESULTS: In the 19 patients 21 tumors were diagnosed, of which 18 demonstrated intralesional susceptibility effects both in pre- and postcontrast SW images, and 19 demonstrated contrast enhancement in both SW images and T1-weighted spin-echo MR images. Conspicuity of susceptibility effects and image quality were improved in postcontrast images compared with precontrast images and the scan time was also reduced due to decreased TE values from 9 min (precontrast) to 7 min (postcontrast). CONCLUSION: The intravenous administration of MultiHance, an agent with high relaxivity, allowed a reduction of scan time from 9 min to 7 min while preserving excellent susceptibility effects and image quality in SW images obtained at 3 T. Contrast enhancement and intralesional susceptibility effects can be assessed in one sequence.

The projected increase in glaucoma due to the aging population in Austria from 2001 to 2031: results based on data of the Salzburg-Moorfields Collaborative Glaucoma Study.

PURPOSE: The aim of this study is to present the projected increase in definite primary open angle glaucoma (POAG) and related diseases in Austria from 2001 to 2031. METHODS: The present work is based on two data sources: population projections in Austria and detection rates of the Salzburg-Moorfields Collaborative Glaucoma Study for Austrians in the age groups 40-54 years, 55-69 years, and 70 years and above. The estimates of this glaucoma screening program are based on a total of 3419 subjects. Sensitivity analyses were applied to test the effects of higher and lower sets of prevalence assumptions on the extent of the probable projections. RESULTS: The number of Austrians with definite POAG, early POAG, POAG suspects, and ocular hypertension (OHT) is expected to increase until 2031 by 0.5%, 43.1%, and 65.6% in the three age groups specified above, respectively. The overall number of Austrians with POAG at the age of 40 or older is estimated to increase from 67,600 in 2001 to 96,400 in 2031. This corresponds to an increase of 42% from 2001 to 2031 (lower scenario: 37%, upper scenario: 47%). Similar increases are expected for individuals with early POAG, POAG suspects, and OHT. CONCLUSIONS: These projections provide an objective basis to estimate the resources that may be needed by health authorities and care providers such as ophthalmologists in the future and should help to design glaucoma blindness prevention programs or screening studies in Austria. The predicted continuous increase of Europe's older population will prove to become a challenge for public health professionals not only for diagnosis and monitoring, but also for the treatment of glaucoma.

Resource use and costs for a glaucoma screening program in Austria: an 8-year review: a cost-consequence analysis based on the Salzburg-Moorfields Collaborative Glaucoma Study.

PURPOSE: The aim of this study is to report costs, detection rates, and resources needed for detection of primary open angle glaucoma and related diseases in a glaucoma screening program in Salzburg, Austria, over a period of 8 years. METHODS: The Salzburg-Moorfields Collaborative Glaucoma Study performed a complete ophthalmologic examination on a total of 4864 subjects within a study period of approximately 8 years (98 months). The total numbers reported are total number of subjects screened at the initial examination and follow-up examinations; total working hours and estimated working hours per visit for one ophthalmologist and two medical assistants; direct costs per visit; detection rates for subjects; and corresponding costs per true positive case diagnosed with definite primary open angle glaucoma (POAG), early POAG, POAG suspect, ocular hypertension (OHT), and glaucoma artefact. RESULTS: Within the screening period of 98 months, a total of 9427 examinations and second verification checks were performed: 5466 at the initial examination, 404 at the 1-year follow-up, 815 at the 2-year follow-up, 339 at the 3-year follow-up, 225 at the 4-year follow-up, 1059 at the 5-year follow-up, 996 at the 6-year follow-up, 118 at the 7-year follow-up, and 5 at the 8-year follow-up. The total amount of time spent for screening was 23,814 working hours. We estimate the costs per visit at EUR 123 for each initial examination, EUR 28 for each second confirmation check, and EUR 95 per follow-up examination. The following detection rates were observed: definite POAG: 1.7% (95% CI: 1.3-2.2%), early POAG: 2.9% (95% CI: 2.3-3.5%), POAG suspect: 8.5% (95% CI: 7.6-9.4%), OHT: 2.2% (95% CI: 1.7-2.7%), glaucoma artefact or other causes: 5.8% (95% CI: 5.1-6.6%), normal cases: 79% (95% CI: 78-80%). CONCLUSIONS: Direct costs per visit were considerably higher than those reported in the Netherlands or the United Kingdom. If a health care provider decides to perform a glaucoma screening within this setting, the costs for the detection of a new case are EUR 7250 for definite POAG, EUR 4250 for early POAG, EUR 1450 for POAG suspect, EUR 5600 for OHT, EUR 2100 for glaucoma artefact case, and EUR 156 for a normal case.

Ocular involvement in anti-epiligrin cicatricial pemphigoid.

PURPOSE: To report an anti-epiligrin cicatricial pemphigoid (AECP) patient with severe ocular involvement and to provide a practical approach to distinguishing AECP patients from those with other subepidermal blistering diseases. METHODS: Techniques included direct and indirect immunofluorescence microscopy, Western blot and immunoprecipitation studies, as well as interdisciplinary examinations of mucous membranes and skin. RESULTS: This study describes a patient with clinical features of cicatricial pemphigoid, circulating anti-basement membrane zone IgG antibodies, and subepidermal blisters. Histopathology and immunofluorescence analysis suggested the diagnosis of a cicatricial pemphigoid-like type of epidermolysis bullosa acquisita. However, Western blot and immunoprecipitation studies demonstrated that the patient's serum contained autoantibodies against laminin 5 alpha3 subunit, leading to the diagnosis of an AECP. CONCLUSION: Since patients with AECP have an increased relative risk for malignant tumors, it is important to distinguish this entity within the spectrum of cicatricial pemphigoid patients by additional studies such as Western blot or immunoprecipitation.

Measurement of stray light and glare: comparison of Nyktotest, Mesotest, stray light meter, and computer implemented stray light meter.

AIM: To evaluate the properties of devices for measuring stray light and glare: the Nyktotest, Mesotest, "conventional" stray light meter and a new, computer implemented version of the stray light meter. METHODS: 112 subjects, divided in three groups: (1) young subjects without any eye disease; (2) elderly subjects without any eye disease, and (3) subjects with (early) cataract in at least one eye. All subjects underwent a battery of glare and stray light tests, measurement of visual acuity, contrast sensitivity, refraction, and LOCS III cataract classification. Subjects answered a questionnaire on perceived disability during driving. RESULTS: Repeatability values were similar for all glare/stray light tests. Validity (correlation with LOCS III and questionnaire scores), discriminative ability (ability to discriminate between the three groups), and added value (to measurement of visual acuity and contrast sensitivity) were all superior for both stray light meters. Results of successive measurements are interrelated for the conventional but not the new stray light meter. This indicates a better resistance to fraud for the latter device. CONCLUSIONS: The new computer implemented stray light meter is the most promising device for future stray light measurements.

Implantable inlay devices for presbyopia: the evidence to date.

By 2020, it is estimated that 2.1 billion people will be presbyopic, and the demand for spectacle independence in this group is growing. This review article provides an overview of the three commercially available corneal inlays for the correction of presbyopia. Safety, efficacy, visual outcomes, and complications are analyzed for all three inlays according to published peer-reviewed data.

Monoglyceride lipase deficiency causes desensitization of intestinal cannabinoid receptor type 1 and increased colonic µ-opioid receptor sensitivity.

BACKGROUND AND PURPOSE: Monoglyceride lipase (MGL) degrades 2-arachidonoyl glycerol (2-AG), an endogenous agonist of cannabinoid receptors (CB1/2 ). Because the CB1 receptor is involved in the control of gut function, we investigated the effects of pharmacological inhibition and genetic deletion of MGL on intestinal motility. Furthermore, we determined whether defective 2-AG degradation affects µ-opioid receptor (µ receptor) signalling, a parallel pathway regulating gut motility. EXPERIMENTAL APPROACH: Gut motility was investigated by monitoring Evans Blue transit and colonic bead propulsion in response to MGL inhibition and CB1 receptor or µ receptor stimulation. Ileal contractility was investigated by electrical field stimulation. CB1 receptor expression in ileum and colon was assessed by immunohistochemical analyses. KEY RESULTS: Pharmacological inhibition of MGL slowed down whole gut transit in a CB1 receptor-dependent manner. Conversely, genetic deletion of MGL did not affect gut transit despite increased 2-AG levels. Notably, MGL deficiency caused complete insensitivity to CB1 receptor agonist-mediated inhibition of whole gut transit and ileal contractility suggesting local desensitization of CB1 receptors. Accordingly, immunohistochemical analyses of myenteric ganglia of MGL-deficient mice revealed that CB1 receptors were trapped in endocytic vesicles. Finally, MGL-deficient mice displayed accelerated colonic propulsion and were hypersensitive to µ receptor agonist-mediated inhibition of colonic motility. This phenotype was reproduced by chronic pharmacological inhibition of MGL. CONCLUSION AND IMPLICATIONS: Constantly elevated 2-AG levels induce severe desensitization of intestinal CB1 receptors and increased sensitivity to µ receptor-mediated inhibition of colonic motility. These changes should be considered when cannabinoid-based drugs are used in the therapy of gastrointestinal diseases.

Characteristics of an epidermal cell thymocyte-activating factor (ETAF) produced by human epidermal cells and a human squamous cell carcinoma cell line.

In this study we show that both cultured normal human epidermal cells (EC) and a human squamous cell carcinoma (SCC) cell line produce a thymocyte-activating factor (ETAF). EC-ETAF and SCC-ETAF both have a Mr of 15,000 and were eluted from chromatofocusing at the same isoelectric points of 7.2, 5.8, and 5.0. Both activities were maintained at alkaline pH and were destroyed at temperatures above 60 degrees C. In addition to stimulating thymocyte proliferation, human ETAF exhibited a variety of other pertinent biologic activities. Although EC-ETAF or SCC-ETAF by themselves exhibited no T-cell growth factor activity, both ETAF preparations enhanced Interleukin 2 production by cultured human peripheral blood lymphocytes when stimulated with polyclonal T-cells stimulants (Concanavalin A and phorbol myristate acetate). Human ETAF also was chemotactic for rabbit polymorphonuclear leukocytes and was directly mitogenic for cultured human dermal fibroblasts. Injection of human ETAF into C3H/HeJ mice, resulted in inducing serum amyloid A (SAA) production by murine hepatocytes. The thymocyte growth-enhancing activity, the fibroblast-stimulating activity, and the SAA-inducing capacity of ETAF all coeluted off AcA54 gel. These biologic as well as biochemical properties of human keratinocyte-derived ETAF are identical with those of human macrophage-derived Interleukin 1. The ability of keratinocytes to release an immunomodulating factor with such diverse consequences may play an important role in normal wound healing and in diseases involving epithelial tissues.

Macrophage-like properaties of human hyalocytes.

The cortical layer of the vitreous body of the eye contains a homogeneous population of hyalocytes. These cells were prepared from human autopsy eyes under sterile conditions by incubating the vitreous gel in tissue culture medium containing 300 micrograms/ml hyaluronidase. With the use of trypan blue staining, 60% to 90% of the cells were viable; they stained strongly for an intracellular nonspecific esterase with alpha-napthylacetate as a substrate. This staining could not be inhibited by sodium fluoride. The hyalocytes showed adherence to glass and plastic surfaces and phagocytosed latex spheres of 1.1 micrometer diameter. On their surface, receptors for IgG and complement components could be demonstrated with a rosette-forming technique using sensitized sheep erythrocytes. All these features strongly support the assumption that hyalocytes are mature cells of the mononuclear phagocyte system.

The effect of K-582, a new antifungal agent, on experimental Candida keratitis.

K-582, a new basic peptide antibiotic, was tested in rabbits with experimental Candida keratitis. It was shown that the K-582-treated group showed statistically highly significant therapeutic effects on days 2 and 3, as compared with the control group (day 2: P less than 0.001; day 3: P less than 0.001). The culture study showed that the average number of colonies was 1,573.1 in the controls and 463.3 in the treated group, and the difference was highly significant statistically (P less than 0.001). No ocular or systemic toxic effects were observed with this drug. K-582 is a promising new drug for the treatment of Candida keratitis.

Corneal epithelial cell--derived thymocyte-activating factor (CETAF).

Supernatants of a primary rabbit corneal epithelial cell culture and an established corneal cell line (SIRC) were assayed for their ability to enhance mitogen-induced C3H/HeJ mouse thymocyte proliferation. Significant levels of thymocyte-enhancing activity were detected in supernatants from both primary cultures and SIRC. Maximal levels of activity were found after 48 to 72 hr of culture in serum-free medium with 1 X 10(5) cells/ml. When monolayers of SIRC were disrupted. supernatants of these cultures consistently contained levels of activity higher than those of undisrupted control cultures. When supernatants from SIRC cultures (both serum-free and containing greater than 10% fetal calf serum) were subjected to gel filtration on AcA 54 and Sephacryl S-200, corneal epithelial cell-derived thymocyte-activating factor was eluted as two major peaks, between mol. wt 95,000 and 55,000 and mol. wt. 30,000 and 15,000. These results indicate that corneal epithelial cells, similar to keratinocytes, produce an Interleukin 1-like activity lacking species specificity, which enhances the proliferative capacity of thymocytes. Therefore corneal epithelial cells may interact with the immune system through the production of this cytokine.

Suppression of secondary herpes simplex uveitis by cyclosporine.

The authors studied the effect of an immunosuppressive agent, cyclosporine (CyA), on experimental secondary herpes simplex (HS) uveitis. Secondary HS uveitis was induced in a rabbit eye that had recovered from primary HS uveitis by challenging it with an intravitreal injection of herpes simplex virus (HSV) antigen. Daily intramuscular injections of CyA (25 mg/kg body weight) for 7 days prior to the intravitreal challenge with HSV antigen significantly suppressed the induction of secondary HS uveitis, but daily injections of CyA after the challenge with HSV antigen was ineffective. Intravitreal injections of CyA (5 mg) 7 days and 3 days prior to the HSV challenge were less effective, but the combined treatment with seven daily intramuscular CyA and two intravitreal CyA injections prior to the HSV challenge was most effective in the prevention of the uveitis. The daily intramuscular treatment with CyA resulted in a marked reduction of cell-mediated immunity while leaving the level of circulating HSV specific antibody high. No reactivation of latent HSV was detected in trigeminal and superior cervical ganglia of CyA-treated rabbits.

Retinal pigment epithelial cells in post mortem HLA typing of corneal donors.

Corneas used for transplantation are typically obtained from donors up to 48 hr post mortem. By this time, standard HLA typing usually is impossible because of the lack of viable lymphocytes in spleen and peripheral blood. To increase the number of HLA-typed corneas, we developed a method in which the retinal pigment epithelial (RPE) cells of the donor eye are isolated, cultured in the presence of 1000 IU/ml interferon-gamma (IFN-gamma), and, after 4 d, are typed for HLA Class I and Class II antigens in the standard NIH cytotoxicity assay. Sixty five donors were typed simultaneously using peripheral blood lymphocytes and RPE. One hundred and sixteen out of 120 HLA-A antigens, 125/127 HLA-B, 106/108 HLA-C, and 92/100 HLA-DR antigens were identical using the same technique. Donor age, sex, cause of death, time of enucleation post mortem, and time of RPE preparation post mortem, as well as duration of culture period prior to stimulation with IFN-gamma did not correlate with the results of HLA typing. These data show that RPE cells can substitute for lymphocytes in post mortem HLA typing. Consequently, every donor with corneas suitable for transplantation can be prepared for matched transplantation.

Penetration of norfloxacin into the aqueous humor of the human eye.

Forty six patients received a topical application of a 0.3% norfloxacin (Zoroxin; MSD, Austria) solution into the lower fornix at different time intervals and frequencies before undergoing planned extracapsular cataract extraction. Aqueous humor was sampled at the beginning of surgery and assayed for the level of the antibiotic with high performance liquid chromatography. The highest aqueous humor level observed 30 min after the administration of the last drop in four patients who received five drops of norfloxacin into the lower fornix was 660.25 +/- 378.2 ng/ml. These concentrations are above the minimum inhibitory concentration of norfloxacin for 90% (MIC90) of most of the gram-negative microorganisms, but below the MIC90 of most of the staphylococci (coagulase negative Staph. and Staphylococcus aureus range between 0.25-1 mg/ml).

Biologic properties of the thymocyte-activating factor (CETAF) produced by a rabbit corneal cell line (SIRC).

Rabbit corneal epithelial cell cultures produce a cytokine (CETAF) that greatly enhances the proliferation of C3H/HeJ mouse thymocytes. The rabbit corneal cell line SIRC was used to generate CETAF activity in the culture supernatant. CETAF was then partially purified by Sephacryl S-200 gel filtration, where peaks of activity eluted in a molecular weight range of 95,000-55,000 (CETAF I) and 30,000-15,000 (CETAF II). Similar to the epidermal cell-derived thymocyte-activating factor (ETAF), CETAF (I and II) stimulated the growth of a human dermal fibroblast line (CRL 1445) in a dose-dependent manner, but failed to enhance the proliferation of an Interleukin 2 (IL 2)-dependent T-cell line (CT 6). Although CETAF did not exhibit any IL 2 activity, it clearly enhanced the IL 2 production by C3H/HeJ mouse splenocytes stimulated with suboptimal doses of lectins. Crude SIRC supernatants as well as the partially purified CETAF preparations showed a marked inhibition of polymorphonuclear neutrophil migration at high concentrations, but were significantly chemotactic when diluted samples were tested. CETAF release by SIRC cells was increased by stimulation with mitomycin C, phorbolmyristate acetate, hydroxyurea, silica, lipopolysaccaride B, and when the cells were cultured under serum-free conditions. These observations suggest that corneal epithelial cells may not only interact with the immune system in a way similar to keratinocytes, but may also stimulate corneal stromal cell through the production of CETAF.

Expression of MHC class II antigens on rat bone marrow cells and macrophages, and their modulation during culture with murine GM-CSF or M-CSF.

Flow cytometric analysis employing MRC OX 6 and MRC OX17 monoclonal antibodies recognizing determinants on RT1.B or RT1.D molecules, equivalent to murine I-A and I-E, respectively, was used to detect rat MHC class II antigen (Ag) expression. Approximately 5% of freshly isolated rat bone marrow cells (BMC) expressed RT1.B and over 30% displayed RT1.D molecules. The RT1.D+ cells were W3/13+, OX 7+, OX 19- and OX 22-. After one week culture of BMC with murine recombinant granulocyte/macrophage colony-stimulating factor (GM-CSF), regardless of concentrations, 90 to 95% of the cells were scored as bone marrow-derived macrophages (BMDM phi), and over 30% expressed both RT1.B and RT1.D Ag. GM-CSF increases the percentage of BMDM phi bearing MHC class II Ag in a concentration-dependent manner. This effect seems to be specific because antibodies to interferon-gamma, tumor necrosis factor-alpha or interleukin-4 did not reduce the number of cells expressing RT1.B and RT1.D Ag. Furthermore, GM-CSF was able to trigger expression of class II molecules on rat peritoneal macrophages (M phi) and BMDM phi resulted from cultures of BMC with mouse M phi-CSF (M-CSF), and the RT1.B and RT1.D inducing effect of GM-CSF was opposed by M-CSF, and by anti-GM-CSF antibodies. The induction of MHC class II Ag synthesis by GM-CSF on rat BMDM phi was confirmed at the mRNA level by Northern blot analysis employing cDNA probes encoding the RT1.B alpha.