Facile generation of monoclonal antibodies suitable for conjugation

Monoclonal antibodies (mAb) are unique tools in therapeutics and immunodiagnostics applications but many of these applications rely on conjugated mAbs. Whether conjugating drugs or tracers, the conjugation process, frequently taking advantage of primary amines on lysine residues, may affect the binding activity of the antibodies. Furthermore, due to the sticky nature of many mAbs, unfavorable interactions may become eminent, with the result of high background signals. The workload associated with producing mAbs, able to withstand conjugation, preserving stability and affinity and avoiding off-target interactions, is comprehensive and related with only incidental success. We designed a method, where uncloned hybridomas were pre-selected for secretion of mAbs with the above characteristics. Using human collectin K1 (CL-K1, alias CL-11, Colec11) as a model antigen, mAbs present in culture supernatant from uncloned hybridomas were immobilized on Protein A beads, followed by solid phase biotinylation and subsequent elution. ELISA was employed to compare the binding activity of conjugated vs. unconjugated mAbs, and furthermore for their application in combination with other antibodies. From a group of 96 uncloned hybridomas we accomplished in obtaining five suitable mAbs, among which, two mAbs were superior. The successful conjugation of the selected mAbs with fluorophores and subsequent applications in microscopy and flow cytometry were further demonstrated. In conclusion, pre-selection of uncloned hybridomas, by testing of their mAbs' ability to withstand conjugation with tracers or drugs, is a successful strategy to avoid a huge workload of cloning numerous hybridomas, in order to obtain conjugatable mAbs.

Tear fluid analysis in patients with primary Sjögren's syndrome using lectin probes. A comparative study of patients with primary Sjögren's syndrome, patients with other immune inflammatory connective tissue diseases and controls

PURPOSE

To study and compare the glycoprotein composition of tear fluid from patients with primary Sjögren's syndrome, patients with other connective tissue diseases and control individuals.

METHODS

SDS polyacrylamide gel electrophoresis followed by Coomassie staining or Western blotting and overlaying with ten different lectins.

RESULTS

The frequency of many glycoprotein bands discovered was significantly decreased in primary Sjögren's syndrome compared with controls and patients with other connective tissue diseases. The reduction was most pronounced in the 14-68 kDa molecular weight range.

CONCLUSIONS

A decrease in the production rate and/or a change in the glycosylation pattern of the tear glycoproteins was found in patients with primary Sjögren's syndrome. The changes discovered, however, were not specific enough to be useful as a diagnostic test.

Snake-like chromatin in conjunctival cells of a population aged 30-60 years from Copenhagen City

PURPOSE

To investigate the frequency of snake-like chromatin in the conjunctival epithelial cells (SLC) of a population from Copenhagen City.

METHODS

A questionnaire was mailed to 504 persons aged 30-60 years. Persons with symptoms of ocular/oral dryness and a control group without symptoms were examined by the conjunctival imprint technique.

RESULTS

According to this material the frequency of SLC in persons 30-60 years living in Copenhagen may be estimated to 47%, which is considerably higher than earlier reported. In most cases SLC was, however, occupying less than 1% of the total cell area. No significant association was found to abnormal results of the Schirmer test, tear film break up time, rose bengal score or tear film lipid layer thickness. The frequency of SLC in persons with KCS was 53%, however, only few cases of KCS were found in the material.

CONCLUSION

Results indicate that SLC is a quite frequent and unspecific finding, probably reflecting chronic irritation of the ocular surface.

The ratio of albumin to lactoferrin in tear fluid as a diagnostic tool in primary Sjögren's syndrome

PURPOSE

To compare the protein composition of tear fluid obtained from patients with primary Sjögren's syndrome, patients with other connective tissue diseases and control individuals.

METHODS

SDS polyacrylamide gel electrophoresis followed by staining with Coomassie blue and Western blotting.

RESULTS

Comparison revealed the presence of a characteristic difference in the ratio of intensity between the albumin and lactoferrin bands. An albumin:lactoferrin ratio above 2:1 was significantly more common in patients with primary Sjögren's syndrome than in patients with other connective tissue diseases or the controls.

CONCLUSION

An albumin:lactoferrin ratio above 2:1 may therefore prove of use when diagnosing 1(0)SS. Used as a test, its sensitivity was 67% and its specificity 100%.

Keratoconjunctivitis sicca and primary Sjögren's syndrome in a Danish population aged 30-60 years

PURPOSE

To investigate the presence of keratoconjunctivitis sicca and primary Sjögren's syndrome a sample of 504 persons aged 30-60 years from Copenhagen was studied.

METHODS

The presence of keratoconjunctivitis sicca and primary Sjögren's syndrome was estimated according to both the Copenhagen set of criteria and the preliminary European criteria.

RESULTS

Symptoms of dry eye and oral dryness were very common and with no significant correlation to age or sex. Keratoconjuncitivis sicca was most frequent in persons aged 50-59 years and was equally common in men and women. Primary Sjögren's syndrome could only be diagnosed in one person according to the Copenhagen criteria (cut-off the Schirmer-1 test < or = 5 mm/5 min), and in three persons according to the preliminary European criteria.

CONCLUSION

The frequency of keratoconjunctivitis sicca in persons aged 30-60 years in Copenhagen may be estimated to be 11% according to the Copenhagen criteria and 8% according to the preliminary European criteria. The frequency of primary Sjögren's syndrome in persons aged 30-60 years in Copenhagen may be estimated to be between 0.2% and 0.8% according to the Copenhagen criteria and between 0.6% and 2.1% according to the preliminary European criteria.

Test and symptoms in keratoconjunctivitis sicca and their correlation

Results of dry eye tests and ocular symptoms were compared and correlated in patients with primary Sjögren's syndrome (1 degree SS), in patients with connective tissue disease differing from 1 degree SS, and in normal controls. Patients with 1 degree SS had many and pronounced ocular complaints, however, non-diagnostic for the disease. Break-up time and Schirmer-1 test results below 10 mm/5 min both had high sensitivity but low specificity, whereas the reverse was true for Rose-Bengal score and Schirmer-1 test below 5 mm/5 min. Presence of snake-like chromatin in conjunctival imprints and the lactotest on tear fluid did not qualify as alternative tests since they had very low specificity and were less sensitive than the Schirmer-1 test and break-up time. Cornea sensitivity was not found to be an appropriate test at all. In 21% of eyes the presence of keratoconjunctivitis sicca changed from one consultation to the next in patients with 1 degree SS. Examination for keratoconjunctivitis sicca should therefore be repeated in test negative cases where symptoms indicate 1 degree SS.

Snake-like chromatin in conjunctival cells of normal elderly persons and of patients with primary Sjögren's syndrome and other connective tissue diseases

The aim of this study was to investigate the prevalence of snake-like chromatin in the nuclei of conjunctival cells of normal elderly persons, and to compare with findings in patients with connective tissue diseases other than primary Sjögren's syndrome and in age-matched patients with primary Sjögren's syndrome. Thirty-nine per cent of the eyes of normal controls contained snake-like chromatin. Snake-like chromatin has almost never been found in young normals, and the results of this study therefore raise the question of whether age may be a contributing factor. Snake-like chromatin was as frequent in patients with other connective tissue diseases as in patients with primary Sjögren's syndrome, and no correlation to the presence of keratoconjunctivitis sicca was found in this group. The presence of snake-like chromatin was significantly correlated to increased cell size (N/C ratio) and low goblet cell density. A marked correlation between snake-like chromatin and low values of break-up time was found in normals, whereas no correlation was found to the other standard tests for dry eye.

[Risk of cataract surgery in patients with myopia. A prospective Danish multicenter study with special reference to a complication]

A prospective Danish multicentre study was conducted to evaluate the incidence of retinal detachment after cataract extraction in myopic eyes (axial length, > or = 25.5 mm). Two hundred and forty-seven cataract extractions in myopic eyes were reported during a period of 13 months. Two hundred and forty-one eyes underwent extracapsular and six eyes intracapsular cataract extraction. The mean follow-up time for 158 eyes was seven months (ranging from 1-30 months). In five cases a retinal detachment was observed, one case was probably present preoperatively, this person had undergone intracapsular cataract extraction. The incidence of retinal detachment was thus 1.62-2.02% in the total material and 1.66% in eyes operated with extracapsular cataract extraction.

Collection and concentration of tear proteins studied by SDS gel electrophoresis. Presentation of a new method with special reference to dry eye patients

An obvious obstacle in the analysis of tear film samples from patients with dry eyes is the drastically reduced tear volume. To overcome this problem we have developed a method by which the surface of the eye is flushed with saline, diluting the sparse tear fluid, followed by a concentration of the wash fluid. We compared undiluted tears, diluted tears, tear fluid collected by flushing, reconcentrated diluted tears and reconcentrated flush fluid. Gel electrophoresis of the tear samples obtained showed a representative collection of tear proteins, with bands ranging in molecular weight from about 10 kDa to about 90 kDa. The method may therefore provide a useful alternative to the analysis of undiluted tear fluid in such patients. After storage at -80 degrees C for 1 month, electrophoresis often showed some weakening of band intensities. However, no specific loss of bands was found, and by ultracentrifugation a band profile similar to that of fresh, undiluted tears was obtained. For most purposes, therefore, samples may be kept by this means for later analysis.

Preliminary criteria for the classification of Sjögren's syndrome. Results of a prospective concerted action supported by the European Community

OBJECTIVE

Different sets of diagnostic criteria have been proposed for Sjögren's syndrome (SS), but none have been validated with a large series of patients or in a multicenter study. We conducted the present study involving 26 centers from 12 countries (11 in Europe, plus Israel), with the goals of reaching a consensus on the diagnostic procedures for SS and defining classification criteria to be used in epidemiologic surveys and adopted by the scientific community.

METHODS

The study protocol was subdivided into two parts. For part I, questionnaires regarding both ocular and oral involvement were developed; they included 13 questions and 7 questions, respectively. For part II a limited set of diagnostic tests was selected, and the exact procedure to be followed in performing these tests was defined. Part I of the study included 240 patients with primary SS and 240 age- and sex-matched controls. Two hundred forty-six patients with primary SS, 201 with secondary SS, 113 with connective tissue diseases but without associated SS, and 133 control patients were studied in part II.

RESULTS

The study resulted in (a) the validation of a simple 6-item questionnaire for determination of dry eyes and dry mouth, which showed good discriminant power between patients and controls, to be used in the initial screening for sicca syndrome; and (b) the definition of a new set of criteria for the classification of SS. The sensitivity and specificity of the criteria in correctly identifying patients with either the primary or the secondary variant of SS were also determined.

CONCLUSION

Using the findings of this prospective multicenter European study, general agreement can be reached on the diagnostic procedures to be used for patients with SS. Final validation of the preliminary classification criteria for SS is underway.