Immunofluorescence studies with 4-acetamido-4'-isothiocyanato stilbene-2,2'-disulphonic acid (SITS).

The application of the fluorochrome 4-acetamido-4'-isothiocyanato stilbene-2,2'-disulphonic acid (SITS) in immunofluorescence was studied. The optimal excitation wave length is 350 nm, and optimal fluorescence is obtained at 420 nm. After purification of the commercial compound, conjugation is performed in a strong buffer at pH 9.0-9.5. SITS conjugates were very satisfactory for immunofluorescence studies of the cytoplasmic antigens of cell preparations, but their blue emission was difficult to distinguish from autofluorescence in sections of human tissues. Good results with immunofluorescence on membrane bound antigens were obtained by using an ultra-violet laser beam as light source. SITS can be used simultaneously with FITC and TRITC conjugates thus making it possible to show three antigens in one preparation.

[Prenatal study of trisomy 21: triple test more efficient than age criterion]. / Prenataal onderzoek op trisomie 21: tripletest efficiënter dan leeftijdscriterium.

OBJECTIVE: To compare the results of selection of gravidae for trisomy 21 testing on the basis of age or of the triple test. DESIGN: Theoretical evaluation. METHOD: Demographic statistical data for the years 1980, 1985, 1990 and 1994 and the age-specific risk were used to calculate the expected number of children to be born with trisomy 21. Also calculated were the size of the risk groups, the number of children with trisomy 21 to be detected early, the iatrogenic loss of pregnancy and the number of invasive tests to be performed in order to detect one child with trisomy 21 with either selection method. RESULTS: Shifting of pregnancy to women with a mean older age results in a increase of the risk group as determined by age. It will also result in an increase of the number of iatrogenic losses of pregnancy. Selection of the risk group by the triple test will not result in these increases. The risk group, as determined by the triple test, includes about 60 per cent of the women pregnant of a child with trisomy 21; that determined by age 23 to 30 per cent. The number of invasive tests to be performed for the detection of one child with trisomy 21 is significantly smaller in case of selection by the triple test. CONCLUSION: By application of the triple test less pregnant women have to be further examined and more cases of trisomy 21 are detected, than by application of the age criterium.

Light chain type ratio of IgA-producing cells in human jejunal biopsies.

As part of an investigation on a possible relationship between the serum IgA and the immunoglobulins synthesized by the plasma cells in the intestinal mucosa, immunoglobulin-producing cells in human jejunal biopsies were characterized by class and type of intracellular immunoglobulins. In biopsy Specimens from 22 patients, with various diagnoses except multiple myeloma, the average percentage of IgA-producing cells was 83 percent, that of IgG-producing cells 5 percent and that of IgM-producing cells 12 percent, with a wide range for individual patients. For the IgA-producing cells the kappa/lambda ratio was determined and the average ratio was found to be 63 : 37, within a very limited range for individual patients. There was no correlation between the relative number of IgA-producing cells in the biopsy specimens and the IgA concentration in the serum. Additionally biopsy specimens from 3 patients with a monoclonal immunoglobulin-A component in their serum were studied. In one of those there was a remarkable shift in the kappa/lambda ratio, indicating that the light chain distribution of the intestinal IgA plasma cells was affected by the lympho-proliferative process.

Kappa-chain deficiency. An immunoglobulin disorder.

Since kappa-chain deficiency is an unusual condition, we studied the clinical and laboratory findings in a patient with this deficiency. The patient had cystic fibrosis with concurrent malabsorption, diabetes mellitus and IgA deficiency. The serum levels of IgM and IgG were 0.85 and 7.22 mg per milliliter, respectively. Kappa type IgM and IgG was not present in serum and external secretions; gamma, mu and lambda chains were probably polyclonal in character. Antibodies against kappa chains were not detected in either the patient or the mother. Plasma cells containing kappa-type immunoglobulins were absent in jejunum samples and bone marrow; kappa-chainbearing B lymphocytes could not be detected in blood and bone marrow. The serum of one of the patient's sisters contained trace amounts of kappa-type immunoglobulins. The patient displays a complete absence of kappa-type immunoglobulins, probably owing to a genetic defect.