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Biomedical subjects

V Koistinen

Publications and source records attributed to V Koistinen.

28 records · Page 2Linked to original sources
PubMed1989

Common binding region of complement factors B, H and CR1 on C3b revealed by monoclonal anti-C3d.

Fab fragments of a murine C3d-specific monoclonal antibody, clone 4C2, strongly inhibited the binding of H, and up to about 80% that of B, to C3b on sheep erythrocytes, as shown by using radiolabelled purified proteins. The inhibition was also detected in the fluid phase. Conversion of C3 by preformed solid phase alternative pathway C3 convertase was not affected by 4C2. Also, it did not affect the decay rate of the convertase, but reduced the decay-accelerating effect of H on it. The results suggest that the binding sites of B and H on C3b are close to each other, and their competition for binding to C3b is focused around the C3d region. In addition, 4C2 partially blocked noncovalent binding of C3b to human erythrocytes, which suggests that CR1 also binds close to the H- and B-binding region in C3b.

Antibodies, Monoclonal↗
PubMed1983

Detection of hepatitis B surface antigen using time-resolved fluoroimmunoassay.

Conventional fluoroimmunoassay (FIA) methods based on various fluorescence principles have not achieved the sensitivity of radioimmunoassay (RIA) mainly because of problems of background fluorescence arising, for example, from the biological specimen. We now describe an immunoassay of hepatitis B surface antigen (HBsAg) based on time-resolved (TR) fluorescence using a lanthanide as label. The assay initiates the development of a new generation of immunoassays. The fluorescence intensity is measured after a selected delay time which almost completely eliminates background fluorescence, which has a fast decay time. The excitation is performed with a flashing light source. The molecules with a long fluorescent lifetime consist of chelates of rare earth metals (Eu, Tb, Sm, Dy). They absorb strongly the excitation radiation and transfer the energy to the chelated central atom which in turn produces an emission spectrum characteristic of the lanthanide used. A long Stokes' shift (greater than 270 nm) helps to reduce the background in the emission region of the chelate and thus optimizes measurement of the relevant fluorescence. The present TR-FIA uses 2-naphthoyltrifluoroacetone as chelating agent because it creates an intense fluorescence with the rare earth metals. Synergistic agents such as trioctylphosphineoxid further enhance the fluorescence of the chelate. Depending on the instrumentation used for measuring time-resolved fluorescence and the conditions used for chelate formation, lanthanides can be detected at 10(-12)-10(-14)M concentrations.

Fluorescent Antibody Technique↗
PubMed1979

Anti-HBe and subtypes of HBsAg among asymptomatic HBsAg carriers.

Finnish HBsAg positive blood donors were analyzed for the HBsAg subtype distribution and the presence of e antigen (HBeAg) and antibody to e (anti-HBe). 88% (159 of 180) of the donors had subtype and ad and 12% (21 of 180) had ay. HBeAg was found in 1% (2 of 180) and anti-HBe in 74% (133 of 180) of the donors. Anti-HBe was significantly (p less than 0.0001) more common among donors with subtype ad than with ay: 80 and 29% respectively. The mean age of donors with both subtype ad and anti-HBe was significantly (p less than 0.001) lower than that of the other donor categories.

Adult↗
PubMed1978

Use of ELISA for measuring immunoconglutinins.

An enzyme-linked immunosorbent assay (ELISA) for detection of immunoconglutinins (IKs) has been developed. IKs are allowed to bind to solid-phase C3 and are then assayed using alkaline phosphatase coupled to anti-IgG or anti-IgM. IK activity was detected in some patients' sera up to 50,000-fold dilution. Significant correlation (r = 0.65) was obtained between the levels of IgM-IKs measured by ELISA and by conventional hemagglutination assay, IgG-IKs and hemagglutination titers did not correlate (r = -0.15).

Alkaline Phosphatase↗
PubMed1978

A coated-tube radioimmunoassay (FRC-RIA) for hepatitis B surface antigen.

A sandwich-type solid phase radioimmunoassay, FRC-RIA (Finnish Red Cross-RIA) for hepatitis B surface antigen (HBsAg) is described. Polystyrene test tubes coated with sheep anti-HBs gamma-globulin serve as the solid phase. The technique is specific and has a sensitivity of about 1 ng/ml for the subtypes ad and ay of HBsAg when corresponding subtype-specific antibodies are used as reagents. The total incubation time can be shortened from over 20 h to 3 h, with almost equal sensitivity, when the incubation temperature is raised from room temperature to 45 degrees C. The test is economical in reagents and is applicable to routine use.

Antibodies, Viral↗
PubMed1977

Enzyme-immunoassay in the detection of hepatitis B surface antigen.

A new enzyme-immunoassay (EIA, Hepanostika Microelisa System) for the detection of hepatitis B surface antigen was evaluated against other methods, namely complement fixation, Hepanosticon, AusRIA II and Finnish Red Cross Radioimmunoassay (FRC-RIA). EIA detected the greatest number of positive samples in a serum panel consisting of 142 sera from clinical hepatitis patients. FRC-RIA was the most sensitive method for subtype ad, while EIA detected the ay specimen at the highest dilution. None of the test systems gave the 'optimal' result in the screening test, and it is proposed that a separate procedure for each antigen subtype should be carried out to detect the greatest number of positive samples.

Complement Fixation Tests↗