1965 Volume 20 Issue 4 Pages 183-194
Even if serodiagnosis of syphilis with FTA test, using fluorescent antibody to human γ-globulin has the advantages of being convenient, specific and highly sensitive, still it remains the problem of so-called biological false positive reaction in a debate. In order to investigate in detail the specificity of this test we tried first to study the distribution of antibodies, especially antibodies of 7S γ type in syphilitic sera in each stage.
Two kinds of the antiserum were used as anti-human γ-globulin. In order to get purified 7S γ-globulin 800mg of the same globulin was separated by chromatography on DEAE-cellulose as follows: 200ml of normal human serum was salted out with 33% saturated (NH4)2SO4 three times, whereafter it was transfered to a column (4.0×25.0cm) of DEAE-cellulose equilibrated with 0.01M phosphate buffer, pH7.5, containing 0.015M NaCl and eluted with the same buffer. Elution with this buffer gave a pure γ2-globulin peak as shown by cellulose acetate electrophoresis, Ouchterlony agar diffusion method and immunoelectrophoresis using LKB's immunophor. Then, anti-7S γ-globulin was prepared in rabbits following a course of immunization which included intramuscular injections of alum precipitated antigen (purified 7S γ-globulin preparation) and intravenous injections of 1% aqueous solution of the antigen and then γ-globulin fraction of thus raised antiserum was conjugated with fluorescein isothiocyanate (FITC). Its F/P ratio was estimated as 1.32×10-3. Immunoelectrophoresis with normal human serum showed a strong 7S γ line only.
We used FTA tests with this FITC-labeled anti-7S γ-globulin and with FITC-labeled anti-γ-globulin, in which the latter γ-globulin was prepared by routine ammonium sulfate precipitation and thus it contained both globulins of 7S γ and 19S γ types. Comparative studies were undertaken to investigate the transition of antibodies of 7S γ and 19S γ types in the syphilitic sera by both methods.
From our results it was found that 7S γ class antibodies appeared always in the sera of primary stage (2 cases), secondary stage (5 cases), tertiary stage (6 cases) and congenital syphilis (4 cases), but in contrast to this 19S γ class antibody was found only in the sera of primary syphilis. These findings seem likely to show the evidence that in the very early stages of syphilis macroglobulin (γ1M-globulin) antibodies appeared, but later predominantly 7S γ-globulin (γ2-globulin) antibodies.
One hundred thirty seven sera which were sent to our laboratory for FTA test, were tested also by RPCF, W.R. and VDRL tests, comparing with the results of this test. It was found that discrepancies of 20%, were encountered between FTA test and several other tests for syphilis (RPCF, W.R. and VDRL tests).
The present results show that FTA test is found to be most specific compared with the other three tests for syphilis, and also show the most promising results also in the cases of biological false positive reaction.
