Abstract
Cholesterol as ordinarily prepared is now known to be contaminated with another sterol of an unsaturated and labile type of which ergosterol is the only known representative. Moreover, it is because of this contaminating sterol, ergosterol, that after irradiation with ultra-violet light, cholesterol acquires antirachitic properties. After removal of ergosterol, cholesterol is inert, following irradiation.
Professor Knudson of the Albany Medical College very kindly offered a supply of relatively pure cholesterol and ergosterol and suggested that a comparative study be made to determine whether the sensitizing action which cholesterol has upon the antigen used in the complement-fixation test for syphilis is also due to the presence of the contaminating sterol, ergosterol.
The antigen used was an alcoholic extract of dried, ether-extracted beef heart tissue. A comparison of the activity of the untreated antigen and of the antigen sensitized with the different samples of cholesterol and ergosterol used was made in a series of complement titrations carried out in the presence of antigen alone, serum alone and combinations of normal serum and antigen and syphilitic serum and antigen. With a few normal and syphilitic sera the relative differences in specific activity of the sensitized and unsensitized antigen were thus made apparent and the results further confirmed by comparative complement-fixation tests of the sera from 44 persons having syphilis and of 9 sera from apparently healthy individuals.
In these experiments, the sensitizing action of a sample of cholesterol which was purified by the dibromide method to remove the contaminating sterol, ergosterol, was found to be practically equal to that of the unpurified sample. Moreover, ergosterol alone in the amounts in which it might be present as a contaminant of cholesterol, namely, 0.0002% to 0.02%, had practically no sensitizing action. It appears, therefore, that the sensitizing action of cholesterol, as ordinarily prepared, on antigens in the complement-fixation test is not due to the contaminating sterol, ergosterol.
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