The Harris Slide Test: A Microflocculation Test for Syphilis with Cardiolipin Antigen.

The antigens in common use for the serological diagnosis of syphilis, such as the complement fixation tests and the various flocculation tests, are alcoholic extracts of ox heart usually sensitized with cholesterol. If, however, cholesterol is added to the crude alcoholic extract, false positive reactions are not uncommon. On this account it has become customary to purify the alcoholic extracts of ox heart by first undertaking an extraction with ether, acetone, or ethylene perchloride to remove adventitious substances. But even these purified antigens, which contain the potent phosphatides, are not completely rid of non-specific substances. Of late years the active lipoid antigen constituents have been subjected to searching studies. It was not, however, until 1941, when Mary C. Pangborn succeeded in isolating a hitherto unrecognized serologically active phospholipid, cardiolipin, from ox heart, that an antigen consisting essentially of chemically pure substances was produced. Used alone as an antigen, cardiolipin is. anti-complementary. Mixtures of cardiolipin and purified lecithin have, however, been found highly antigenic, and when cholesterol is added to such mixtures sensitization is attained. Cardiolipin-lecithin-cholesterol antigens have been used in the complement fixation tests for syphilis by Harris and Portnoy (1944) and by Maltaner and Maltaner (1945), and also for various precipitation methods by Brown (1944, 1945), by Rein and Bossak (1946), and by Kline (1946). The cardiolipin-lecithincholesterol ratio has varied in the different techniques employed.