Studies on the effect of variation of concentration and origin of lecithin (natural and synthetic) in cardiolipin complement-fixation antigen.

The significance of the relationship between the three components of cardiolipin complementfixation antigen, viz. cardiolipin, natural lecithin, and cholesterol, was first studied by Maltaner and Maltaner (1945) in experiments with syphilitic pooled rabbit or human sera. Suitable sensitivity with regard to the routine sero-diagnosis of syphilis was obtained with the antigen formula: Cardiolipin (C) 1, lecithin (L) 5, and cholesterol (Ch) 17. A C/L ratio of I/1 5 and a Ch/L ratio of 5 or 6/1 appeared to form the upper limits of sensitivity. These results were confirmed by Lundback (1952). Other investigators (Harris and Portnoy, 1944; Kent, Boyd, and Sanders, 1948; Kolmer and Lynch, 1948) arrived at other suitable antigen formulae, and now at least six different formulae are in use (Chron. Wld Hith Org., 1955). Allen and Mason (1952) tested a larger series of human sera against four antigens with varying C/L and C/Ch ratios, and found the greatest sensitivity with antigen prepared with a C/L ratio of 1/1 7 and a C/Ch ratio of 1/10; however, the high sensitivity was obtained at the price of lower specificity. Price (1953 a, b, c), using a Ch/L ratio of 10/1, considered a C/L ratio of 1/1 to be most suitable for the Whitechapel complement-fixation technique. Later experiments showed that cardiolipin antigen of the above-mentioned composition "showed a greater liability to non-treponemal reactions" than the crude Price antigen formerly used (Price, 1954). In a previous investigation (Reyn, Bentzon, and Hartmann, 1956), in which the same five freeze-dried syphilitic sera were repeatedly tested in complementfixation experiments, the individual sera were found to respond somewhat differently to variation of the lecithin concentration, keeping the Cand Chconcentrations constant. The greatest sensitivity was