Communications

Abstract

Summary When EAC′1 (erythrocytes sensitized by antibody and the first component of complement) are prepared with an amount of IgG antibody (Ab) just sufficient to produce about 100 C′1-fixing sites/cell, the C′1 can be quantitatively transferred from these cells in a short time at 30°C at ionic strength (µ) = 0.063. If 50 times as much IgG Ab is used, but C′1 is limited to produce about 100 or fewer SAC′1/cell, then almost no C′1 transfer occurs at 30°C, µ = 0.063, but much of the C′1 will transfer at µ = 0.14. It is suggested that C′1 bound to IgG dimers transfers readily at µ = 0.063, while C′1 bound to IgG trimers transfers readily only at µ = 0.14 or higher, and C′1 bound to IgG tetramers may fail to transfer altogether. With IgM Ab, a slight similar effect was noted, to the extent that for equivalent amounts of C′1 transfer it was necessary to increase the ionic strength as larger amounts of IgM were used to sensitize erythrocytes.