Fowl antibody: III. Its haemolytic activity with complements of various species and some properties of fowl complement.

Red cells sensitized with naturally occurring or immune' fowl antibody were lysed by fresh fowl serum. This fowl complement could not be replaced by that of human, rabbit or guinea pig. Both naturally occurring and immune' antibodies to red cells in the mammalian species tested did not lyse with fowl complement. Lysis by fresh fowl serum of sheep red cells sensitized with mammalian antibody is due to the presence of naturally occurring antibody to these cells in the fowl serum; the enhancement of this lysis by the mammalian antibody will be described more fully in the next paper. Naturally occurring antibody to sheep red cells present in turkey serum and `immune' antibody to fowl red cells were not lytic with fresh turkey serum, with fowl complement, with guinea-pig complement or with any combination of these. Some properties of fowl complement are given.