Complement fixation inhibiting and complement-fixing antibodies were demonstrated in sera from cats during the acute and convalescent stages, respectively, of feline picornavirus infections. Complement-fixing antibody activity was present in 19S and 7S globulins, whereas complement fixation inhibiting antibody activity was confined to the 7S globulins. Sera with complement-fixing antibody and s...

Complement-fixation inhibition test was adapted to the microtiter system. When cat and monkey non-complement-fixing antibody were used, the microtest was shown to be as sensitive as the conventional tube complement-fixation inhibition test.

In view of the drawbacks in the use of the Kahn test for large-scale screening of blood donors, mainly those of human error through work overload and fatiguability, an attempt was made to adapt an existing automated complement-fixation technique for this purpose. This paper reports the successful results of that adaptation.

The alkaline phosphatases of 29 strains of bacteria assigned by various authors to the genera Aerobacter, Klebsiella and Enterobacter were compared by the micro-complement fixation technique. On the basis of phosphatase resemblance, we recommend that all strains hitherto assigned to Aerobacter aerogenes and Enterobacter aerogenes be assigned to the genus Klebsiella.

The knowledge that exists of the role of complement in immune reactions has been gained from investigations limited almost entirely to studies in vitro. Very little is known of the role of complement in immune reactions in vivo. I t has not been demonstrated that complement fixation occurs in animal tissues in vivo in some way analogous to the fixation of complement to antigen-antibody aggregat...