The most avidly complement fixing antibody is -

IgG is the main serum immunoglobulin consisting of 80% of the total. equally distributed between intravascular and extravascular compaments. IgG paicipates in most immunological reactions such as complement fixation, precipitation a, d neutralization toxins and virus. REF:Anathanarayan & paniker's 9th edition, pg no:97 <\p>