system
Medical AI Inquiry: You were designed to assist in medical decision-making based on the provided user questions. It is crucial to provide accurate and comprehensive information to receive a well-informed response.
user
The most avidly complement fixing antibody is -
assistant
The correct answer 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>