Staphylococcic toxoid is a stable product under suitable in vitro conditions. Dilution does not affect its stability.

Dilution of staphylococcic toxoid enhances its antigenicity by the intravenous route of administration. When given subcutaneously the diluted material does not appear to be a better antigen but, at least, it is as effective as unmodified toxoid in evoking antitoxic response in rabbits.

The antigenic in vivo response to toxoid roughly parallels the in vitro potency in terms of antitoxic binding units.

The addition of varying amounts of formalin to staphylococcic toxin, with subsequent incubation at 37°C., influences the rate of detoxication and loss of antitoxic binding power of the product. Between limits of 0.05 and 1 per cent formalin, the rate of detoxication was inversely proportional to the amount of formalin added, detoxication being complete within 24 hours in the case of those preparations containing 0.5 and 1 per cent formalin respectively. With lesser amounts of added formalin, detoxication was proportionately delayed. The more rapid the detoxication the smaller was the drop in potency in terms of antitoxic binding units and antigenic response in rabbits.

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