Complement fixing antibody in animals injected with heat killed tubercle bacilli in oil appears earlier in the lesion at the site of injection than in the blood serum.
Complement fixing antibody in an extract prepared by suspending one part by weight of tissue from the local site in five parts of saline is in general in higher concentration than in the blood, for a period of approximately 3 weeks following injection. After this time the serum may show the higher titre.
The titre of antibody at the site of injection tends to increase with the quantity of heat killed bacilli injected into the skin, up to a definable maximum.
No evidence was found to support the opinion that local accumulation of antibody was caused by fixation of antibody contained in the serum and produced elsewhere in the body, for extracts of lesions produced by the injection of paraffin oil, old tuberculin, and cod liver oil showed no demonstrable antibody, or at most a very low titre, even when the serum titre was high. After reinjection of heat killed tubercle bacilli in oil into rabbits with antibody in the serum, antibody did not appear in the local lesion any earlier than in normal animals similarly injected.
These observations give evidence that antibody is formed in the skin at the site of injection of tubercle bacilli.