On the mechanism by which antigen is removed from the circulation

Abstract

In studying the rate of disappearance of horse serum and the curves for circulating precipitin in a group of serum-treated patients it was noted that individuals who have severe serum disease are good precipitin formers and that at the time the precipitin in the circulation reaches the crest of its curve or soon thereafter the precipitinogen rapidly disappears from the blood stream. On the other hand in those individuals who after a first administration of foreign serum, show very mild or no symptoms of serum disease little or no precipitin is demonstrable in the patient's serum and the precipitinogen persists in the circulation for a long period. Intermediate types were also encountered. From these results it seemed at least plausible to assume that an important factor in determining the rate of disappearance of the foreign serum from the circulation was an intravascular union of antibody and antigen. That such an assumption is erroneous seems probable from the following experiments:

In one series of experiments 12 previously immunized rabbits were injected intravenously with amounts of horse serum (3.00 c.c. or 6.00 c.c.) comparable to the amounts used therapeutically in the group of patients studied. The animals were then bled every second or every third day and the precipitin and precipitinogen in the serum titrated. Six of the animals had a high titer (1:20,000 or higher) of precipitin in the circulation at the time of reinjection, 2 had a moderately high titer, 1 had only traces of precipitin, and 3 had no circulating precipitin. Two of the 3 rabbits with no circulating precipitin had been immunized 10 months previously and at that time had developed a high titer of precipitin which had entirely disappeared before the reinjection.