Primary interaction between I 131 labeled ragweed pollen and antibodies in the sera of humans and rabbits

Abstract

1. 1. Ragweed pollen extract was fractionated with 50 per cent saturated ammonium sulfate (SAS) and the supernatant labeled with I 131. 2. 2. When 0.02 γ N of this heterogenous mixture (I∗RW) was incubated with normal human or rabbit sera, approximately 10 per cent was nonspecifically precipitated with the globulins after the addition of 40 per cent SAS. 3. 3. After incubation with sera from humans or rabbits immunized with ragweed pollen extract as much as 40 to 60 per cent of the I∗RW was precipitated in 40 per cent SAS. 4. 4. Lesser degrees of increased precipitation of I∗RW were demonstrated with as little as 0.5 ml. of a 1:100 ragweed-injected human antiserum or 0.5 ml. of a 1:2000 ragweed-immunized rabbit antiserum. 5. 5. That the increased I∗RW precipitated by immune sera after the addition of 40 per cent SAS was due to binding by specific antibody rather than nonspecific co-precipitation was evidenced by: (a) rabbit antisera of high titer for bovine albumin, bovine globulin, human globulin, and Type 12 streptococcal M-protein precipitated no more I∗RW than did normal rabbit serum; (b) excess unlabeled ragweed pollen antigens completely inhibited the binding of I∗RW by human or rabbit anti-ragweed sera; and (c) apparently unrelated antigens did not inhibit the reaction. 6. 6. Determinations of the precipitation of I∗RW on different occasions by a pair of selected control sera demonstrated the reproducibility of the method and the stability of the labeled extract.