Studies with Marked Antisera 2. Variation in the Specific Adsorption by Red Cells from Different Rabbits of One 131I-marked rabbit ISO-Antiserum

Abstract

1. An apparently pure rabbit iso-antibody marked with ¹³¹I has been shown to adsorb specifically to a greater extent on some rabbit cells than on others. This accords with previous evidence that the same iso-antibody exhibits a higher titre with the cells which are shown here to absorb more marked antibody than with those which adsorb less.2. Saturation of two of these red cell types by repeated application of fresh quantities of the ¹³¹I iso-antibody until no more is specifically adsorbed, suggests that the number of functional antigenic sites is six or seven times greater on the one than on the other cell.3. There is no apparent difference in the amount of ¹³¹I iso-antibody adsorbed by any one type of rabbit cell in comparative titrations using 3·3 % MgSO₄.7H₂O medium instead of normal saline.