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¹²⁵I-labelled ovalbumin (OVA) antigen did not sensitize guinea-pigs and anaphylaxis did not develop after native OVA challenge. The radiolabelled antigen was fixed by lymphocytes with highly specific receptors for ¹²⁵I-OVA and this condition produced a continuous radiation damage leading to inactivation of the cells. As the proliferative response of lymphocytes did not occur, no antibody production was detected. This was demonstrated by passive haemagglutination techniques. However, the immune response to a simultaneously given non-radioactive antigen remained intact. It is supposed that radiation damage depended on specific activity of antigen destroying the antigen-specific lymphocyte clone selectively. The mechanism and the practical importance of the in vivo ‘antigen suicide’ is discussed.

Single stranded polyadenylic acid (Poly A) administered locally inhibited passive cutaneous anaphylaxis in mice. In experiments performed by equilibrium dialysis Poly A was able to bind histamine. The association constant of the reaction was determined, Ka = 1.3 +/- 0.2 x 10(5) I/M. One Poly A molecule can bind maximally two molecules of histamine dichloride. Poly A inhibited the antigen-induced release of histamine from the peritoneal rat mast cells when it was given together with sensitizing antibodies.

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