Labeling of antibodies with radioactive isotopes in plant virus serology

Antibodies isolated from antiserum against plant viruses were labeled with the isotope³⁵S as follows: the mixture of antibodies with radioactive cysteine hydrochloride was allowed to stand for half an hour, run on a Sephadex G-25 column and individual fractions were collected. Sephadex G-50 bed was equilibrated and washed with saline (0,85 % NaCl) phosphate buffer (0,01 m) pH 7,2. Fractions showing the highest radioactivity and at the same time the most evident serological reaction were combined and used as³⁵S labeled antibodies. The labeled antibodies were used for rubbing leaves; the leaves were afterwards incubated, washed, killed, dried and then subjected to autoradiography. The method of indirect serological reaction also proved to be very good. Using this method, pig gamma globulin against rabbit gamma globulin was labeled with³⁵ S; this labeled gamma globulin was then used to detect serological reaction on leaves between the virus and homologous rabbit antiserum and/or antibodies. The results of those reactions were also determined by autoradiography. Exact procedure for labeling antibodies, carrying out serological reactions and autoradiography is desribed.