Quantitative determination of titers of anti-zona serum

The titers of rabbit antiserum against isolated mouse zonae pellucidae were examined by several methods in connection with inhibitory effect on fertilization. The titers determined by zona precipitate, zona dissolution, indirect immunofluorescence and in vitro fertilization tests were 2(4), 2(1) to 2(4), 2(7) and 2(4), respectively. Cytotoxic effect could not be detected from zona antibody. The indirect immunofluorescence was most sensitive for detection of zona antibody but did not represent the extent of inhibitory effect on fertilization. The titer obtained by zona precipitate test was most close to the titer obtained by inhibitory effect on in vitro fertilization. The present study also demonstrated that at least 0.0375 ml of antiserum per female mouse, equivalent to 0.15-0.25% of body weight, was necessary for inhibition of fertilization in vivo by passive immunization with anti-zona serum.