Immune response in the turtle (Chrysemys picta).

The immune response of painted turtles () to four purified protein antigens was evaluated by radioimmunoelectrophoresis. Specific antibody production was consistently detected and antigen binding was related to four immunoglobulin (Ig) precipitin lines (called Ig1, 2, 3, 4) in turtle serum. Antibody activity was detected first in the Ig1 or Ig2 and then later in the course of immunization in Ig3 and Ig4. Ig1 was about 19S in size, was not detectable after reduction and alkylation, and was the only Ig absent from turtle lymph. Ig3 and Ig4 were about 7S in size and Ig2 appeared slightly heavier by sucrose density gradient and Sephadex G-200 analysis. Haemagglutinins produced after primary inoculation were routinely sensitive to mild reduction and alkylation although antigen-binding capacity was still detectable. However, mercaptoethanol-resistant haemagglutinins were found in sera from turtles after booster injections of antigen. The electrophoretically slowest gamma globulin in turtle serum did not develop specific antigen-binding capacity, but did bind Fe and presumably represents a transferrin-like protein.