Rosette-forming cells during immune response to Toxoplasma gondii in mice.

The rosette-forming cell (RFC) response of mice immunized with varying doses of Toxoplasma gondii was studied by immunocytoadherence (ICA). The specificity of ICA in the present system was tested by passive sensitization with hyperimmune serum in vivo and in vitro. A slight increase in RFC was observed with the latter. Prior treatment of spleen cells from immunized animals with rabbit anti-mouse immunoglobulin resulted in total inhibition of ICA. During the primary and the secondary response after 10 days, the number of RFC rose rapidly to reach the peak on the 3rd day. With secondary immunization 30 days later, the peak shifted to the 2nd day. Mice infected with a lower dose of Toxoplasma had a greater number of RFC during the secondary response after 10 days than with a larger dose.