Effects of negative pi mesons on immune responses in mice

Spleen cells from normal or preimmunized mice were exposed to graded doses of peak pions or 300-kVp x rays in vitro and then cultured in heavily irradiated mice to determine antibody production against sheep erythrocytes. The RBE for the primary antibody response was 1.46. Equal suppression of secondary responses was seen with both pions and x rays. When spleen cells were irradiated 1, 3, or 5 days after antigen injection, developing immune responses became less sensitive to pions than to x rays. Because T-cell activity (needed for the antibody response) is also implicated in tumor immunity, antitumor immune responses might not be more sensitive to pions than the response used; also, pions might not impair ongoing autochthonous immune responses more than conventional radiation modalities do.