Castration increases the regulatory T-cell population but does not alter MOG-specific suppression. (A-C) Splenic regulatory T-cell populations were analyzed by flow cytometric expression of CD4⁺CD25⁺FoxP3⁺. Mice treated with BMT and castration displayed a significantly higher proportion and cellularity of FoxP3⁺ T regulatory cells than mice treated with BMT only. (D,E) Direct suppression assays on splenocytes were used to analyze the generalized (CD3e/CD28 stimulated) and specific (MOG_35-55 stimulated) suppressive capabilities between mice treated with BMT or BMT in combination with castration. Although Cx/BMT mice had proportionally fewer FoxP3⁺ cells in their CD4⁺CD25⁺ population, they were equally capable of suppressing the generalized and MOG-specific activation of splenocytes. (F) Spleen cells from C57Bl6 mice adoptively transferred with MOG_35-55–specific cells proliferated strongly in the presence of all antigens. Results are expressed as mean plus or minus SEM of 5 to 10 mice from 2 or more independent experiments, unless otherwise stated. *P < .01 versus BMT only.