Specificity of antigen recognition by normal thymus cells in nude mice

If injected with normal thymus cells from BALB/c or BALB/c-Ig^b, nude mice from a stock which is partially backcrossed to BALB/c make antibodies to many antigens to which untreated nude mice do not respond. Anti-Ig^b can be made if the thymus donor is BALB/c, but not if the thymus donor is BALB/c-Ig^b. If cells from both donor strains are injected, a response is obtained which shows that the unresponsiveness of recipients of BALB/c-Igb cells is not due to tolerance of donor antigens.