The primary antibody responses of spleen cell cultures were investigated for LEC rats, a mutant strain of LEA rats, which are known to develop spontaneous hepatic injuries. Compared to LEA rats, LEC rats were significantly low in responding not only to a T-dependent antigen, SRBC, but also to a B-cell stimulant, LPS. The antibody responses of LEC rats having fed a diet deprived of Cu metal (LEC/Cu-) showed values intermediate between LEA and LEC rats, thus suggesting a recovery from an immuno-deficient state as well as liver damage in LEC/Cu- rats. The addition of LEA bone marrow cells prior to culture to LEA or LEC spleen cells, strikingly enhanced the antibody response, whereas LEC bone marrow cells were totally ineffective, or sometimes depressed the response. These results have suggested a newer concept for a possible correlation between liver-dysfunction and bone marrow cell-functions in LEC rats, both encoded by autosomal genes.