Total human Ig in human/Balb chimera. PBMC from BCLL patients in different stages of disease and from normal donors were transplanted into conditioned Balb/c mice (4 patients in stage 0, 10 in stage I to II, six in stage III to IV, and 3 normal donors). Human antibody production was measured 2 weeks after transplantation by ELISA. *Significant in F test.