Simultaneous development of antibody-dependent cellular cytotoxicity (ADCC) and natural killer (NK) activity in irradiated mice reconstituted with bone marrow cells

Spleen cells from irradiated, bone marrow-reconstituted mice were tested for their ability to mediate antibody-dependent cellular cytotoxicity against P815 target (ADCC-P815), ADCC against sheep red blood cells (ADCC-SRBC), and natural killer (NK) activity judged as YAC-1 lysis at different times after bone marrow reconstitution. Donor-derived ADCC-P815 effectors were found to appear in the spleens 10-12 days after bone marrow reconstitution simultaneously with the appearance of donor-derived NK cells. NK cells recently derived from bone marrow are known to express the Thy-1 antigen; the phenotype of the "early" ADCC-P815 effectors was found to be the same as that of NK cells, i.e., Thy-1+, asialo-GM1+. These data suggest that ADCC-P815 effector cells belong to the NK cell population. ADCC-SRBC, in contrast to ADCC-P815 and NK activity, was already high on Day 7 after bone marrow reconstitution. However, it was mediated partly by recipient-derived effectors. ADCC-SRBC effectors were characterized to be different from ADCC-P815 effectors.