Antibody-dependent cellular cytotoxicity (K) and natural killing (NK) in B-suppressed germ-free nude rats.

The influence of the thymus and the possible requirement for surface immunoglobulin expression for the development of K and NK activity were assessed in rats. This species was chosen in preference to mice as they show good levels of K-cell activity. Studies were carried out in athymic (rnu/rnu) rats some of which were treated from birth with rabbit anti-rat IgM antibody to suppress B-cell development. The results indicate that normal levels of both K and NK activity develop in the spleens of 6-8-week-old athymic rats, which do not contain cells expressing surface membrane immunoglobulin. While K and NK cells show characteristics of the lymphoid lineage, neither the thymus nor surface membrane immunoglobulin expression appears to be required for development of normal levels of these cytolytic activities.