When portions of the cytoplasm of fibroblasts cultured from mouse embryo tissues are irradiated with heterochromatic microbeams of ultraviolet light. lymphocytes arc attracted (Lymphotaxis) to the injured areas. The lymphocytes approach in the "hand mirror'' shape characteristic of tissue cultures. On reaching the fibroblast, pseudopodia shoot out to "lick" the wound and then the lymphocyte "worms" its way across the cell. Only one lymphocyte contacts a fibroblast but the Same one may make several passes. It is postulated that lymphocytes are cleaning the wounded area of undesirable irradiation products and/or applying heding substances to the wounded fibroblast.
Irradiation of lymphocytes in portions of the cytoplasm fails to evoke responses from nearby lymphocytes. Instead, the cytoplasm whixls .around the nucleus as if the irradiation products can not leave the cell, resulting in convulsions and death.
A technique is described by which relatively pure cultures of lymphocytes may be obtained from leukocyte cultures by selectively killing all granular leukocytes with excessive exposure to microbeams of ultraviolet fight. Lymphocytes are harvested and introduced into fibroblast cultures to study experimental lymphotaxis.