Immunoglobulin Production in Synchronized Cultures of Human Hematopoietic Cell Lines

Abstract

The production of immunoglobulin in the various metabolic stages of the generation cycle of cultured human lymphocytoid cells was investigated by the use of synchronized cultures. The cells were synchronized at the boundary of the G1 and S periods by treatment with excess thymidine and the cells harvested at different time intervals after the release from the thymidine treatment were examined for their immunoglobulin content. The content of immunoglobulin was determined for individual cells by treating cell smears with ¹²⁵I-labeled anti-immunoglobulin antibody, submitting them to radioautography and counting the silver grains on individual cells. Cell smears were also stained with fluorescein-conjugates of antiimmunoglobulin antibodies. Although the immunoglobulin content of individual cells differed greatly even in the same harvest of a synchronized culture, there was a general change during the course of the generation cycle. The immunoglobulin level increased rapidly after the release of the thymidine blockage and reached its peak in the early portion of the S period. It then decreased gradually through the late S and G2 periods and reached its lowest level in the mitotic period. The second phase of increase which was observed after the mitotic burst indicated the synthesis of immunoglobulin by the cells of the second generation in the G1 and early S periods. Further studies on the secretion of the immunoglobulin are required to obtain an overall pattern of the immunoglobulin synthesis.