CELL-CYCLE KINETICS OF THE ACCUMULATION OF HEAVY AND LIGHT-CHAIN IMMUNOGLOBULIN PROTEINS IN A MOUSE HYBRIDOMA CELL-LINE

Rates of accumulation of immunoglobulin proteins have been determined using flow cytometry and population balance equations for exponentiall y growing murine hybridoma cells in the individual G(1), S and G(2)+M cell cycle phases. A producer cell line that secretes monoclonal antib odies, and a nonproducer clone that synthesizes only kappa-light chain s were analyzed. The pattern for the kinetics of total intracellular a ntibody accumulation during the cell cycle is very similar to the prev iously described pattern for total protein accumulation (Kromenaker & Srienc 1991). The relative mean rate of heavy chain accumulation durin g the S phase was approximately half the relative mean rate of light c hain accumulation during this cell cycle phase. This indicates an unba lanced synthesis of heavy and light chains that becomes most pronounce d during this cell cycle phase. The nonproducer cells have on average an intracellular light chain content that is 42% lower than that of th e producer cells. The nonproducer cells in the G(1) phase with low lig ht chain content did not have a significantly higher rate of light cha in accumulation relative to other G(1) phase nonproducer cells. This i s in sharp contrast to what was observed for the G(1) phase producer c ells. In addition, although the relative mean rate of accumulation of light chain was negative for G(2)+M phase nonproducer cells, the magni tude of this relative mean rate was less than half that observed for t he producer cells in this cell cycle phase. This suggests that the mec hanisms that regulate the transport of fully assembled antibody molecu les through the secretion pathway differ from those which regulate the secretion of free light chains. The results reported here indicate th at there is a distinct pattern for the cell cycle dynamics of antibody synthesis and secretion in hybridomas. These results are consistent w ith a model for the dynamics of secretion which suggests that the rate of accumulation of secreted proteins will be greatest for newborn cel ls due to an interruption of the secretion pathway during mitosis.