[Changes in the proliferative activity of L cells in response to immune sera]

The influence of heterologous anti-L-serum and IgG isolated from it on the proliferative activity of L cells was studied with the use of the 3H-thymidine incorporation technique. High concentrations of the antiserum were shown to suppress, while low concentrations to stimulate the proliferative response of L cells. Both high and low concentrations of IgG were found to stimulate L cells. This indicates that stimulation of the growth of L cells is caused by antibody fraction. The presence of a greater number of antibodies, as well as of some serum components, is required for the development of the inhibitory effect. The line of the effect may be changed by supplementary actions. The proliferative activity of the whole population of L cells and descending cells was evaluated from the total 3H-thymidine incorporation.