SOME FACTORS AFFECTING THE YIELD OF THE MONOCYTOSIS-PRODUCING AGENT

Abstract

From Listeria monocytogenes cultured at 4 °C and at 37 °C, a lipid fraction called monocytosis-producing-agent (M.P.A.) was extracted. From the cells cultured at 4 °C, twice as much M.P.A. was obtained per unit of dry weight cells. M.P.A. obtained from cells cultured at 4 °C was as effective as the one isolated from cells grown at 37 °C in stimulating monocytes production in rabbits. The time of incubation at 4 °C was varied from 5 to 10 days without significant difference in cell yield. Extraction of M.P.A. was neither quantitatively nor qualitatively enhanced by sonic oscillations at 8000 cycles. Such treatment of dead cells for as long as 105 minutes failed completely to disintegrate the organisms. Further destruction of the cell walls by sonic oscillation or shaking with glass beads contributed little to the overall yield of M.P.A.