In Vitro Evidence For A Spleen-Derived Macrophage Suppressor Factor

Date of Graduation

Spring 1982


Master of Science in Biology



Committee Chair

Richard Myers


Splenectomized mice are more resistant than normal mice to infection by Listeria monocytogenes. This appears to be due to a splenic suppressor factor which inhibits phagocytosis by macrophages. An in vitro assay was developed which used monolayer cultures on microscope cover slips and direct microscopic examination to quantify two parameters of phagocytosis: 1) percentage of phagoxytic cells, and 2) mean number of bacteria per phagocytic cell. Normal mouse peritoneal exudate cells (PEC) were cultured with normal mouse plasma (NMP) or splenectomized mouse plasma (SMP). There was no significant difference between the NMP and the SMP cultures in the percentage of phagocytic cells, but NMP reduced the number of intracellular Listeria per phagocyte by 33 percent. This result correlates well with the results of in vivo assays comparing normal and splenectomized mouse PEC activity. When NMP was separated by pressure ultrafiltration, the low (less than 10,000) MW fraction suppressed both parameters of phagocytosis, when compared with the high MW fraction. Supernatant medium from cultures of spleen cells also suppressed both parameters of phagocytosis; 1:10 dilution of the supernatant fluid did not alter the degree of suppression, indicating that the factor is active in relatively low concentrations. This in vitro assay method may be used for further investigation and characterization of this spleen-derived macrophage suppressor factor (MSF).

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