A Histochemical Study of Phagocytic and Enzymatic Functions of Rabbit Mononuclear and Polymorphonuclear Exudate Cells and Alveolar Macrophages

Abstract

Summary and Conclusions The effect of particle ingestion on the activity of certain enzymes of mononuclear (MN) and polymorphonuclear (PMN) exudate cells and alveolar macrophages (AM) was evaluated by quantitative and semiquantitative histochemical techniques. The particles were yeast and chicken red blood cells in the presence of immune serum, and polystyrene in the presence of normal serum. The enzymes were acid and alkaline phosphatase, esterase and succinic dehydrogenase—enzymes probably more concerned with metabolic than with digestive phenomena. The period of ingestion usually varied from 10 to 40 min, in tubes attached to a drum rotating at 6 rpm. Phagocytes containing particles were found to have the same amount of histochemically detectable enzymes as adjacent phagocytes on Mylar strips that had not ingested particles. In other words, the ingestion of particles was not associated with an increased content of enzymes. Biochemical studies on the acid phosphatase of frozen and thawed MN and PMN that had ingested various particles confirmed this conclusion. However, manometric studies under similar conditions showed that the phagocytic process increased the respiration of viable cells. This suggests that their metabolic enzymes, although unchanged in amount, were utilized more fully. The effect of particles on the enzymes of phagocytes was also evaluated over longer periods of mutual association. For this purpose rabbit mononuclear exudate cells were allowed to ingest yeast particles and then were cultured along with controls in 98% autologous serum, a method adopted from Dr. Y. T. Change of the National Institutes of Health. Zero- and 48-hr Mylar strip preparations then were made from these cell cultures for quantitative histochemical evaluation. Not all experiments were successful, but in those that were, the 48-hr cell preparations containing yeast showed a significant increase in the number of MN with high esterase and acid phosphatase contents. This seemed to be associated with digestion of the yeast particles. Although other interpretations are possible, we feel that the increased enzyme content of these cells was due to an adaptive response to the intracellular presence of particles. The above findings are consistent with the following concept: a) An initial protoplasmic excitation, brought about by collision with particles and/or their actual ingestion, results in an increase in the oxygen consumption of intact cells. Such phagocytes are activated, in that they ingest the particles more readily and probably have increased motion and pseudopod formation. Their enzymes are not increased in amount, but seem to be utilized nearer their full capacity and may have a different distribution within the cell. b) This excitatory response initiates and merges with protoplasmic adaptation which is a more lasting response on the part of the phagocyte to ingested material and other irritants. It is expressed by an increase in certain enzymes, and specific and nonspecific changes in the phagocytic, bactericidal and digestive powers of the cell. These two phases of phagocytic activation may be crucial to the host's defense against infectious disease.