Mammalian Phagocytes Research Articles

The Role of Lysosomes in Molluscan Inflammation1

Phagocytosis and related phenomena represent integral features of inflammation in all metazoans. Reviewed herein are the results of studies directed at understanding the role(s) of lysosomal enzymes synthesized and released from circulating hemocytes, especially granulocytes, of gastropods and bivalves as a result of challenge with exogenous, nonself materials. From what is known, most of the mechanisms underlying this inflammation-associated process parallel those of mammalian macrophages; however, immunoglobulins and most probably components of complement are not involved. The required energy for phagocytosis in molluscs appears to be derived from glycolysis alone. Furthermore, nitroblue tetrazolium reduction and the myeloperoxidase-H2O2-halide antimicrobial system, both characteristic of mammalian phagocytes, appear to be absent in molluscs. It is concluded that by studying phagocytosis by molluscan hemocytes, a great deal can be learned about the evolution of inflammatory response and its constitutent elements.

Serospecificity and opsonic activity of antisera to Legionella pneumophila.

A high-molecular-weight surface component (F-1 fraction) has been isolated from the four serogroups of Legionella pneumophila. Antibody raised against live organisms was found by microagglutination assay to be specific for the homologous serogroup. Agglutinating activity of antiserum was markedly diminished after absorption with the homologous, but not heterologous, F-1 fraction. In addition, it was found that L. pneumophila organisms were not interiorized by rat alveolar macrophages or mouse peritoneal macrophages in the absence of antiserum, whereas homologous antiserum effectively opsonized the organisms. The opsonizing activity of serogroup-specific antisera was eliminated by absorption of the antisera with the homologous, but not heterologous, F-1 fraction. These data indicate that the serogroup-specific antigen of L. pneumophila resides in the F-1 fraction and that antibody to the F-1 fraction is required for phagocytosis of L. pneumophila by mammalian phagocytes.

Aspects of substrate utilization and energy requirement during molluscan phagocytosis

Unlike the case of mammalian phagocytes, there is no increase in oxygen consumption by hemolymph cells of Mercenaria mercenaria actively phagocytosing Bacillus megaterium. The utilization of glucose and glycogen, coupled with the production of lactate and no increase in oxygen utilization, by M. mercenaria cells actively engaged in phagocytosis indicates that glycolysis is the energy-providing pathway. This conclusion is strengthened by the fact that KCN does not inhibit phagocytosis. Nitroblue tetrazolium reduction characteristic of mammalian phagocytes is absent in M. mercenaria hemolymph cells. The myeloperoxidase-H 2O 2-halide antimicrobial system of mammalian phagocytes is absent in hemolymph cells of M. mercenaria.

Ion movement across leukocyte plasma membrane and excitation of their metabolism.

A PERTURBATION of the molecular organisation of the surface membrane of mammalian phagocytes leads to significant modifications of their metabolism and functions1,2. These modifications include a rapid increase of oxygen uptake, of glucose oxidation by the hexose monophosphate pathway (HMP) and of hydrogen peroxide production1–3; an enhanced turnover of membrane phospholipids4 and a degranulation with extrusion of lysosomal proteins from cells5,6. The importance of this functional response of phagocytes is particularly evident when the alteration of their surface properties is caused by interaction with bacteria, which, on being engulfed, can be killed and digested by the toxic agents (for example, H2O2, superoxide anions, cationic proteins and hydrolytic enzymes) produced and/or discharged into the phagocytic vacuole6–9.

Comparative biochemistry of phagocytizing insect hemocytes

1. 1. The respiratory increment associated with phagocytosis by mammalian leukocytes is absent in Blaberus craniifer hemocytes. 2. 2. The glycolytic pathway provides energy for particle engulfment in both mammalian leukocytes and B. craniifer phagocytes. 3. 3. Hexose monophosphate pathway activity of roach hemocytes, unlike mammalian cells, is not stimulated by phagocytosis. 4. 4. Nitroblue tetrazolium reduction, characteristic of mammalian phagocytes, is absent in B. craniifer cells. 5. 5. B. craniifer hemocytes utilize antimicrobial systems other than the myeloperoxidase-H 2O 2-halide system of mammals.

EFFECT OF OPSONINS ON PHAGOCYTOSIS AND KILLING OF SALMONELLAE BY AMOEBA PROTEUS, AND THE USE OF PHAGE P22 TO ELIMINATE SURPLUS EXTRACELLULAR BACTERIA.

SummaryMammalian serum opsonins have been shown to possess moderate power to promote phagocytosis of Salmonella enteritidis by Amoeba proteus, but serum opsonins had no measurable effect on the rate of intracellular killing of these bacteria or of Salmonella typhimurium. The survival time of opsonised salmonellae after phagocytosis by amoebae was considerably longer than would be expected if similar bacteria were to be ingested by mammalian phagocytes. The possible effect of temperature on intracellular bactericidal mechanisms is discussed.Also described is a technique in which a lytic mutant of phage P22 was used to eliminate residual extracellular salmonellae from washed amoebae after a standard period of phagocytosis.