The effects of drugs on monocytic fusion in vivo

Macrophages: current views on their differentiation, structure, and function

Macrophages are large mononuclear phagocytes that represent the major differentiated elements of the mononuclear phagocytic system. They arise from distinct progenitors in the bone marrow, and their immediate precursors, the monocytes, emigrate from the vascular compartment into many tissues and organs where they develop into mature macrophages. The latter display diverse morphological and functional characteristics, depending on the environmental stimuli that they receive. This phenotypic heterogeneity is, therefore, the final consequence of a series of down-regulation of some cellular processes and the up-regulation of others. The kinetics of the production of macrophages and their participation in various physiological and pathological phenomena is the subject of this review.

Tocainide suppression of immune-complex-mediated dermal inflammation: comparison with prostaglandin E1

Local anesthetic agents have been shown to alter a variety of polymorphonuclear leukocyte (PMN) functions and may be useful as anti-inflammatory agents. We compared the anti-inflammatory effects of therapeutic doses of the recently released local anesthetic-antiarrythmic drug tocainide to pharmacologic doses of prostaglandin E1 (PGE1) on immune-complex-mediated dermal inflammation in female Sprague-Dawley rats. Intense dermal inflammation was produced using a classic reverse passive Arthus reaction, and the inhibition of PMN accumulation in the subdermis was quantitated in biopsy samples taken 2.5 hr after the reaction was initiated and the drug was given. Using a light microscope with a counting grid, biopsy sections were randomly sampled in a blinded fashion and an inflammation index equal to the ratio of PMNs to fibroblasts was determined for each animal. The mean inflammation index in 10 animals given 25 mg of tocainide (mean serum level = 14.6 micrograms/ml) was 9.3 +/- 1.2 (+/- SEM), which was significantly less than the index of 17.7 +/- 2.5 in 10 control animals (P less than 0.025). Similarly, the five animals that received either 500 or 250 micrograms of PGE1 had a significantly reduced index, with the effect of 250 micrograms PGE1 comparable to the effect of the tocainide. These findings suggest that therapeutic levels of tocainide reduce the accumulation of PMNs in immune-complex-mediated dermal inflammation; thus, local anesthetic agents may be useful in the treatment of certain inflammatory disorders.

Effect of lidocaine on the function of immunocompetent cells. II. Chronic in vivo exposure and its effects on mouse lymphocyte activation and expression of immunity

In vivo exposure of mice to lidocaine (0.25 mg/10 g body weight 4 times a day for 7 days) resulted in impairment of immunocompetent cell function. Spleen lymphocytes removed from animals immediately and 3 days after lidocaine exposure showed changes in their surface charge properties, inhibition of blastogenesis in response to concanavalin A and lipopolysaccharide, and inhibition of antigen-stimulated activation as measured by the mixed lymphocyte reaction. Lymphocytes from animals sensitized to keyhole limpet hemocyanin showed a significantly lower capacity to produce macrophage migration inhibitory factor 8 days after termination of exposure to lidocaine. Animals exposed to the drug were unable to accumulate an adequate number of immunocompetent cells at the site of challenge with a foreign substance (i.e. dextran), and the ability of the animals to destroy tumor cells nonspecifically and specifically was also impaired. The results indicated that chronic exposure to lidocaine resulted in impairment of lymphocyte function, even in the subsequent absence of the drug, and in significant changes in the expression of the immune response.

Hormonal effects on prevention or regression of atheroma

White Leghorn cockerels, fed either normal or cholesterol enriched food, were injected with saline, peanut oil, testosterone, oestradiol, progesterone, or oestradiol plus progesterone for 87 days. The ascending aortas, descending aortas and abdominal aortas were examined by light and electron microscopy and both qualitative and quantitative assessments made. The results were subjected to multivariate analysis. Cholesterol feeding increased lipid storage and round cell infiltration in the endothelium and intima, and both the degree of lipid storage and the amount of lumen obstruction was much greater in the abdominal aorta than in the ascending or descending aorta. Treatment with oestrogen plus progesterone, regardless of diet or site of action, caused a highly significant reduction in the percentage of normal cells of the endothelium. Those cockerels treated with oil, androgen and progesterone showed significantly less large foamy eosinophilic endothelial cells than those treated with oestrogen plus progesterone. The degree of round cell infiltration was increased by androgen and oestrogen, but not by oestrogen plus progesterone, when compared with both saline treated and oil treated controls. Cholesterol feeding caused a reduced percentage of normal endothelial cells. This was significantly enhanced by treatment with androgen, progesterone and saline. The effect of cholesterol feeding as a cause of a reduced percentage of normal, and an increased percentage of foamy eosinophilic endothelial cells, was significantly enhanced in the ascending aorta and the descending aorta but not in the abdominal aorta. The same site-dietary interaction was observed in the trend towards an excess of large clear cells over large eosinophilic cells in the intima. In spite of this the extent of plaque likely to cause obstruction as a result of this site-dietary interaction was increased only in the abdominal aorta. An unexpected treatment-site interaction was that progesterone had an enhanced effect, causing disruption of the internal elastic lamina of the ascending aorta but not of the descending or abdominal aortas. There was no evidence that diet or treatment increased the amount of acid esterase in the tissues, even though the chickens showed the expected species deficiency of this enzyme, but there was a significant relationship between the presence of lipid and the amount of acid esterase in the plaques of the abdominal aorta. Male albino Wistar rats were primed with peanut oil, oestrogen and triamcinolone before subcutaneous granulomas were induced by implanting cholesterol, and then treated with these substances for longer periods. Cryostat sections of the granulo

Macrophage polykarya

Multinucleated giant cells are commonly found in a wide variety of inflammatory reactions. They are formed at sites of tissue injury by fusion of freshly exuded monocytes, the rate of fusion being dependent on a range of extracellular and intracellular factors. Electron miscroscopy shows that the pooled components of the fused monocytes are not randomly dispersed in the syncytium, but are highly reorganized into a functioning unit. In addition, histochemical and biochemical profiles of cell populations containing these polykarya display a range of metabolic activities, including DNA synthesis, which, on occasions, is followed by successful mitotic division and the formation of polyploid daughter cells. Fusion results in the loss of some surface receptors which in turn interferes with the phagocytic performance of polykarya, which is generally less pronounced than their mononuclear precurses. In addition, polykarya are not as actively motile as macrophages although phenomena of contact inhibition are less obvious. On the other hand, the multinucleate giant cells display prominent exocytosis which may aid in the degradation of extracellular material. The properties of macrophage polykarya contrast with macrophage homokarya produced in vitro. The latter are actively phagocytic, do not synthesize DNA, and have a longer half-life than the syncytia produced in chronic inflammatory reactions. It may well be that the polykarya in such reactions are not true homokarya.

The differentiation of monocytes into macrophages, epithelioid cells, and multinucleated giant cells in subcutaneous granulomas. I. Fine structure

The morphological changes occurring in monocytes during their differentiation into macrophages, epithelioid cells, Langhans-type giant cells, and foreign-body-type giant cells were investigated in foreign-body granulomas induced by subcutaneous implantation of pieces of Melinex plastic. Analysis based on Adams's (1974) criteria for discrimination between the several types of cell of the monocyte line, showed that each type has a characteristic type of granule. Primary and secondary granules, numerous in the Golgi area of monocytes were generally found close to the cell membrane and decreased in number in maturing macrophages. This was accompanied by an increase in the number of microtubules. Mature macrophages show numerous characteristic macrophage granules, which are round (average diameter: 280 nm) and have a halo between the limiting membrane and granular matrix. Mature epithelioid cells have characteristic epithelioid cell granules, and multinucleated giant cells a heterogenous population of granules. Fusing macrophages generally have their Golgi areas facing each other, and also show a reduced thickness of the cell coat. The morphology of the multinucleated giant cell is closely related to the number of nuclei present. In Langhans-type giant cells, which generally have two to ten nuclei, a giant centrosphere with numerous aggregated centrioles is found. In transition forms between Langhans-type and foreign-body-type giant cells, which generally contain 10--30 nuclei, the centrioles show less aggregation. In the foreign-body-type giant cells, which generally have more than 30 nuclei, centrioles are virtually absent and never aggregated. These differences between the Langhans-type giant cells, the foreign-body-type giant cells, and the transition forms, support our previous finding that Langhans-type giant cells are the precursors of foreign-body-type giant cells.

Endocytosis and formation of macrophage polykarya: an ultrastructural study

Mononuclear phagocytes in foreign body granulomas become entrapped by the lamellipodia or enter the intracytoplasmic membranous labyrinth of macrophage polykarya. Evidence of membrane fusion was found in such instances and it is suggested that the internalisation of the mononuclear phagocyte is allied to the motility of the syncytium. This concept is also supported by the reports of other authors who emphasise the role of endocytosis in the formation of macrophage polykarya. The net effect of such a mechanism is growth of the syncytium.