Journal of the Reticuloendothelial Society最新文献

A factor in antigen- or mitogen-stimulated murine spleen cell culture supernatants that induces macrophage-mediated tumor cytotoxicity was characterized physicochemically. Although activity was eluted from Sephadex G-100 columns in a region corresponding to a MW of 55,000, rechromatography of the first and second halves of the eluted peak resulted in two separate peaks, corresponding in location to the first and second halves of the original peak. This shows that the original peak comprises two activation factors of slightly different MW. In contrast, electrofocusing experiments designed to assure that the isoelectric position had been reached by the end of the run showed a single isoelectric point of pH 5.8, with no sign of charge heterogeneity. Denaturation studies showed rapid loss of activity at 60 degrees C, stability over a pH range of 5 to 10, loss of activity at pH 4.0, and loss of two-thirds of the activity in 6 M urea. The number of criteria by which this lymphokine has now been characterized should suffice to distinguish it from other lymphokines evaluated by similar methods.

The translocation of Percoll microspheres (mean diameter 20-30 nm) from the intestinal lumen through the epithelial layer to internal organs was examined in suckling mice using transmission electron microscopy. Repeated administration of this material by gavaging for 7 consecutive days resulted in a heavy particle load of vacuolated enterocytes. A limited amount of Percoll was transported to the subepithelial tissue of both the villous mucosa and Peyer's patches where microspheres were found endocytosed, predominantly by macrophages. Even smaller numbers of particles reached mesenteric lymph nodes and, occasionally, milky spots of the omentum. Minor Percoll aggregates were easily found in Kupffer cells of the liver, indicating hematogenous translocation. Small numbers of particles were regularly detected in perivascular macrophages of the thymic cortex, which are in close contact with surrounding lymphocytes. We conclude that the thymic cortex is not totally inaccessible to particulate matter of the intestinal content.

The binding of IgG-coated erythrocytes to Fc receptors on both a lymphoblastoid and a macrophage-like cell line resulted in a decrease in thickness of the polyanionic, extracellular glycocalyx (cell coat) as determined by electron microscopic histochemistry. This decrease showed no correlation with ligand-binding sites and was considered to be a generalized extramembrane effect. Pretreatment of the cells with trypsin or neuraminidase produced decreases in thickness similar to those observed following ligand binding. The results suggest a possible role for enzymatic cleavage of extracellular constituents by morphologically and functionally different cell types and may represent an event common to cell-surface recognition.

Interaction between free airway cells (FAC) and lung fibroblasts was studied in a sheep model of asbestosis. Three groups of six sheep each received, respectively, by repeated intratracheal instillations, saline (control), 328 mg (low dose), and 2282 mg (high dose) of UICC chrysotile B asbestos. Sixteen months after the first instillation, FAC obtained by segmental bronchoalveolar lavage (BAL) of sheep in each group were incubated for various intervals, and the effect of their culture supernatants (FAC-SN) on human embryonic lung fibroblast proliferation was determined. FAC-SN from control animals stimulated thymidine (3H-TdR) incorporation by lung fibroblasts two- to threefold compared to untreated cultures. Maximal stimulation was observed at 48 hr and was correlated with a significant increase of the fibroblast population at 72 hr. FAC population from control sheep consisted primarily of macrophages (79%) and lymphocytes (15%), and separation of these two cell populations indicated that only macrophages produced the fibroblast-stimulating activity. Production occurred within 1 hr of incubation and was maximal between 2 and 4 hr. This activity was nondialyzable and stable at 56 degrees C for 30 min, but was destroyed at 80 degrees C and low pH. Moreover, FAC-SN from sheep exposed to asbestos stimulated 3H-TdR incorporation by fibroblasts five- to sixfold compared to two- to threefold for control FAC-SN. This activity may modulate fibrogenesis and may be involved in the eventual fibrogenic response to asbestos.

The effects of acute treatment with the phospholipidosis-inducing agent chlorphentermine (CP) on alveolar macrophage (AM) function heretofore have not been investigated. We evaluated the effects of acute CP treatment on the functional status of AM by comparing Fc receptor (FcR) and "nonspecific substance receptor"-mediated particle binding and phagocytic activities, as well as the plastic substrate adherence characteristics of AM lavaged from control (CONT-AM) and CP-treated (CP-AM) rats. Acute CP treatment caused an impairment in AM phagocytosis and binding of sheep red blood cells opsonized with immunoglobulin G (IgG). Although CONT-AM and CP-AM avidities for tanned human red blood cells were indistinguishable, phagocytosis of these particles by CP-AM was diminished in a manner similar to that found for FcR-mediated phagocytosis. Analyses of the distributions of test particles in phagocytizing CONT-AM and CP-AM indicated that the phagocytic activity of a subset of CP-AM was compromised by drug treatment. Populations of CP-AM were also found to be less adherent in a plastic substrate adherence assay verified with a poorly adherent AM population. Unlike studies involving chronic CP-treatment, our studies indicate acute CP administration results in an impairment in AM phagocytic activity and a reduction in FcR-mediated particle binding.

The role of bacterial endotoxin in the expression of human monocyte cytotoxicity was studied. Endotoxin contamination of all reagents and steps of the experimental procedure were assessed by the limulus amebocyte lysate (LAL) assay. Peripheral blood monocytes were separated by adherence, and cytotoxicity was measured as [3H]-thymidine release from prelabeled mKSA-TU5 murine target cells in a 48-hr assay. Human monocytes expressed appreciable levels of spontaneous cytotoxicity under LAL- conditions irrespective of the serum source employed (LAL- or LAL+ fetal bovine serum, FBS, or LAL- human cord serum, HCS). HCS gave the highest cytotoxicity levels and LAL- FBS the lowest. Polymyxin B (10 micrograms/ml), which inhibited endotoxin-induced gelation of LAL and activation of mononuclear cells for procoagulant activity, did not affect the expression of spontaneous monocyte cytotoxicity with all three sera used. Three preparations of endotoxin used in the present study (Escherichia coli, S. typhosa, S. minnesota) caused small increases in monocyte killing in micrograms per milliliter concentrations only in 5 of 19 experiments performed. Human lymphoblastoid interferon (LAL-) and phytohemagglutinin-elicited lymphokine supernatants (LAL-) enhanced the tumoricidal activity of human monocytes under LAL- conditions and were not affected by Polymyxin B. It is concluded that exposure to endotoxin is not a prerequisite for the expression of spontaneous cytotoxicity by human blood monocytes.

We have studied the pattern of membrane binding site redistribution, movement, and reappearance in polarized and nonpolarized human neutrophils using fluorescein and rhodamine-labeled lectins as probes. In suspension, polymorphonuclear leukocytes (PMN) were spherical and displayed a random array of recognition sites for all of the probes. PMN polarized in suspension by 10(-6) M N-formyl-L-methionyl-L-phenylalanine (f-Met-Phe), and PMN attached to substrate accumulated the bound lectin recognition site complex at the uropod (for Con A; 92.0 +/- 0.2% of cells and 91.3 +/- 9.8% of cells, respectively). Glutaraldehyde fixation of neutrophils oriented in a chemotactic gradient prior to lectin addition revealed the innate unbound recognition site array. Unbound Con A recognition sites were clustered at the front of 74.7 +/- 0.8% of cells in a "headlight" pattern, but binding sites for other lectins were distributed randomly around the polarized cell. When bound Con A complexes are swept to the tail of the polarized living PMN, "new" unbound Con A binding sites appear at the front of the cell. Neither cycloheximide nor KCN nor colchicine interferred with new binding site appearance. Cytochalasin B and sodium iodacetate prevented PMN polarization and interfered with appearance of new receptors. This suggests that these fresh sites are uncovered, previously cryptic binding sites rather than newly synthesized structures. Lectin binding site topography and movement are related to the functional state of the PMN. Since both Con A and certain bacteria bind to mannose derivatives, we postulate that the "headlight pattern" and uncovering of fresh binding sites aid the PMN in engulfing organisms as the phagocyte moves forward.

Mouse spleen cells treated with the Fc receptor ligands mouse IgG2b and human IgG, followed or not by a second antibody, exhibit different patterns of redistribution. In the work reported here we have examined the redistribution of Fc receptors (FcR) after binding of aggregated mouse IgG2b (Alg) or of Alg followed by anti-lg. We were particularly interested in learning whether binding of isologous Alg to FcR is followed by significant redistribution and shedding of Alg-FcR complexes. Mouse IgG2b alone will not induce capping even after 60 min at 37 degrees C. Human IgG induces some capping with minor shedding of complexes. Human IgG followed by anti-IgG readily induces capping by 15 min on 70% of the cells. This treatment also induces capping by 60 min at 20 degrees C on about 80% of the cells with a moderate degree of shedding of complexes. This is in agreement with the concept that the crosslinking required for FcR capping can be best induced with a second antibody. It is of interest, however, that heterologous IgG, unlike isologous, can induce a modest degree of capping and slight shedding even without the second antibody, suggesting that some crosslinking occurs with heterologous IgG.

The human macrophage-like cell line, U937, produced significant amounts of prostaglandin (PG) E2 when incubated with exogenous arachidonic acid (AA). The synthesis of PGE2 was completely inhibited by pretreatment with indomethacin (20 micrograms/ml). Another major metabolite, unidentified, which was released during incubation with AA, was not inhibited by indomethacin, but was decreased by nordihydroguaiaretic acid (NDGA) (10(-5)M) or BW755C (10(-4)M). These results confirm the presence of cyclooxygenase and perhaps lipoxygenase activities in this macrophage-like cell line. Challenge of U937 cells with zymosan, opsonized zymosan, phorbolmyristate acetate (PMA), heat-aggregated human IgG (AHG), or calcium ionophore A23187 failed to stimulate synthesis and release of either PGE2 or the above mentioned metabolite. The inability of U937 cells to release endogenous AA from cell lipid for PG synthesis constitutes an important functional difference between these cells and normal macrophages.

Human monocytes were stimulated by lectins to release prostaglandin and other factor(s) that induce bone resorption in vitro. High concentrations of indomethacin failed to inhibit production by stimulated monocytes of most of the bone-resorbing activity. This activity was retained in culture supernatants after extensive dialysis. These data demonstrate that monocytes are capable of the simultaneous production of prostaglandins and nondialyzable bone-resorbing factor(s). This (these) factor(s) may mediate localized bone resorption associated with certain chronic inflammatory diseases.