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To assess the ability of the sarcoidal granuloma to modify peripheral mononuclear cell function, we assayed the culture supernatants of cutaneous granulomata for modulators of monocyte locomotion. The supernatants of granulomata from each of 11 patients contained a cell-directed inhibitor of monocyte leukotaxis. No inhibitory activity was detected in the supernatants of histologically normal skin biopsies. The inhibitor acted only on monocytes, possessed a molecular weight of 230,000 daltons, and was clearly distinct from migration inhibition factor (MIF), leukotactic lymphokines, and immunoglobulins. A physicochemically and functionally indistinguishable inhibitor was present in patient plasma. Production of the inhibitor by the granuloma required active protein synthesis. Culture supernatants also contained MIF and a leukotaxin inactivator. These observations indicate the potential of the sarcoidal granuloma to exert local and, perhaps, systemic regulation of inflammatory processes.

Sarcoidosis is an immunopathogenic disorder of uncertain cause. Because the regulation of monocyte mobilization and function may be critical to granuloma formation in this disease, we evaluated production of the cell-directed inhibitor of monocyte leukotaxis (CDI-MLx) by peripheral blood and bronchoalveolar lavage mononuclear cells from these patients. Cells obtained from either source during clinically active disease spontaneously produced this leukotactic regulator in vitro in amounts comparable to those achieved with maximal mitogenic stimulation of normal cells. Plasma leukotactic inhibitory activity and spontaneous inhibitor production were significantly associated. Plasma inhibitory activity and CDI-MLx production were normal in patients whose disease was inactive. Spontaneous production continued for at least 7 days in vitro and could not be attributed to alterations in the absolute numbers of specific mononuclear cell populations. Partitioning of peripheral blood mononuclear cells by a combination of E-rosetting and immunoadherence techniques indicated, however, that CDI-MLx was produced by a subpopulation of natural killer-like cells that formed E-rosettes and bore the OKMI and Leu 7 membrane antigens.

The leukotactic responsiveness of human peripheral blood monocytes is regulated by the cell-directed inhibitor of monocyte leukotaxis, CDI-MLx. Normal peripheral blood mononuclear cells elaborated CDI-MLx in vitro in response to soluble and cell-associated antigens; concanavalin A and pokeweed mitogen induced production of the inhibitor while phytohemagglutinin and staphylococcal protein A were without effect. By erythrocyte rosetting and immunoadherence, the CDI-producing cell had the phenotype, E-rosette+, OKMI+, and Leu 7+, and thus appeared related to natural killer cells. PBMC and plasma CDI-MLx had similar molecular weights (230,000) and showed similar heterogeneity on chromatofocusing with peaks of activity at pH 5.8 and 5.25. CDI-MLx was immunologically distinct from immunoglobulins, did not inactivate preformed leukotaxins, and was distinct from other lymphokines known to modulate monocyte locomotion.

The leukotactic responsiveness of human peripheral blood monocytes is regulated by the cell-directed inhibitor of monocyte leukotaxis, CDI-MLx. The actions of CDI-MLx on normal monocytes in vitro were abrogated by co-incubation with inhibitors of cyclooxygenase and thromboxane synthetase with indomethacin and dazmegrel (UK-38,485) being most active. The actions of CDI-MLx were mimicked by the thromboxane A2 analogue, U-46619, and by 12-HHT with half-maximal inhibition observed at 10(-10) M; PGE2 was 1000-fold less active. SQ 29,548, a thromboxane A2 receptor antagonist, blocked the effects of CDI-MLx, U-46619, and 12-HHT. Production of PGE2 and thromboxane B2 by purified monocytes was stimulated by CDI-MLx and this effect was also blocked by indomethacin, dazmegrel, and dazoxiben. These data suggest a major regulatory role for thromboxane synthetase products in human monocyte leukotaxis.

Because the accumulation and activation of mononuclear phagocytes are critical to the host response to intracellular microbial pathogens, we evaluated mechanisms of peripheral monocyte leucotactic regulation in leprosy. Plasma from 53 of 67 patients was found to inhibit the locomotion of normal human monocytes. Neither the prevalence nor the magnitude of plasma leucotactic inhibitory activity correlated with disease histology or duration, type or duration of chemotherapy, or history of erythema nodosum leprosum. Plasma leucotactic inhibitory activity resided principally in a non-immunoglobulin, cell-directed inhibitor of 230,000 daltons molecular weight. Fractionation of plasma from patients with lepromatous leprosy revealed an additional, immunoglobulin-containing inhibitor of approximately 400,000 daltons weight, possibly an IgG-IgA immune complex. Production of leucotactic inhibitors by unstimulated and concanavalin A-stimulated peripheral mononuclear cells was normal; however, cutaneous explants from these patients spontaneously produced the 230,000 dalton leucotactic inhibitor in vitro. The ability of the lesions of leprosy to impede monocyte traffic may be an important pathogenetic mechanism.