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Mast cells play a critical role in allergic airway responses via IgE-specific activation and release of potent inflammatory mediators. In the present study, we have isolated and characterized primary mast cell lines derived from the upper airways of normal mice. The primary mast cell lines were grown and maintained by incubation with interleukin-3 (IL-3) and stem cell factor (SCF) and shown to be c-kit (SCF receptor) positive by flow cytometry. Subsequently, we examined the proliferation of both airway and bone marrow derived mast cell lines in response to inflammatory and hematopoietic cytokines, including SCF, IL-1, IL-3, interferon-gamma, IL-4, and IL-10. The results from the pulmonary mast cell lines were compared with those from bone marrow derived mast cells. Pulmonary mast cell lines were capable of proliferating in response to IL-3, IL-4, IL-10, and SCF, whereas the combination of SCF with the other cytokines did not increase the response over SCF alone. In contrast, the bone marrow-derived mast cells proliferated strongest to SCF or IL-3, but only modestly to IL-4 and IL-10. Furthermore, the combination of SCF with IL-3, but not the other cytokines, exhibited an increase in bone marrow-derived mast cell proliferation. Cytokine-specific stimulation of histamine release in the airway-derived and bone marrow-derived mast cells showed parallel results. SCF was the only cytokine shown to induce substantial histamine release. However, when certain nonhistamine releasing cytokines were combined with SCF, a synergistic increase in histamine release was induced in upper airway, but not bone marrow-derived mast cells. The results of these studies suggest that cytokines differentially modulate induction of proliferation and degranulation of bone marrow and upper airway-derived mast cells and may further indicate a cytokine activational cascade in tissue mast cells.

A well defined model of T cell-mediated hypersensitivity-type granulomatous inflammation induced by Schistosoma mansoni eggs was used to assess the role of IL-4 and IFN-gamma in granuloma development. Synchronized pulmonary granulomas were induced and isolated from S. mansoni-infected mice during vigorous (8 wk) and modulated (20 wk) stages of the disease. The sequential production of IL-4 and IFN was determined and related to temporal changes in granuloma macrophage production of IL-1, TNF, and superoxide anion (O2-). During the vigorous stage, IL-4 was produced on days 1 and 2 of granuloma formation, whereas IFN was released in greatest amounts on days 4 to 8. The peak of IL-4 occurred in a window between the peak of IL-1 (1 day) and maximal TNF production (8 to 16 days). Maximal O2- release tended to parallel IFN production. During the modulated stage when the inflammatory response is attenuated, IL-4 production was dramatically reduced as were levels of IL-1 and TNF, but IFN production persisted and maximum O2(-)-producing capacity was only delayed in onset. mAb specific for IL-4 and IFN were used to examine the effect of in vivo depletion of these cytokines on granuloma development. Administration of a single 1.0-mg dose of anti-IL-4 antibodies to mice with synchronously developing granulomas dramatically reduced granuloma size (40 to 50% suppression of area) during an 8-day study period, whereas antibodies to IFN had no effect on size. However, the latter treatment reduced giant cell formation. Our results indicate that granuloma development involves an orchestrated production of cytokines possibly resulting from sequential participation of different Th cell populations. Moreover, IL-4 is a pivotal cytokine in anamnestic cellular recruitment and subject to endogenous regulation.

Cells of the synovial microenvironment may recruit neutrophils (PMN) and lymphocytes into synovial fluid, as well as lymphocytes into the synovial tissues, of arthritic patients. We have investigated the production of the chemotactic cytokine IL-8 by using sera, synovial fluid, synovial tissue, and macrophages and fibroblasts isolated from synovial tissues from 75 arthritic patients. IL-8 levels were higher in synovial fluid from rheumatoid (RA) patients (mean +/- SE, 14.37 +/- 5.8 ng/ml), compared with synovial fluid from osteoarthritis patients (0.135 +/- 17 ng/ml) (p less than 0.05) or from patients with other arthritides (5.52 +/- 5.11 ng/ml). IL-8 from RA sera was 8.44 +/- 2.33 ng/ml, compared with nondetectable levels found in normal sera. IL-8 levels from RA sera and synovial fluid were strongly positively correlated (r = 0.96, p less than 0.05). Moreover, RA synovial fluid chemotactic activity for PMN in these fluids was inhibited 40 +/- 5% upon incubation with neutralizing polyclonal antibody to IL-8. Synovial tissue fibroblasts released only small amounts of constitutive IL-8 but could be induced to produce IL-8 by stimulation with either IL-1 beta, TNF-alpha, or LPS. In contrast, unlike normal PBMC or alveolar macrophages, macrophages isolated from RA synovial tissue constitutively expressed both IL-8 mRNA and antigenic IL-8. RA synovial macrophage IL-8 expression was not augmented by incubation with either LPS, TNF-alpha, or IL-1 beta. Immunohistochemical analysis of synovial tissue showed that a greater percentage of RA macrophages than osteoarthritis macrophages reacted with anti-IL-8. Whereas macrophages were the predominant cell for immunolocalization of IL-8, less than 5% of synovial tissue fibroblasts were positive for immunolocalized IL-8. These results suggest that macrophage-derived IL-8 may play an important role in the recruitment of PMN in synovial inflammation associated with RA.