No abstract

Asthma is characterized by the presence of an inflammatory cell infiltrate in the bronchial mucosa consisting of activated mast cells, eosinophils, and T cells. Several cytokines are considered to play a pivotal role in this response, particularly interleukin (IL)-4, IL-5, IL-6, and tumor necrosis factor-alpha (TNF-alpha). In this study, we have used immunohistochemistry applied to thin glycol methacrylate sections of bronchial mucosal biopsies to define the cellular provenance of these cytokines in normal and asthmatic airways. Both the asthmatic and normal mucosa contained numerous cells staining positively for all four cytokines, with the majority identified as mast cells by their tryptase content. Eosinophils also accounted for some IL-5 immunostaining in the asthmatic biopsies. By using two monoclonal antibodies directed to different epitopes of IL-4, we provide tentative evidence for enhanced IL-4 secretion in asthma. Similarly, a sevenfold increase in the number of mast cells staining for TNF-alpha in the asthmatic biopsies suggests that this cytokine is also up-regulated in this disease. These findings clearly identify human mast cells as a source of IL-4, IL-5, IL-6, and TNF-alpha and add to the view that, along with T cells, mast cells may play an important role in initiating and maintaining the inflammatory response in asthma.

SummaryRecent attention has focused on the T helper type 2 (Th2) lymphocyte as a source of interleukin 4 (IL 4) in allergic disease . However, Th2 cells themselves require a pulse of IL-4 to initiate this synthesis. Here we provide immunohistochemical evidence of IL-4 localization to human mast cells of the skin and respiratory tract, and demonstrate that immunoglobulin E-dependent stimulation of purified human lung mast cells leads to the rapid release of IL-4 into the extracellular environment . We propose that mast cell activation in an allergic response provides a rapid and local pulse of IL-4 into the local environment essential for the triggering of T lymphocytes into sustained IL-4 production and to initiate inflammatory cell accumulation and activation.

SummaryAn increased ratio of T helper type 2 (Th2)-vs Thl-like calls contributes to the immune dysregulation in allergic disease situations and in many chronic infections, including AIDS. Th2-type immune responses are characterized by Th cells that produce increased levels ofinterleukin-4 (IL-4) and decreased levels of interferon 3/(IFN-7). The induction of either a Thl-or a Th2-1ike phenotype may be critically controlled by the antigen-presenting ceUs and their cytokines, e.g., IFN-ce. In this study we have determined the frequencies of potential IL-4-and/or IFN-7-producing T cells in the peripheral blood of randomly selected healthy individuals, and analyzed whether IFN-ce controls IL-4 and/or IFN-7 production. Purified CD4 § or CD8 + T cells were stimulated for 24 h via the T cell receptor/CD3 complex in the presence or absence of IFN-cx, and single IL-4-and IFN-7-secreting cells were detected in enzyme-linked immunospot assays. In the absence of IFN-c~, CD4 cells produced IFN-7 at frequencies of 1:50-300, and produced IL-4 at frequencies of 1:110-<1:100,000. Addition of IFN-ol during the activation of CD4 cells increased the levels of IFN-7 mRNA. As a consequence, the numbers of IFN-7-producing CD4 cells and the amounts of secreted IFN-7 increased 10-fold. In contrast, IFN-c~ did not increase the frequency of IL-4-secreting CD4 cells. In the absence of IFN-o~, addition of exogenous IL-4 to cultures of CD4 cells suppressed IFN-7 secretion by 70%. However, in the presence of IFN-ce, IL-4 did not display any suppressive effect. Compared with CD4 cells, CD8 cells produced IFN-7 more frequently (1:5-10) but IL-4 less frequently (1:5,300 to <1:100,000). IFN-c~ did not display any effect on the frequency of either IFN-7 or IL-4 production by CD8 cells. Taken together the resuhs indicate that IFN-cx increases the frequency of IFN-7-secreting CD4 Th cells and antagonizes the suppressive effect of IL-4 on IFN-'y production. As a consequence, IFN-oc may favor the induction and maintenance of Thl-like cells and thereby counteract Th2-driven allergic immune responses. I FN-c~ has a wide range of immunomodulatory activities(1, 2). The cytokine has been used successfully for the treatment of viral infections (3-8), including AIDS (7, 8), and also displays beneficial effects in several tumor-associated diseases (9-12), and in allergic disorders (13,14). Despite the broad indication range for IFN-o~, the detailed mechanism of IFN-ol action in vivo as well as its target ceils have not been well defined. It has been found that IFN-c~ modulates the immunoglobulin isotype selection process, since it suppresses IgE production in an isotype-specific fashion in vitro (15) as well as in vivo (13,16,17). A direct effect of IFN-o~ on B calls is unlikely, since IFN-ce does not inhibit IgE switching of human B calls upon physical interaction with preactivated helper calls in the absence of IFN-7 and in the presence of exogenously added IL-2 and IL-4 (18). It is tempting to speculate that IFN-c~ suppresses IgE production by modulating ly...

Aerosol antigen challenge of ovalbumin-sensitized mice induced an eosinophilic airway inflammation that was dependent on interleukin (IL)-5 and CD4+, but not CD8+, T lymphocytes. The involvement of the Th2 phenotype of CD4+ T cells was supported by demonstrating that FACS-sorted purified lung T cells from sensitized, but not control, mice produced IL-4, IL-5, and IL-10 after activation of the CD3/TCR complex. To determine the role of IL-4 in this process, we used mice in which the gene for IL-4 was deleted by homologous recombination. Antigen challenge of IL-4 gene-targeted mice resulted in a marked attenuation of eosinophilic inflammation and IL-5 secretion. To more fully understand the time when IL-4 was involved, we administered a neutralizing anti-IL-4 antibody (11B11) either immediately before antigen challenge or during immunization. Inhibition of IL-4 before antigen challenge had little effect on antigen-induced eosinophil infiltration. However, when 11B11 was administered during immunization, there was a marked reduction in eosinophil infiltration. Cross-linking of the CD3/TCR complex of FACS-sorted lung T cells revealed that only when anti-IL-4 was administered during immunization was there an inhibition of T cell-derived IL-5 and IgE production. These results suggest that IL-4 is central both to the induction of a local Th2 response and to the development of eosinophilic inflammation of the lung. Moreover, we suggest a sequential involvement of IL-4 and IL-5, with IL-4 committing naive T cells to a Th2 phenotype which upon activation by aerosol provocation secrete IL-5, resulting in eosinophil accumulation.