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Chemokine receptors transduce signals important for the function and trafficking of leukocytes. Recently, it has been shown that CC chemokine receptor (CCR)8 is selectively expressed by Th2 subsets, but its functional relevance is unclear. To address the biological role of CCR8, we generated CCR8 deficient (-/-) mice. Here we report defective T helper type 2 (Th2) immune responses in vivo in CCR8(-/)- mice in models of Schistosoma mansoni soluble egg antigen (SEA)-induced granuloma formation as well as ovalbumin (OVA)- and cockroach antigen (CRA)-induced allergic airway inflammation. In these mice, the response to SEA, OVA, and CRA showed impaired Th2 cytokine production that was associated with aberrant type 2 inflammation displaying a 50 to 80% reduction in eosinophils. In contrast, a prototypical Th1 immune response, elicited by Mycobacteria bovis purified protein derivative (PPD) was unaffected by CCR8 deficiency. Mechanistic analyses indicated that Th2 cells developed normally and that the reduction in eosinophil recruitment was likely due to systemic reduction in interleukin 5. These results indicate an important role for CCR8 in Th2 functional responses in vivo.

Human herpesvirus 8 (HHV8, also known as Kaposi's sarcoma [KS]-associated herpesvirus) has been implicated as an etiologic agent for KS, an angiogenic tumor composed of endothelial, inflammatory, and spindle cells. Here, we report that transgenic mice expressing the HHV8-encoded chemokine receptor (viral G protein-coupled receptor) within hematopoietic cells develop angioproliferative lesions in multiple organs that morphologically resemble KS lesions. These lesions are characterized by a spectrum of changes ranging from erythematous maculae to vascular tumors, by the presence of spindle and inflammatory cells, and by expression of vGPCR, CD34, and vascular endothelial growth factor. We conclude that vGPCR contributes to the development of the angioproliferative lesions observed in these mice and suggest that this chemokine receptor may play a role in the pathogenesis of KS in humans.

Macrophage inflammatory protein 1 alpha (MIP-1 alpha) is a 6-8-kD, lipopolysaccharide-inducible monocyte and neutrophil chemotactic protein that may be important in acute and chronic inflammation. The present study determined the sequential production, source, and in vivo contribution of murine MIP-1 alpha in synchronized Schistosoma mansoni egg pulmonary granuloma formation. Granulomas were examined under conditions of primary, secondary vigorous, and secondary immunomodulated immunity. Secreted MIP-1 alpha was measured in 24-h supernatants from intact granulomas (700/ml) cultured with or without soluble egg antigen (SEA). Primary granulomas isolated from naive mice over a 16-d period showed low spontaneous MIP-1 alpha production (< 1 ng/ml). However, when primary granulomas were challenged with SEA, significant MIP-1 alpha production was observed beginning at day 4 and peaking at day 16. Intact vigorous (isolated from 8-wk-infected mice) and modulated (isolated from 20-wk-infected mice) secondary pulmonary granulomas demonstrated comparable spontaneous MIP-1 alpha production. Addition of SEA to vigorous stage granulomas augmented expression of MIP-1 alpha at all time points, whereas stimulated modulated stage granulomas did not increase production. The latter observation is likely related to endogenous immunoregulatory mechanisms reported for modulated stage animals. Immunohistochemical localization of MIP-1 alpha in granuloma sections and cytocentrifuge preparations from vigorous lesions localized MIP-1 alpha production to macrophages within granulomas. Treatment of mice with rabbit anti-mouse MIP-1 alpha antibodies significantly decreased 8-d primary granuloma formation (> 40%) when compared with control mice. Anti-MIP-1 alpha sera also decreased vigorous (> 20%), but not modulated granuloma formation. These findings demonstrate that MIP-1 alpha contributes to cellular recruitment during schistosome egg granuloma formation.

Host granulomatous inflammation in murine schistosomiasis mansoni is a T cell-mediated immune response, which, at the chronic stage of the disease, undergoes T suppressor lymphocyte-dependent modulation. In the present study this phenomenon was further analyzed in vitro. Spleen cells of mice undergoing modulation (20 wk of infection) when mixed with spleen cells of animals exhibiting vigorous granulomatous responses (8 wk of infection) abrogated in vitro migration inhibition factor (MIF) production by the latter. Characterization of the delayed-type hypersensitivity T lymphocytes involved in lymphokine production showed that they belonged to the Lyt-1+ subset and did not express I region-encoded antigens. In contrast, T lymphocytes involved in the suppression of MIF activity belonged to the Lyt-2+ subpopulation of cells, which expressed I-J- and I-C-subregion determinants. These results suggest that the modulation of the granulomatous hypersensitivity response in mice is the result of T-T cell interaction with subsequent regulation of inflammatory lymphokine production.

In the present study, we extended the analysis of the regulation of inflammatory lymphokine production in mice with schistosomiasis mansoni. Splenic lymphocytes of chronically infected mice were briefly pulsed in vitro by soluble egg antigens, washed, and then cultured overnight. The supernatant culture fluid added to cultures of splenic cells of acutely infected or peritoneal lymphocytes of antigen-sensitized mice inhibited the production of migration inhibition factor (MIF). Elaboration of MIF suppressor factor (MIF-SF) required the Lyt-1-,2+,3+ subset of T lymphocytes. MIF-SF acted only on egg antigen-primed cells and required H-2 compatibility with the target cell for its suppressive effect. Further analysis with recombinant strains revealed that the factor interacted with I-AB or I-C subregion-compatible target cells. Experiments using immunoadsorbent columns with bound anti-I subregion alloantisera indicated that MIF-SF contained I-C subregion-encoded determinants. Extrapolation of this in vitro model to in vivo conditions would indicate that the granulomatous response is modulated by I region-derived suppressor factor(s) that regulate lymphokine production by TDH effector cells.