Analysis of inducible costimulatory molecule participation during the induction and elicitation of granulomatous responses to mycobacterial and schistosomal antigens.

The contribution of inducible costimulatory molecule (ICOS) to Th1 and Th2 cell-mediated immune responses was examined in well-defined pathogen antigen-elicited models of cell-mediated granuloma formation. Th1 and Th2 granulomas were respectively induced by intravenous challenge of CBA/J mice with Mycobacteria bovis purified protein derivative (PPD) or Schistosoma mansoni egg (SEA) antigen-coated beads. Effects of anti-ICOS blocking antibody on granulomas and lymphoid responses were assessed during elicitation and sensitization. Anti-ICOS treatment during the elicitation abrogated Th1- but not Th2-cell-mediated granuloma formation. Treatment during sensitization augmented SEA-bead granulomas and Th2 cytokines in lymphoid tissue. Anti-ICOS reduced the primary inflammatory response to PPD- but not to SEA-beads, despite comparable induction of ICOS-ligand and ICOS+ T cells. Treatment did not prevent early development of IFNgamma producing cells. Thus, post-activation effector Th1 activity was subject to ICOS blockade and chronic treatment caused diversion to Th2 dominance likely by eroding Th1 effector function or survival.

The innate pulmonary granuloma: characterization and demonstration of dendritic cell recruitment and function.

Granulomas are innate sequestration responses that can be modified by superimposed acquired immune mechanisms. The present study examined the innate stage of pulmonary granuloma responses to bead-immobilized Th1- and Th2-inducing pathogen antigens (Ags), Mycobacteria bovis purified protein derivative (PPD) and Schistosoma mansoni soluble egg Ags (SEA). Compared to a nonpathogen Ag, PPD and SEA bead elicited larger lesions with the former showing accelerated inflammation. Temporal analyses of cytokine and chemokine transcripts showed all Ag beads induced tumor necrosis factor-alpha mRNA but indicated biased interleukin (IL)-1, IL-6, and IL-12 expression with PPD challenge. All beads elicited comparable levels of CXCL9, CXL10, CCL2, CCL17, and CCL22 mRNA, but PPD beads caused biased CXCL2 CXCL5, CCL3, and CCL4 expression whereas both pathogen Ags induced CCL7. Immunohistochemical, electron microscopic, and flow cytometric analyses showed that Ag beads mobilized CD11c+ dendritic cells (DCs) of comparable maturation. Transfer of DCs from PPD Ag-challenged lungs conferred a Th1 anamnestic cytokine response in recipients. Surprisingly, transfer of DCs from the helminth SEA-challenged lungs did not confer the expected Th2 response, but instead rendered recipients incapable of Ag-elicited IL-4 production. These results provide in vivo evidence that lung DCs recruited under inflammatory conditions favor Th1 responses and alternative mechanisms are required for Th2 commitment.

Cytokine-chemokine networks in experimental mycobacterial and schistosomal pulmonary granuloma formation.

Type-1 and type-2 lung granulomas, respectively, elicited by bead immobilized Mycobacteria bovis and Schistosoma mansoni egg antigens (Ags) display different patterns of chemokine expression. This study tested the hypothesis that chemokine expression patterns were related to upstream cytokine signaling. Using quantitative transcript analysis, we defined expression profiles for 16 chemokines and then examined the in vivo effects of neutralizing antibodies against interferon-gamma (IFN-gamma), interleukin (IL)-4, IL-10, IL-12, and IL-13. Transcripts for CXCL2, -5, -9, -10, and -11 and the CCL chemokine, CCL3, and lymphotactin (XCL1), were largely enhanced by Th1-related cytokines, IFN-gamma or IL-12. Transcripts for CCL11, CCL22, CCL17, and CCL1 were enhanced largely by Th2-related cytokines, IL-4, IL-10, or IL-13. Transcripts for CCL4, CCL2, CCL8, CCL7, and CCL12 were potentially induced by either Th1- or Th2-related cytokines, although some of these showed biased expression. IFN-gamma and IL-4 enhanced the greatest complement of transcripts, and their neutralization had the greatest anti-inflammatory effect on type-1 and type-2 granulomas, respectively. Th1/Th2 cross-regulation was evident because endogenous Th2 cytokines inhibited type-1, whereas Th1 cytokines inhibited type-2 biased chemokines. These findings reveal a complex cytokine-chemokine regulatory network that dictates profiles of local chemokine expression during T cell-mediated granuloma formation.

Population analysis of CD4+ T cell chemokine receptor transcript expression during in vivo type-1 (mycobacterial) and type-2 (schistosomal) immune responses.

Chemokine receptor transcripts were defined among CD4+ T cells in lymph nodes of mice with type-1 and type-2 inflammation, respectively, elicited by mycobacterial and schistosomal Ag. CXCR3 and CCR6 transcripts were biased to type-1, and CCR4 transcripts increased in type-1 and type-2 populations. CCR3 and CCR5 signals were too weak to establish differences. CCR8 transcripts were not increased among unstimulated populations. Compared to naïve, type-1 and type-2 populations had reduced CCR7 and enhanced CXCR5 transcripts, consistent with a shift to memory cells. Subset depletion revealed that transcript expression was induced among CD44+ memory T cells. Surprisingly, CCR3 transcripts were enriched among CD44lo fractions. Ag stimulation augmented CXCR3, CCR4, and CCR8 but down-regulated CCR6 and CXCR5. CCR4 showed association with IFN-gamma- and IL-4-producing cells, but other receptor transcripts were expressed among IFN-gamma/IL-4 negative memory T cells. These studies provide several novel findings regarding Th cell chemokine receptor expression in vivo.

Differential effects of ageing on cytokine and chemokine responses during type-1 (mycobacterial) and type-2 (schistosomal) pulmonary granulomatous inflammation in mice.

Cytokine and chemokine responses during anamnestic type-1 and type-2 lung granuloma formation were evaluated in mice at 6,12,18 and 24-months of age. Lesions were induced by embolizing Sepharose beads coupled to Mycobacterium bovis purified protein derivative or soluble Schistosoma mansoni egg antigens. Type-1 inflammation was reduced by 18 months, whereas type-2 granulomas not until 24 months of age. In type-1 draining lymph nodes cultures, interferon-gamma (IFNgamma) declined to a nadir by 18, and then partly recovered at 24 months. In contrast, IL-4 was not significantly impaired in type-2 cultures until 24 months. Type-1 and 2 node cultures also displayed decreased IL-13, but paradoxically enhanced IL-5 production at 24 months. Chemokine transcripts in granulomatous lungs displayed age-related alterations. In the type-1 response, CXCL9 (monokine-induced by IFNgamma) declined with age then partly recovered at 24 months parallelling lymph node IFNgamma levels. Transcripts for MIP-2/CXCL2, IP-10/CXCL10, MCP-1/CCL2, and MCP-5/CCL12 increased at 24 months. In the type-2 response MCP-1/CCL2, MCP-3/CCL7, MCP-5/CCL12 and TARC/CCL17 collapsed at 24 months paralleling local IL-4 transcript levels, yet some chemokine transcripts such as KC/CXCL1 and eotaxin/CCL11 were unaffected. These findings suggest that cytokine and chemokine responses degrade differentially with age shifting Th1/Th2 crossregulatory pressures and local expression of chemokines.