IL-13-mediated worm expulsion is B7 independent and IFN-gamma sensitive

B7 costimulation is a required component of many type 2 immune responses, including allergy and protective immunity to many nematode parasites. This response includes elevations in Th2 cytokines and associated effector functions including elevations in serum IgG1 and IgE and parasite expulsion. In studies of mice infected with Trichuris muris, blocking B7 ligand interactions inhibited protective immunity, suppressed IL-4 production, and enhanced IFN-gamma production, but unexpectedly did not inhibit production of the Th2 cytokine, IL-13. Blocking both IFN-gamma and B7 restored protective immunity, which was IL-13 dependent, but did not restore IL-4 or associated IgE responses. Although IL-13 was required for worm expulsion in mice in which both IFN-gamma and B7 were blocked, IL-4 could mediate expulsion in the absence of both IL-13 and IFN-gamma. These studies demonstrate that 1) B7 costimulation is required to induce IL-4, but not IL-13 responses; 2) IL-13 is elevated in association with the IFN-gamma response that occurs following inhibition of B7 interactions, but can only mediate IL-4-independent protection when IFN-gamma is also inhibited; and 3) increased IL-13 production, in the absence of increased IL-4 production, is not associated with an IgE response, even in the absence of IFN-gamma.

B7-2 is required for the progression but not the initiation of the type 2 immune response to a gastrointestinal nematode parasite

T cells require CD28/CTLA-4 costimulatory molecule interactions in addition to Ag-specific signals through the TCR for in vivo effector Th cell function. Some studies have suggested that the ligands for these costimulatory molecules may differentially influence effector T cell function with B7-2 favoring a type 2 response and B7-1 favoring a type 1 response, while other studies have suggested that these molecules may be redundant. The recent development of B7-2-deficient mice permits the direct analysis of the requirement of B7-2 during a type 2 immune response to an infectious pathogen. We have examined, in B7-2-deficient mice, effector Th cell function and the associated type 2 immune response following infection with Heligmosomoides polygyrus, a natural murine parasitic nematode. Elevations in cytokine gene expression and protein secretion were pronounced and comparable in inoculated B7-2-/- and B7-2+/+ mice at day 8 after H. polygyrus inoculation. However, by day 14 after infection, increases in T cell cytokine expression were markedly inhibited in H. polygyrus-inoculated B7-2-/- mice. Furthermore, elevations in serum IgE and germinal center formation were inhibited at later stages of the immune response, while elevations in serum IgG1 persisted. These findings suggest that certain T-dependent components vary in their B7-2-dependency during the type 2 immune response. They further demonstrate that B7-2 interactions are not necessary for the initiation of the type 2 immune response, but are instead required for its progression after the development of effector T cells.

B7-2 Is Required for the Progression But Not the Initiation of the Type 2 Immune Response to a Gastrointestinal Nematode Parasite

T cells require CD28/CTLA-4 costimulatory molecule interactions in addition to Ag-specific signals through the TCR for in vivo effector Th cell function. Some studies have suggested that the ligands for these costimulatory molecules may differentially influence effector T cell function with B7-2 favoring a type 2 response and B7-1 favoring a type 1 response, while other studies have suggested that these molecules may be redundant. The recent development of B7-2-deficient mice permits the direct analysis of the requirement of B7-2 during a type 2 immune response to an infectious pathogen. We have examined, in B7-2-deficient mice, effector Th cell function and the associated type 2 immune response following infection with Heligmosomoides polygyrus, a natural murine parasitic nematode. Elevations in cytokine gene expression and protein secretion were pronounced and comparable in inoculated B7-2−/− and B7-2+/+ mice at day 8 after H. polygyrus inoculation. However, by day 14 after infection, increases in T cell cytokine expression were markedly inhibited in H. polygyrus-inoculated B7-2−/− mice. Furthermore, elevations in serum IgE and germinal center formation were inhibited at later stages of the immune response, while elevations in serum IgG1 persisted. These findings suggest that certain T-dependent components vary in their B7-2-dependency during the type 2 immune response. They further demonstrate that B7-2 interactions are not necessary for the initiation of the type 2 immune response, but are instead required for its progression after the development of effector T cells.