The generation of knockout mice demonstrated that noncytotoxic CD4+, but not cytotoxic CD8+, T cells were essential for the rejection of skin or organ allografts. Earlier we reported that allograft‐induced macrophages (AIM) in mice lysed allografts with H‐2 haplotype specificity, implying screening of grafts by AIM. Here, we isolated a cDNA clone encoding a novel receptor on AIM (H‐2Db) for an allogeneic major histocompatibility complex (MHC) class I molecule, H‐2Dd, by using H‐2Dd tetramer and a monoclonal antibody (mAb; R15) specific for AIM. The cDNA (1,181‐bp) encoded a 342‐amino acid polypeptide with a calculated molecular mass of 45 kDa and was found to be expressed on AIM, but not on resident macrophages or other cells, infiltrating into the rejection site. HEK293T cells transfected with this cDNA reacted with R15 mAb and H‐2Dd, but not H‐2Ld, H‐2Kd, H‐2Db, H‐2Kb, H‐2Dk, or H‐2Kk, molecules; and the H‐2Dd binding was suppressed by the addition of R15 or anti‐H‐2Dd mAb. AIM yielded a specific saturation isotherm in the presence of increasing concentrations of H‐2Dd, but not H‐2Db or H‐2Dk, molecules. The dissociation constant of AIM toward H‐2Dd tetramers was 1.9×10–9 M; and the binding was completely inhibited by the addition of R15 or anti‐H‐2Dd mAb. These results reveal that a novel receptor for an allogeneic H‐2Dd molecule was induced on effector macrophages responsible for allograft (H‐2d) rejection in H‐2b mice.

No abstract

To explore which cytokine or cell is essential for the production of antibodies (Abs) of the IgE class in allergic diseases, we injected cedar pollen into wild-type, interferon-gamma(-/-) (IFN-gamma(/)), or interleukin-4(-/-) (IL-4(-/-)) BALB/c mice through four (i.n., i.p., s.c., and i.v.) different routes without adjuvant. Wild-type or IFN-gamma(-/-), but not IL-4(-/-), mice sensitized once or twice showed a significant increase in total IgE Ab in their serum, revealing the essential role of IL-4 in the production of total IgE Ab. We separated peripheral blood mononuclear cells (PBMCs) from untreated or sensitized mice into monocyte-rich, lymphocyte-rich, and granulocyterich populations by Percoll density-gradient centrifugation or into specific antigen cells by flow cytometry, cultured the cells in various combinations, and examined the levels of cytokines and IgE Ab released into the medium. The PBMCs from mice sensitized s.c. once, but not those from untreated animals, produced significant amounts of IL-4 and total IgE Ab, whereas the lymphocyte-rich population alone did not. Unexpectedly, IL-4 and IgE Ab production was restored by the addition of Mac-1(+) cells in the monocyte-rich fraction to the lymphocyte-rich fraction. These results indicate the essential role of monocytes in the production of IL-4 and total IgE Ab by lymphocytes during the initial stage of sensitization.

No abstract

The production of specific IgE antibodies directed toward cedar pollen correlates well with the onset of allergic rhinitis; but the mechanisms of allergen recognition as nonself and Ig class switch to IgE by the immune system are still not fully understood. In the present study, we injected cedar pollen into mice through 4 different routes (intranasal (i.n.), intraperitoneal (i.p.), intravenous (i.v.), and subcutaneous (s.c.)) without adjuvant 1 to 3 times, and determined time‐dependent changes in the total and specific serum IgE levels compared with those in the serum levels of other isotype Igs. After an i.p. or i.n. injection of allergen into the mice, they produced a 1.5‐ to 1.7‐fold increase in total IgE, but none in IgG, IgM, or IgA antibodies in their serum, whereas an i.v. or s.c. injection of allergen was inactive as an inducer of total IgE antibodies. Upon a 2nd (s.c.) injection of the allergen into the i.p. or i.n. sensitized mice, a large amount of allergen‐specific IgE antibodies was found in the serum. In the case of i.v. or s.c. sensitized mice, however, they produced total, but not specific, IgE antibodies; and a 3rd (s.c.) injection of the allergen resulted in a large amount of specific IgE antibodies in the serum. These results imply that resident cells at the i.p. or i.n. injection site may play a crucial role in the efficient production of total and specific IgE antibodies toward the allergen.