| Abstract: | The objective of this study was to elucidate the cellular mechanism of IgE nonresponse to the Cryptomeria japonica (Japanese cedar) pollen antigen (CPAg), which was shown in our previous study to be HLA-linked (1). We established an assay system for the measurement of small amounts of anti-CPAg IgE antibody, both in an antigen-specific and isotype-specific manner, and a culture system to induce antigen-driven IgE antibody synthesis in vitro. By using these methods, we clarified that the function of the HLA-DR molecule in the CPAg-driven IgE response is similar to that of I-A or I-E molecule in mice, namely the product of immune response genes (Ir-genes), because anti-HLA-DR monoclonal antibody blocked the response, and the interaction between monocyte and monocyte-depleted peripheral blood lymphocytes (PBL) to respond to CPAg was restricted by HLA-DR. Furthermore, PBL from nonresponders revealed a specific IgE response to CPAg when the Leu-2+3- T cell fraction was depleted, thereby suggesting that even nonresponders have Leu-2-3+ T cell and B cell clones specific for CPAg, and they apparently show no response due to the presence of CPAg-specific Leu-2+3- suppressor T cells. This suppressor T cell fraction abolished the IgE response of the autologous B + monocyte + Leu-2-3+ T cell in a CPAg-specific manner. The current cellular analysis together with our previous genetic analysis strongly suggest that the HLA-linked IgE nonresponse to CPAg is mediated by CPAg-specific suppressor T cells. The HLA-linked gene controlling the nonresponsiveness to CPAg is thus designated as the immune suppression gene for CPAg (Is-CPAg). Mapping of Is-CPAg within HLA-DQ subregion is discussed. |
