Kehry M R, Yamashita L C
Department of Immunology, DNAX Research Institute of Molecular and Cellular Biology, Inc., Palo Alto, CA 94304-1104.
Proc Natl Acad Sci U S A. 1989 Oct;86(19):7556-60. doi: 10.1073/pnas.86.19.7556.
B-cell surface immunoglobulin very efficiently focuses specific protein antigens for presentation to T cells. We have demonstrated a similar role in antigen focusing for the low-affinity Fc epsilon receptor (Fc epsilon RII) on mouse B lymphocytes. B cells treated with an IgE monoclonal antibody to 2,4,6-trinitrophenyl (TNP) (IgE-B cells) were 100-fold more effective than were untreated B cells in presenting low concentrations of TNP-antigen to T cells. Blocking the binding of IgE to Fc epsilon RII on IgE-B cells with a monoclonal antibody to Fc epsilon RII completely eliminated this increased effectiveness. Preformed complexes of IgE anti-TNP and TNP-antigen were more effectively presented (approximately 100-fold) than TNP-antigen in the presence of nonspecific IgE. In contrast, complexes of IgG1 anti-TNP and TNP-antigen, capable of binding to Fc gamma receptors on B cells, were presented less effectively than TNP-antigen in the presence of nonspecific IgG1. Antigens focused by means of Fc epsilon RII or by means of B-cell surface immunoglobulin receptors were presented at comparably low concentrations. For several reasons, Fc epsilon RII on B lymphocytes seems to be particularly effective in efficiently focusing IgE-antigen complexes.
B细胞表面免疫球蛋白能非常有效地聚集特定蛋白质抗原，以呈递给T细胞。我们已经证明，小鼠B淋巴细胞上的低亲和力Fcε受体（FcεRII）在抗原聚集中也发挥类似作用。用针对2,4,6-三硝基苯（TNP）的IgE单克隆抗体处理的B细胞（IgE-B细胞），在向T细胞呈递低浓度TNP抗原时，其效率比未处理的B细胞高100倍。用针对FcεRII的单克隆抗体阻断IgE与IgE-B细胞上FcεRII的结合，可完全消除这种增强的效率。预先形成的IgE抗TNP和TNP抗原复合物，在存在非特异性IgE的情况下，比TNP抗原更有效地被呈递（约100倍）。相比之下，能够结合B细胞上Fcγ受体的IgG1抗TNP和TNP抗原复合物，在存在非特异性IgG1的情况下，比TNP抗原的呈递效率更低。通过FcεRII或通过B细胞表面免疫球蛋白受体聚集的抗原，在相当低的浓度下就能被呈递。出于几个原因，B淋巴细胞上的FcεRII似乎在有效聚集IgE-抗原复合物方面特别有效。
