Su H, Spangrude G J, Caldwell H D
Laboratory of Intracellular Parasites, Rocky Mountain Laboratories, National Institutes of Health, Hamilton, Montana 59840.
Infect Immun. 1991 Oct;59(10):3811-4. doi: 10.1128/iai.59.10.3811-3814.1991.
The neutralizing activities of a murine immunoglobulin G3 (IgG3) monoclonal antibody specific for the major outer membrane protein of Chlamydia trachomatis and its monovalent Fab fragments were studied by using Syrian hamster kidney (HaK) cells and human epithelial (HeLa 229) cells. The intact IgG3 antibody was neutralizing for HaK cells but was nonneutralizing for HeLa cells. In contrast, monovalent Fab antibody fragments neutralized chlamydial infectivity for both HaK and HeLa cells. Immunofluorescence analysis of HeLa 229 cells with a panel of monoclonal antibodies specific to human Fc gamma receptors revealed the expression of cell surface Fc gamma RIII. We propose that Fc gamma RIII may obscure the chlamydia-neutralizing activity of certain IgG isotypes by facilitating the Fc gamma R-mediated entry of chlamydiae into HeLa 229 cells. These findings may help explain the inconsistencies that are commonly observed in results when HeLa 229 cells are used in chlamydia neutralization assays.
利用叙利亚仓鼠肾（HaK）细胞和人上皮（HeLa 229）细胞，研究了一种针对沙眼衣原体主要外膜蛋白的鼠免疫球蛋白G3（IgG3）单克隆抗体及其单价Fab片段的中和活性。完整的IgG3抗体对HaK细胞具有中和作用，但对HeLa细胞无中和作用。相比之下，单价Fab抗体片段对HaK细胞和HeLa细胞的衣原体感染性均具有中和作用。用一组针对人Fcγ受体的单克隆抗体对HeLa 229细胞进行免疫荧光分析，结果显示细胞表面存在FcγRIII的表达。我们推测，FcγRIII可能通过促进FcγR介导的衣原体进入HeLa 229细胞，从而掩盖某些IgG同种型的衣原体中和活性。这些发现可能有助于解释在使用HeLa 229细胞进行衣原体中和试验时，结果中常见的不一致现象。
