| Popis: |
A previous study has shown that guinea-pig splenic Tγ lymphocytes bearing receptors for guinea-pig Fcγ1 or Fcγ2 immunoglobulins delineate two distinct T-cell phenotypes (Ricardo, 1980). In this study, the proportion of splenic Tγ1 and Tγ2 lymphocytes were found to vary considerably among different guinea-pigs. Furthermore, the binding of homologous IgG1 soluble immune complexes to guinea-pig splenic Tγ1 cells led to the modulation of their Fcγ1-receptors, while the Fcγ2-receptors on guinea-pig splenic Tγ2 cells were not affected. The re-appearance of Fcγ1-receptors after in vitro modulation was detected by inhibiting their EA-rosetting capabilities with homologous aggregated purified IgG1. Following modulation, re-appearance of EA-rosetting by Tγ1 cells was first detected in 48-hr cultures and by 72 hr their numbers had plateaued to half that present in T-lymphocyte preparations not exposed to immune complexes. Thus, the re-appearance of Tγ1 cells was slow and some Tγ1 cells may have irreversibly lost their Fc-receptors subsequent to binding IgG1 immune complexes. Conversely, when Tγ2 cells were exposed to homologous IgG2-soluble immune complexes only Fcγ2 receptors were modulated. The pattern of their re-appearance followed that of the modulated Fcγ1-receptors. These results demonstrated that Fc-receptors on guinea-pig splenic Tγ lymphocytes display isotype specificity for homologous IgG1 and IgG2 molecules and that these receptors can be modulated independently. The presence of isotype-specific Fc-receptors on guinea-pig Tγ lymphocytes could be an important surface determinant involved in the regulation of immune reactions mediated by homologous IgG1 and/or IgG2 antibodies. |
