ABSTRACT
Zupanska et al. (61) showed that to obtain a given number of rosettes, only about one-quarter of the number of molecules was required for lgG3 compared with IgGl. Also, the threshold number of IgG3 molecules bound per RBC required for adherence to monocytes was found to be lower (180--460) from the required numbers of IgG 1 (1180--4300). They also found that RBCs sensitized in vitro with IgG3 anti-D but not sensitized with IgG 1 anti-D antibodies showed adherence to monocytes in vitro when the direct antiglobulin test (DAT) on those RBCs was negative (61). The foregoing results obtained with polyclonal antibodies have been confirmed using different human monoclonal IgG 1 and IgG 3 anti-D antibodies ( 45). The preponderance of lgG3 activity was also shown in other cellular assays-in the MMA, CLT, and ADCC (M) using polyclonal as well as monoclonal anti-D antibodies (62, 92-98). Wiener et al. (92) have found a more pronounced difference in binding oflgG3 and IgG 1 monoclonal anti-D antibodies (100 and 10000 molecules per RBC, respectively) when using cultured monocytes stimulated with interferon gamma. Further investigations have, in addition, shown that the interaction with RBCs sensitized with lgG3 anti-D was much more rapid in the MMA than with cells sensitized with lgG 1 antibodies. Maximum interaction was achieved within 30 mins and 2 hrs, respectively (99). This difference also was reflected in the kinetics of CL response to lgG 1-or lgG3-sensitized RBCs (41).
