Several murine monoclonal antibodies have been used as targeting agents for radioimmunoscintigrapy and radioimmunotherapy. However, there is a possibility that these antibodies bind to normal blood cells. And these bindings can cause adverse or
favourable results in the radioimmunoscintigrapy and immunotherapy. In this investigation, we tried to evaluate the bindings between normal blood cells and commonly used murine monoclonal antibodies. Such as IgG2a. We used B-72.3. COL-1 as murine
IgG1
antibodies and 9.2.27, 2-135, T-101 as murine IgG2a antibodies.
1) Neither monoclonal antibodies IgG2a bound to normal red blood cells.
2) Monoclonal antibody IgG1 won't bind to normal white blood cells. But IgG2a antibodies showed specific bindings with white blood cells.
3) Monoclonal antibody IgG2a didn't bind to T-lymphocytes. However, it bound to monocytes specifically which was confirmed by FACS analysis.
4) Bindings of 125I-9.2.27(IgG2a) to monocytes were inhibited by addition of other IgG2a antibodies or Fc fragment. This binding was not inhibited by adding F(ab')2 fragments of IgG2a. These findings suggested that binding of IgG2a to monocyte
was
related with Fc receptor of monocytes.
5) From the Scatchard analysis, the association constant(Ka) and receptor number of monocytes were derived as 1.2~1.5×10E9/mole, and 2.2~3.1×10E4/cell, respectively.
6) After binding of 125I-9.2.27 to monocytes, these cells were cultured until 24 hours. Cell bound 125I-9.2.27 gradually disappeared from monocytes. And progressive accumulation of radioactivity in the culture supernatants occurred throughout
the
culture period.
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