AppDomain and Remoting

Hi, I'm currently building my own plug-in library. I don't want to use existing extensibility libraries due to several reasons.
Anyway, this is how I do it:

I create new appdomains to hold my plug-ins to easily unload them:

Code:

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AppDomain appDomain = AppDomain.CreateDomain("newdomain", AppDomain.CurrentDomain.Evidence, setup);

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Then I inject my library to load the necessary assemblies and instantiate it:

Code:

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Loader ldr = (Loader)sandboxedDomain.CreateInstanceFromAndUnwrap(typeof(Loader).Assembly.Location, typeof(Loader).FullName);

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And from there I can load my real plug-in that implements MarshalByRefObj and call its members.
But from the application domain of my plug-in; how can I get some of the objects from the host's AppDomain?
I'm avoiding the usage of TCP and I want to directly connect through the AppDomain.

Thanks for response.