I worked in the 80s for Cetus Corporation producing monoclonal antibodies. We had a rat monoclonal production effort and as I recall, we obtained IR983F directly from Louvain University when Herve Bazin was head of Experimental immunology. Bazin is no longer with the University but that would probably be the best place to go. As for Cetus, it was bought by Chiron, which in turn has been bought by Novartis. I can't imagine that would be a useful avenue of inquiry since that work was done over thirty years ago. Good luck.