The embodiments of the invention are multiple antibody immunoassay systems, and preferably immunohistochemical staining systems. In these systems the detection antibody system that detects the association of a targeting antibody (that binds to the target moiety to be detected) may also cross-react with endogenous immunoglobulins in the specimen in which the target moiety is to be detected, yielding an unreliable assay with high background levels. This problem has been overcome by a process that includes cross-linking a monovalent antibody to the endogenous antigenic determinants prior to exposure to the targeting antibody and detecting antibody system. The embodiments of the invention also include kits for use in these multiple antibody immunoassay and histochemical staining systems.