Immunofluorescence study of thymuses of mice given Friend leukemia virus: conventional vs monoclonal antibodies.

In the course of a study of the early effects of Friend Leukemia Virus (FLV) infection in thymus structure and function, evidence of early localization of infectious FLV in the thymic type I and type II epithelio-reticular cells of susceptible mice was obtained. Such evidence was based upon bio-assay, ultrastructural and immunofluorescence observations. As for the latter, conventional monospecific sera against FLV p30 and gp70 antigens as well as two distinct monoclonal antibodies recognizing FLV gp70 epitopes were employed. Both monoclonal antibodies stained with a granular pattern the cytoplasm of type I and II epithelio-reticular cells from susceptible mice injected with live FLV. On the contrary, conventional monospecific sera diffusely stained the cytoplasm of all epithelio-reticular cells of the thymus, independently of mice inoculation with and susceptibility to virus, possibly recognizing tissue-associated normal mouse antigens and/or cross-reacting antigens of other ecotropic viruses.