Identification of rabbit and mouse β-glucuronidases in human fibroblasts following direct interaction with lymphocytes

Human fibroblasts totally deficient in β-glucuronidase acquired high levels of enzyme activity when co-cultured with mouse or rabbit lymphocytes. Direct cell-to-cell contact was obligatory for this process. The enzyme acquired by the fibroblasts was shown to be identical to β-glucuronidase from donor lymphocytes by its position of elution from DEAE-cellulose, thermal stability, mobility on polyacrylamide gels and by its antigenic determinants. The enzyme extracted from deficient fibroblasts after co-culture with lymphocytes showed no evidence of any hybridisation between human and mouse or rabbit sub-units. It is concluded that during direct cell interaction, enzymically active β-glucuronidase is transferred directly from donor lymphocytes to deficient fibroblasts by a mechanism, previously shown not to involve normal receptor mediated endocytosis.