Calcium concentration defines two stages in transformation of lymphocytes by Epstein-Barr virus

Lymphocytes from Epstein-Barr virus (EBV) seronegative donors were either stimulated with Protein A or infected with EBV and cultured in growth medium containing a range of calcium levels (700 microM to less than 2 microM available calcium). Three calcium end-points for the proliferation of B lymphocytes were defined: 18 microM for mitogenically-stimulated B cells; 8 microM for a pre-12 h event in EBV transformation and less than 2 microM for a post-12 h event in EBV transformation resembling the end-point for the emergent lymphoblastoid cell line. EBV-infected lymphocytes cultured in calcium-depleted medium expressed the EB virus nuclear antigen and proliferated after addition of calcium chloride. The present study should be useful both in defining the sequence of events in EBV transformation and in studying properties specific to the transformed phenotype.