Abstract The present study was designed to compare the efficiency of adoptive transfer of humoral immunity after liver, kidney, and heart transplantation in relation to the number of passenger lymphocytes, and to estimate the risk of a deterimental effect and the chance of a beneficial effect. Hepatitis B virus surface-antigen-vaccinated brown Norway rats (BNs) and AxC 9935 Irish (ACI rats) served as donors, and na Lewis (LEW) rats as recipients. The liver grafts contained 100 times more passenger lymphocytes than heart grafts, and the kidney grafts approximately ten times more, indicated by monoclonal CD45 antibody staining. Transient anti-HBs immunity did occur after transplantation of all three organ grafts. In all rejecting groups, the serum recipient-to-donor anti-HBs titer ratio (R/D ratio) was below 0.10% with heart recipients showing half the level (0.05%) of liver recipients (0.09%). Under immunosuppression, R/D ratio doubled in liver or kidney recipients, but remained unaffected in heart recipients. Immune transfer was most efficient in immune-suppressed liver recipients in the spontaneously tolerant strain combination as indicated by a significantly higher R/D ratio (0.32%) and a longer titer persistence (up to 9 weeks) than in all other groups. Therefore, mainly liver and kidney graft recipients carry a risk, but also a chance of benefiting from the transfer of donor-derived immunity.