Bacteriophage MS-2 in the immune response.

Several aspects of the immune response to bacteriophage MS-2 were studied. In thymectomized, irradiated and bone marrow-reconstituted (TXBM) mice, the response was normal when a high dose of antigen was used. With a 50-fold lower dose of MS-2, the response was impaired, indicating a T-cell involvement in antibody formation. More evidence for the (partial) T-cell dependence of MS-2 was obtained from experiments with anti-thymocyte serum or cyclophosphamide-treated mice. (3H)-thymidine incorporation experiments demonstrated that both B and T cells were active upon in vitro stimulation with MS-2. The dose of MS-2 which was able to induce a normal response in TXBM mice, proved to be optimal for both sensitization and elicitation of a DH. It is concluded that MS-2 is a thymus-dependent antigen which is only thymus independent in high doses.