The age-related decline in antibody response is transferred by old to young bone marrow transplantation

The immune response declines with age. This decline correlates with thymic involution and involves primarily a loss in T-cell function, whereas humoral immunity is more variably affected. In the current experiments we have measured immunoglobulin synthesis in vitro after mitogen stimulation, and specific antibody response after vaccination. We found that the response to pokeweed mitogen by non-specific immunoglobulin production, and the response to vaccine was shown to be transferred to lethally irradiated young mice by old to young bone marrow transplantation. Both pokeweed mitogen and tetanus toxoid require T-cell help for optimal response, and, therefore, our observations are in accordance with the age-associated decline in T-cell immunity. The finding that young hosts transplanted with old bone marrow produce less antibody than young hosts transplanted with young bone marrow highlights the importance of the decline in cellular function with age.