Recent studies on space flights suggest that certain T cell immunologic activities are vulnerable to microgravitation. It would be desirable to know the extent to which these changes can be prevented or reversed. Since the changes observed are analogous to the effects of aging on immunity, a brief overview is presented of our current knowledge of age-related changes in immune cells and of the various interventional methods which have been used successfully in preventing the decline with age and in elevating the levels of immune functions of old individuals.