Normalization of the immune status of the human body during prolonged space flight

During long duration space flights a number of unfavourable situations arise due to changes in endogenous microflora and immunologic reactivity of men. It appears very important to develop procedures that can be used to normalize human resistance to infection. Methods of affecting protein synthesis in immune responsive cells are being investigated. It was found that ribonucleic acids stimulated antibody formation. Application of immunological, immunochemical, and isotopic methods confirmed that one of the main factors were ribonucleotides. Their effect is mainly to accelerate the proliferation of immunocompetent cells. Our experiments have shown that a single parenteral injection of a stimulant of such type is sufficient to sustain capacity for accelerated antibody formation for a long time. A search for non-specific stimulants is needed since they can be effectively used in cases of acute and subacute inhibition of immunity. Their use in combination with specific or non-specific activators may be required in chronic inhibition of immune reactions occurring, for instance, in qualitative and quantitative reduction of normal microflora. Our investigations have demonstrated that germ-free animals and animals with reduced microflora exhibit diminished regional lymphatic nodes, underdeveloped lymphoid tissue of Peyer's plaques and other changes. The paper discusses several methods of maintaining antigen balance.