Host-defense mechanism will be composed of nonspecific protective elements and antigen-specific immunity capable of participating in the elimination of foreign materials with or without non-self antigenic determinants, cancer cells with or without tumor-specific antigens, wasted or damaged self components and overproduced self components. Studies on the host defense have been reactivated recently to establish a new field in biological scinece. One of characteristics of such studies may be an elucidation of the sequential process in the contribution of varions protective elements to the elimination of foreign materials or unusual self components. Our group has performed studies to find out new protective elements or new regulatory systems as follows and to compose the sequential process on the basis of new findings.
1. Proposal of“primitive T cell response”as a new entity which shows several characteristics distinct from those of classical immunity of clonal nature and covers the time gap between the nonspecific resistance and clonal immunity.
2. Elucidation of T cell recruitment from the thymus in response to the requirement for host-defense which is involved continuously in the elimination of foreign materials.
3. Elucidation of local differentiation or activation of effectors by which host-defense mechanism can be expressed selectively at the site where foreign materials or unusual self components have to be eliminated.
Further studies in this field will be conducted to establish new simple therotetical backgrounds into which new findings of diversity can be incorporated.
