| [ Summary ] |
In adoptive immune surveillance involving T and B cell responses, clones specific to self antigens are silenced through the mechanisms of clonal deletion, clonal anergy, active suppression and so forth, and thus the unresponsiveness to self antigens, i.e., self tolerance, is maintained. In contrast, T/B cell clones specific to foreign non-self antigens develop in the absence of such foreign non-self antigens and are not silenced. Thus, once T/B cell clones specific to a foreign non-self antigen encounter the relevant antigen, they are activated, proliferate and differentiate into antigen-specific immunocompetent T/B cells on one hand and are inactivated resulting in the antigen-specific unresponsiveness on the other. Factors determining these two opposing outcomes are numerous such as the property of antigens, route of antigen invasions, host anatomical microenvironments where the antigen-specific immune responses take place, genetic as well as physiologic backgrounds of the responding host and so forth. In this article, we will deal with the induction of antigen-specific unresponsiveness to the orally ingested antigens, i.e., oral tolerance, from the point of view of the enigmatic features of gut-associated lymphoid tissues(GALT). |