| Themes > Science > Life Sciences > General Biology > Immunology > The Immune System & Disease > Tolerance > The Danger Hypothesis - Matzinger versus Medewar? |
Matzinger has proposed that there is not a special window for tolerance during neonatal life but that whether encounter with an antigen results in tolerance or an immune response is determined by whether the prevailing host environment promotes a response via nonspecific cues 'sensing' danger. She has further suggested that the controlled death process of apoptosis is critical in preventing autoimmunity when old or surplus cells are disposed of. The notion that the normal, default pathway of the immune system is tolerance rather than response is not a new idea to immunologists - antigens usually fail to elicit a response unless given with adjuvants, whose purpose is probably to generate stimulatory cues (cytokines). Recent experiments have shown that not only can adults be tolerised under certain circumstances, but that neonates can make effective immune responses if the antigen is presented in sufficiently immunogenic form. I believe that the supposed conflict between Matzinger and Medewar is rather 'hyped up' and essentially a matter of detail. Neonatal T cells are not intrinsically tolerisable but the systemic neonatal environment does predispose to tolerance. Nevertheless, I think that her hypothesis has drawn the attention of a wider audience to current ideas about tolerance induction and the factors determining immune responsiveness. |
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