AMEBOID MICROGLIAL RESPONSE FOLLOWING X-RAY-INDUCED APOPTOSIS IN THE NEONATAL RAT-BRAIN

The phagocytic response following X-ray-induced apoptosis in the neona tal rat brain was examined by immunohistochemistry with the antibodies OX-6 and OX-42 which recognize MHC class II antigens and the CR3 comp lement receptor, respectively. Few OX-6-immunoreactive cells were obse rved in control rats, and in rats irradiated at postnatal day 2 and ex amined during the first 2 postnatal weeks. However, a transient increa se in the number of OX-42-immunoreactive amoeboid microglia, containin g large numbers of apoptotic cells, occurred at 6, 24 and 48 h after i rradiation when compared with age-matched controls. These results show that X-ray-induced apoptosis promotes a short-lasting phagocytic resp onse.