MACROPHAGES MICROGLIA AS SENSORS OF INJURY IN THE PINEAL-GLAND OF RATS FOLLOWING A NON-PENETRATIVE BLAST/

The pineal gland of adult rats was examined immunohistochemically and electron microscopically following exposure of the animals to a single blast equivalent to 110 kg TNT explosive. The most dramatic feature i n rats killed at 7, 14 and 21 days after the blast was the upsurge of a large number of macrophages/microglia intensely immunostained with O X-42, OX-18, OX-6 and ED1 antibodies. These antibodies recognise the c omplement type three (CR3) receptors, major histocompatibility complex class I and class II (MHC I and MHC II) antigens and monocyte/macroph age antigens. Cell counts in OX-42 immunostained sections showed a two -fold increase at these intervals but returned to normal values at 28 days. The immunolabelled cells appeared extremely hypertrophic after t he blast when compared with those in normal rats. In the latter and in rats killed at 28 days after the blast, immunoreactive cells were spa rsely distributed. Ultrastructural study confirmed a wider occurrence of perivascular macrophages/microglia after the blast and the cells we re laden with massive amounts of phagosomes resembling degenerating pi nealocyte processes. It is concluded that the seemingly quiescent macr ophages/microglia present normally in pineal gland were activated by t he external blast force. The induced changes including the increase in cell numbers and endocytosis, however, were reversible in longer surv iving animals. (C) 1997 Elsevier Science Ireland Ltd.