Upregulation and induction of major histocompatibility complex class I and II antigens on microglial cells in early postnatal rat brain following intraperitoneal injections of recombinant interferon-gamma.

Interferon-gamma when given intraperitoneally by single daily injection into one-day-old rats upregulated the expression of major histocompatibility complex class I antigen on ramified microglial cells in cerebral cortex and induced the expression of major histocompatibility complex class II antigen both on amoeboid and ramified microglial cells present in corpus callosum and cerebral cortex, respectively. In rats receiving single daily injections of interferon-gamma over a period of three consecutive days and killed at the age of seven days, the endothelium exhibited a moderate to weak immunoreaction for major histocompatibility complex class I antigen as detected with the monoclonal antibody OX-18. The immunoreactivity of major histocompatibility complex class I antigen on amoeboid microglial cells was comparable to that of control rats. On the other hand, it was remarkably enhanced on ramified microglial cells and was further intensified with four or six injections of interferon-gamma. In the latter, the endothelial cells also showed a stronger immunoreactivity with OX-18. In rats given three successive injections of interferon-gamma and killed at the age of seven days, 7.5% of amoeboid microglial cells in corpus callosum were induced to exhibit major histocompatibility complex class II antigen as detected with OX-6. An upsurge of the amoeboid microglial cells with major histocompatibility complex class II antigen amounting to about 40% was observed following four and six injections of interferon-gamma. A minimum of four successive injections of interferon-gamma were needed to elicit the expression of major histocompatibility complex class II antigen on ramified microglial cells in cerebral cortex.(ABSTRACT TRUNCATED AT 250 WORDS)