Production of interleukin-1 receptor antagonist isoforms by microglia in mixed rat glial cells stimulated by lipopolysaccharide

Although the natural interleukin-l receptor antagonist (IL-1Ra) has been sh own to be produced by microglial cells in response to immune stimuli, nothi ng was known about the ability of these cells in primary culture to produce the different isoforms of IL-1Ra, Using RT-PCR, we first confirmed that mi xed glial cell cultures from newborn rats respond to the cytokine inducer, lipopolysaccharide, by synthesizing IL-1Ra mRNA, Using double immunostainin g,we showed that IL-1Ra was detected in microglia but not in astrocytes. Us ing Western blotting, me finally demonstrated that the IL-1Ra1 isoform nas secreted in the supernatant of mixed glial cell cultures, and its productio n increased in response to lipopolysaccharide, The three different IL-1Ra i soforms were constitutively expressed in cell lysates and their levels incr eased after lipopolysaccharide treatment, except for IL-1Ra3, These results point to the ability of microglial cells in primary culture to produce the different isoforms of IL-1Ra.