Generation and characterization of a microglial cell line, MG5, derived from a p53-deficient mouse.

We have established a cell line cloned from primary-cultured microglia obtained from p53-deficient mice. The cell line, MG5, could be grown in astrocyte-conditioned medium and has been maintained for more than a year. MG5 cells are immunocytochemically positive for Mac-1 and F4/80 antibody and express the major histocompatibility complex (MHC) class I antigen, leukocyte function-associated antigen-1, leukocyte common antigen, and intercellular adhesion molecular-1 mRNA. Interferon-gamma enhanced the expression of MHC class II antigen mRNA in MG5 cells. We previously identified a novel calcium-binding protein, Iba1 (ionized calcium-binding adapter molecule 1), which is highly and specifically expressed in cultured microglia. Iba1 protein was also immunocytochemically demonstrated in MG5 cells. The cells retained non-specific esterase activity, 5'-nucleotidase activity, acid phosphatase activity, and phagocytic ability. Like primary cultured microglia from wild-type mice, MG5 cells released nitric oxide in response to lipopolysaccharide, and actively proliferated in the presence of mitogenic factors such as macrophage-colony stimulating factor (M-CSF), granulocyte/macrophage-CSF (GM-CSF), and interleukin-3 (IL-3). Tyrosine-phosphorylation of M-CSF receptor in MG5 cells was induced by the addition of M-CSF or astrocyte-conditioned medium. These findings indicate that MG5 cells preserve the morphological, biochemical, and physiological properties of primary-cultured microglia well. The MG5 cell line will be a useful tool for studying microglial function.