COMPLEMENT EXPRESSION ON ASTROCYTES AND ASTROCYTOMA CELL-LINES - FAILURE OF COMPLEMENT REGULATION AT THE C3 LEVEL CORRELATES WITH VERY-LOW CD55 EXPRESSION

Primary fetal human astrocytes and an astrocytoma cell line, U373-MG, expressed membrane cofactor protein (CD46), CD59, and low levels of de cay-accelerating factor (CD55). Astrocyte CD55 was capable of regulati ng C3 deposition on the cell surface; albeit at a lower level than pri mary human fibroblasts. Negligible complement mediated lysis of primar y astrocytes and the U373-MG cell line was observed, even when large a mount of astrocyte-specific, complement-activating antibodies were bou nd to the cells. Blocking the function of CD59 on astrocytes resulted in a > 90% cell lysis, while equivalent lysis of fibroblasts could onl y be achieved with additional blocking of CD55.