INVIVO IMMORTALIZATION OF MURINE PERITONEAL-MACROPHAGES - A NEW RAPIDAND EFFICIENT METHOD FOR OBTAINING MACROPHAGE CELL-LINES

Although several murine macrophage (mphi) cell lines from different si tes have previously been obtained by in vitro infection with the J2 mu rine retrovirus, which carries the v-raf and v-myc oncogenes, it was n ot possible to immortalize thioglycolate-elicited peritoneal macrophag es (Pmphis) by this in vitro procedure. A technique utilizing in vivo injection of the J2 virus has been developed to overcome this problem. The J2 virus immortalized Pmphis in a very efficient manner in vivo b ecause no exogenous growth factors were required for the in vitro prol iferation of these cells and numerous continuous cloned cell lines wer e readily established. In contrast, Pmphis obtained from uninfected mi ce or Pmphis infected in vitro with the J2 virus did not proliferate. The in vivo immortalized cells had many of the morphological and funct ional characteristics of mphis. Analysis of two of the clones, PMJ2-PC and PMJ2-R, demonstrated intracellular expression of the product of t he v-raf gene, presence of mphi-associated cell surface antigens, inte rleukin-6 secretion induced by lipopolysaccharide, and biological resp onse modifier-induced cytotoxic activity against tumor cells. In addit ion, one of the clones, PMJ2-PC, constitutively expressed major histoc ompatibility complex (MHC) class II antigens, and in the other clone, PMJ2-R, MHC class II antigen expression was induced by recombinant mur ine interferon-gamma. This method of utilizing the J2 virus in vivo re presents a novel technique for obtaining hematopoietic cell lines from cells that are difficult to immortalize in vitro.