A cloned murine macrophage-like cell line, FC-1, which arose during fusion of a drug-marked myeloma cell line with primary splenic cells was shown to migrate well from capillary tubes both in medium containing 10% horse serum or in serum-free medium containing 0.5% BSA. This cell line was responsive to MIF produced by mouse spleen cells stimulated with either insolubilized Con A or with alloantigens.

Bio Gel fractionation of MIF supernatants showed the same samples to contain inhibitory material for both FC-1 cells and for primary macrophages and that this product had a m.w. of 25,000 to 50,000.

Because the migration of FC-1 was inhibited by MIF prepared and tested in serum-free medium or in plasminogen-depleted serum, migration inhibition must result from the direct interaction of MIF with macrophages rather than indirectly through an activation of serum enzymes. This was confirmed when primary macrophages that require serum were shown both to migrate well and to respond to MIF in plasminogen-depleted serum.

Because of the homogeneity of the cloned FC-1 cell line and its ability to migrate and respond to MIF in serumfree medium, this macrophage-like cell line offers unique advantages for studying the regulation of macrophage functions by products of activated lymphocytes.

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This work was supported by grants from the NSF-PCM 77-25635 and NIH Grants AI 07115, AI 5231, and AI 10702.

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