Essential fatty acid deficiency symptoms include immune system depression and a general state of inflammatory inhibition. CP 24,879 is an inhibitor of arachidonic acid biosynthesis acting via the inhibition of .DELTA.5/.DELTA.6 desaturase. Mice injected with CP 24,879 at 3 mg/kg had a reduction of liver arachidonate content of approximately 50%. Murine mastocytoma cells treated with 5 µM CP 24,879 showed increased mead acid content and nearly complete ablation of LTC4 synthesis, consistent with a desaturase inhibition-induced state of essential fatty acid deficiency.