Busulfan-induced suppression of natural killer cell activity

The effect of repeated injections of busulfan, an alkylating agent, on immune response of CAF1 mice was studied. A single injection of busulfan or acetone (vehicle to solubilize busulfan) acutely suppressed mitogenic and allogenic responses that normalized at two weeks. Repeated injections of busulfan (four injections), on the other hand, showed a transient suppression of the mitogenic responses. Natural killer (NK) activity during the first ten days after busulfan or acetone injections remained normal. NK activity diminished significantly after two injections of busulfan, remained low after four injections, and did not recover within four months of rest. Prolonged suppression of NK activity may be implicated as playing a role in the emergence of T-cell lymphomas in mice injected with busulfan.