Activation of antitumor properties in alveolar macrophages from protein-calorie malnourished rats.

Protein-calorie malnutrition (PCM) was induced by feeding male F344 rats on a 5% casein diet for 7 weeks. At appropriate times, rats from control (20% casein diet) and PCM groups were killed and alveolar macrophages (AM) were obtained by bronchoalveolar lavage. The functional integrity of the AM was determined by measuring their ability to become tumoricidal on treatment with macrophage activators, such as muramyl dipeptide (MDP) or multilamellar liposomes containing MDP or its lipophilic analog, MTP-PE. After 5 and 7 weeks, the numbers of lavaged AM per gram body weight of rats were much higher in the PCM group than in the control group. In week 3, AM from the PCM group showed spontaneous tumoricidal activity against syngeneic tumor cells, but in weeks 5 and 7 they did not. However, AM from PCM rats behaved the same way as controls in their response to activation stimuli in vitro with multilamellar liposomes containing synthetic MDP or MTP-PE. These data show that PCM affects the number of AM, but that AM from rats in a state of PCM become tumoricidal in response to activation stimuli in vitro.