Effect of stimulation and blockade of mononuclear phagocyte system on the treatment of microfilaremia of Litomosoides carinii in the cotton rat and the jird.

The role of mononuclear phagocyte system (MPS) in the effect of diethylcarbamazine (DEC) for clearing microfilariae of Litomosoides carinii from the blood stream was studied in the cotton rat and the jird, using diethylstilbestrol (DES) for the stimulation of MPS and carrageenan (CGN) for the blockade of MPS. The level of microfilaremia was not influenced by administration of DES subcutaneously or CGN intraperitoneally, indicating that the circulating microfilariae in naturally infected animals were affected neither by the activation nor suppression of MPS. DEC-mediated clearance of microfilariae in the cotton rat was remarkably enhanced by the activation of MPS. Unlike the cotton rat, microfilaricidal effect of DEC in the jird was not influenced by pretreatment with DES. This result corresponds to the fact that the phagocytic activity of MPS was enhanced by DES in the cotton rat, but not in the jird. On the other hand, although the phagocytic activity of MPS was depressed by CGN in the cotton rat, there was no distinct change in the effect of DEC both in the cotton rat and the jird by pre-treatment with CGN, suggesting that CGN-mediated blockade of MPS was a transient phenomenon.