Effect of recombinant human granulocyte colony-stimulating factor on Pneumocystis carinii infection in nude mice.

Repeated subcutaneous (s.c.) injections of recombinant human granulocyte colony-stimulating factor (rhG-CSF) to Pneumocystis carinii (P. carinii)-infected balb/c nude (nu/nu) mice had no effects on the number of the P. carinii cysts in the lungs, despite neutrophilic infiltration in the tissues and a marked increase in blood neutrophil count. This finding indicates that neutrophils in the absence of T cells do not play an important role in the killing of P. carinii. However, survival periods of the rhG-CSF treated mice seemed to extend to some extent compared with the controls presumably because of the prevention of mixed bacterial infections.