Effect of methotrexate on phagocytosis and killing of Staphylococcus aureus by human granulocytes.

The effect of methotrexate on the phagocytosis and killing of Staphylococcus aureus by granulocytes from healthy blood donors was investigated in vitro. A concentration of methotrexate of 2.2 x 10(-4) mol/1 (100 micrograms/ml), which is readily obtained on high dose intravenous administration did not decrease the phagocytosis and intracellular killing of Staph. aureus. In addition, granulocytes isolated from patients after termination of 6 h and 24 h high-dose methotrexate infusions showed normal phagocytic activity.