Methotrexate inhibits polymorphonuclear leucocyte chemotaxis in psoriasis.

Six patients suffering from widespread psoriasis were treated with 20 mg methotrexate (MTX) intramuscularly and the chemotactic activity of peripheral polymorphonuclear leucocytes (PMN) was measured before and after treatment. The modified Boyden chamber method was used and C5a, FMLP, casein and autologous fresh serum served as chemotaxins. Following MTX the chemotactic migration of PMN was inhibited by more than 50% for 2 days and slowly recovered within the following 5 days. The inhibition was present with all of the four chemotaxins used. The results demonstrate that treatment with low dose MTX in patients with psoriasis causes a profound inhibition of PMN function. These findings support the idea that PMN play an important role in the pathogenesis of psoriasis.