Growth inhibitory factor of human alveolar macrophage

The effect of human lung conditioned medium (HLCM) on the DNA synthesis in cultured human alveolar macrophages (HAM) was evaluated. The medium from human lung cultured for 3 days (3d-HLCM) promoted the DNA synthesis as well as the recombinant human GM-CSF does. On the other hand, that cultured for six days (6d-HLCM) did not promote the DNA synthesis but strongly suppressed GM-CSF induced DNA synthesis in HAM. This growth inhibitory effect was also observed when several macrophage like cell lines were cultured with 6d-HLCM. Partial purification of an inhibitory factor on gel permeation HPLC revealed two distinct peaks of activity with molecular weights of 38 kd and 110 kd.