It should be stated, there exist many abnormalities of monocytes function in HD patients, while examined in vitro. Their biological significance in vivo remains to be elucidated. The disturbances of monocyte-macrophage system certainly influence the immunoregulation mechanism, especially T-cell-macrophage cooperation and this way augment the immune deficite observed in patients with HD, increase their susceptibility to infections and may be an additional factor favoring tumour dissemination, particularly in the advanced stages of the disease.