Razi Journal of Medical Sciences

Among immune system components natural killer (NK) cells are the first line of defence against tumor cells. The decreasing activity of these cells can be associated with carcinogenesis, in situ tumor growth and metastasis of different cancers, viral infections, immunodeficiency syndroms and autoimmune diseases.

In this study natural killer activity of peripheral blood mononuclear cells (Effector cells) against K562 cell line (Target cells) in clinically and histologically proved cases of nine esophageal, seven breast, six rectum, two melanoma and two stomach cancer patients was assessed concurrently with 31 sex and age mathed controls.

The patients did not have any treatment (chemotherapy, rad iotherapy, surgery and else) previously.

Measurement of N.K activity was carried out using two effector: target (E:T) proportions of 50:1 and 10:1 prior to coculture with effector cells, the target cells were labelled with 51Cr, and after coculturing the amount of free 51Cr was measured using a gamma counter. The percentage of specific lysis (or NK activity) in different cancerous patients (35 ±2%) was statistically (student t test) lower than the value obtain in normal persons (69±1.5%) , (p<0.0001).

This reduction in NK activity can be the cause of tumor cell growth or a consequence of direct or indirect effects of tumor cells on the balance of natural immune system.