Role of circulating antibodies in the humoral leukocyte adherence inhibition response of lung and breast cancer patients.

A modified leukocyte adherence inhibition (H-LAI) assay has recently been developed in which 0.25% serum from the patient is added to the assay system in combination with the relevant antigen. Trypsinized leukocytes from control persons are used as indicator cells. In the present work, the nature of the humoral factor in serum from breast and lung cancer patients is studied. 3.5 M KCl extracts from the cell lines MCF-7 and Calu-1 were used as breast and lung cancer antigen, respectively. It was found that the humoral factor involved in the H-LAI response was precipitated from the sera by addition of ammonium sulphate to 50% saturation. This factor could be removed by passage through an affinity column with the relevant antigen bound to the matrix. Stable complexes were formed between the humoral factor and the relevant antigen, and could be precipitated by polyethylene glycol. When different anti-immunoglobulins were added to the sera, the humoral factor was specifically removed by addition of anti-IgG antibodies. The data presented indicate that the humoral factor in sera from patients with breast and lung cancer is antitumor antibodies of IgG nature.