[Effect of the tumor-bearing host serum on the leukocyte adherence inhibition reaction mediated by immune RNA].

51Cr-labelled leucocyte adherence inhibition (LAI) assay was used as an index to study the activity of xenogenic immune RNA (iRNA) in inducing normal LACA mouse spleen lymphocytes to mediate tumor specific response in vitro. RNA was extracted from the spleen and lymph nodes of the guinea pigs immunized by S180 or H22 ascitic tumor cells and from those of the normal guinea pigs. Extracts of S180 or H22 tumor cells and that of normal LACA mouse livers were prepared by PBS method respectively. Three kinds of RNA and three kinds of cell (tissue) extracts were grouped into nine combinations. A defined number of 51Cr-labelled lymphocytes was added to each group. The results showed that only in the combination of two kinds of iRNA and the corresponding tumor cell extract, adherence of normal lymphocyte was significantly inhibited. Serum from tumor bearing host inhibited LAI reaction mediated by iRNA. The "blocking" effect was specific since it occurred only when the serum and tumor extract in the reaction system were taken from the same tumor-bearing donor.