Previous reports have shown that spleen cells from nonimmune adult mice of certain strains do regularly kill Moloney leukemia virus-induced lymphomas in short-term 51Cr release assays. This naturally occuring killer (NK) cell had low adherent properties and had the morphological appearance of a lymphocyte. Still it lacked surface characteristics of mature T or B lymphocytes. In the present report a functional study was carried out, comparing in parallel the NK system, the T-cell killing across an H-2 barrier (anti-P815), and the antibody-dependent cell-mediated chicken red blood cell (CRBC) system. In contrast to the effector cells in the CRBC system, the NK cells were insensitive to erythrocyte antibody complement (EAC) rosette depletion and would pass through nylon wool columns. NK activity was not inhibited by the presence of heat-aggregated human or mouse gamma globulin, in contrast to the strong inhibition noted in the CRBC system. Sensitivity to trypsin pretreatment was noted in the NK system as well as in the immune P815 system, whereas the CRBC system was relatively trypsin resistant. Antitheta plus complement eliminated the anti-P815 activity, but did not touch the NK activity. The present results thus further distinguish the NK cell from cytotoxic T lymphocytes or from antibody-dependent killer cells.

Spleens of normal young mice of certain genotypes contain lymphocytes that can kill strain A-derived YAC-1 and some other in vitro-grown Moloney lymphoma lines in a 51Cr-release cytotoxic test. We have previously shown that mouse strains can be classified as high or low reactors in this test. F(1) hybrids between low- and high-reactive strains are high-reactive. In the present study, strain-A mice and eight different A F(1) hybrids were tested in parallel for their spleen-cell-mediated killing effect in vitro and their ability to reject graded numbers of YAC ascites or in vitro cultivated cells in vivo. There was a clear correlation between in vitro cytotoxicity and in vivo rejection in all tested genotypes. In segregating (A times C57Bl) times A backcross mice, in vivo rejection of YAC cells was H-2 linked. This is in line with the earlier backcross analysis of the in vitro cytotoxicity, suggesting a polygenic control with at least one H-2 linked factor.

Haemagglutination inhibition experiments were carried out with anti-P1, anti-Pk and anti-P sera in an attempt to increase understanding of the chemical, genetical and serological relationships within the P system. The test-substances comprised a glycoprotein with human blood group P1 and Pk activity isolated from sheep hydatid cyst fluid, fragments isolated from the partial acid hydrolysis products of the P1Pk active glycoprotein, glycolipids, monosaccharides and di- and oligo-saccharides of known structure. The trisaccharide alphaGal(1 leads to 4)betaGal(1 leads to 4)GlcNAc isolated from the glycoprotein hydrolysis products, and earlier established as the P1 determinant (Cory et al., 1974), was the only low molecular weight compound that gave strong inhibition with human, rabbit and goat anti-P1 sera. A disaccharide alphaGal(1 leads to 4)Gal, also isolated from the glycoprotein hydrolysis products, failed to react with anti-P1 reagents but inhibited human anti-Pk sera as strongly as the trisaccharide. The glycolipid alphaGal(1 leads to 4)betaGal(1 leads to 4)Glc-Cer (Ceramide trihexoside) and other oligosaccharides containing alphaGal(1 leads to 4)Gal at the non-reducing terminal were also strong inhibitors of anti-Pk sera. Oligosaccharides with terminal alpha-galactosyl residues joined in other positional linkages gave definite, although less strong, inhibition. The inhibition results suggest a close structural relationship between the P1 and Pk determinants and indicate that the specificity of anti-Pk sera is less closely delineated than that of anti-P1. Human anti-P sera differed markedly from anti-P1 and anti-Pk and were not inhibited by any of the compounds containing alpha-galactosyl residues. The glycolipid betaGalNAc(1 leads to 3)alphaGal(1 leads to 4)betaGal(1 leads to 4)Glc-Cer (globoside) strongly inhibited the anti-P sera. The inhibition of anti-Pk and anti-P sera by ceramide trihexoside and globoside, respectively, confirms the observations of Naiki & Marcus (1974) and supports their conclusions that Pk is the precursor of P. The genetic relationship of the P1 antigen to P and Pk is not clear but biosynthetic pathways are discussed that might explain the absence of P1, Pk and P antigens in individuals of the p phenotype.

Systemic and local cytokine environment may modulate the immunogenicity of colorectal cancer cells, and affect anti-tumor immune functions of tumor-infiltrating lymphocytes. We therefore investigated cytokine mRNA expression patterns in tumors and peripheral blood mononuclear cells (PBMC) from patients with colorectal adenocarcinoma. IL-2, IFN-gamma, tumor necrosis factor-alpha (TNF-alpha), IL-4, IL-6, IL-8, IL-10 and IL-1 beta mRNAs in single cell suspension of freshly isolated colorectal cancer tissue were studied by RT-PCR. Frequencies of cytokine gene expression were compared to those in normal colonic mucosa from tumor patients. The frequencies of IL-2, IFN-gamma, IL-4 and IL-10 gene expression were also determined in peripheral blood mononuclear cells from patients with colorectal adenocarcinoma and compared to those of healthy individuals. Tumor samples were more frequently positive for IFN-gamma, IL-2, TNF-alpha and IL-10 gene expression than normal mucosa (p=0.0001, p=0.0118, p=0.001 and p<0.0001, respectively). Frequencies of IL-2 and TNF-alpha gene expressions were significantly higher in tumors with a diameter <5 cm, than in those with a diameter >5 cm. The genes for IL-6, IL-1 beta and IL-8 were commonly expressed in both tumor tissue and normal colonic mucosa. IFN-gamma transcripts were detected in more PBMC samples from patients with colorectal cancer than those from normal controls (p=0.0449). Thus, colorectal cancer tissue is characterized by a specific pattern of cytokine gene expression. It is likely that multiple interactions between pro- and anti-inflammatory cytokines regulate tumor growth and the functional activity of tumor-infiltrating lymphocytes.