DISEASE TYPE-ASSOCIATED INCREASES OF THE PLASMA-LEVELS AND LIGAND EXPRESSION FOR NATURAL ALPHA-GALACTOSIDE-BINDING OR BETA-GALACTOSIDE-BINDING IMMUNOGLOBULIN-G SUBFRACTIONS IN PATIENTS WITH LUNG-CANCER

The presence of natural carbohydrate-binding antibodies may play a rol e in host defence against malignant cells in addition to elicitation o f an immune response by artificial carbohydrate antigens. Human serum contains immunoglobulin G(2) (IgG) fractions with selectivity to alpha - and to beta-galactosides, respectively, irrespective of the type of blood group of the donor. To determine whether these naturally occurri ng subfractions may have any relevance for tumor disease control, thei r binding to malignant cells was ascertained by cytofluorimetric assay s in vitro with a number of human tumor cell lines of different histog enetic origin. The affinity of cell binding was comparable to that of binding to lactosylated or melibiosylated neoglycoconjugates as model ligands in solid-phase assays and K-D values were found to be in the r ange of 5-300 nM. Cross-reactivity of the anomer-selective subfraction s to the other type of ligand was observed to be rather low. When the IgG contents of plasma samples of patients with diverse types of lung cancer were assessed, the concentrations of both galactoside-binding i mmunoglobulin G subfractions were significantly increased in associati on with presence of small cell lung carcinoma and of metastatic lesion s to the lung without any marked change in the overall IgG plasma leve l. Such an apparently general enhancement was seen for patients with a denocarcinoma and included both subfractions with no impact on their p ercentage in the total IEC content. When detergent extracts of tumor a nd tumor-free specimens of the same patient were analyzed with the aff inity purified antibody subfractions to comparatively determine ligand presentation, increases in sugar-inhibitable binding were especially noted for the tumor tissue of small cell lung carcinomas and apparentl y tumor-free samples of cases with lung metastasis. Material from othe r types of lung cancer revealed no significant indication for disease- related alterations with the exception of carcinoids. These data demon strate that plasma levels and ligand expression for two types of natur al galactoside-binding immunoglobulin G fractions can show nonuniform responses in patients within the class of lung cancer. They encourage to deliberately monitor these parameters of the natural carbohydrate-d irected antibody fractions in cancer patients with various types of di sease to clarify the clinical significance of respective malignancy-as sociated changes.