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Carbohydrate molecules connected mostly with covalent junctions to protein chains are called glycoproteins. These carbohydrate molecules are attached to the protein core in different qualities and order. When the protein core is connected with acidic components such as uronic acid or SO4 radicals, they are called proteoglycans. The currently used name "glycosaminoglycan" in this case is not entirely correct. In the living world polymannane structures occur, too. Glycoproteins do not only exceptionally hold acidic groups but they have neuraminic acid derivatives. Tissue, cellular and matrix structures, and mostly all serum "proteins" are mainly glycoproteins. In the everyday clinical practice glycoproteins are mentioned as proteins. Nevertheless, the inadequate use of the concept may cause errors in the attitudes, too. This paper aims to correct this notion, because the term of "glycobiology" has already been expanded to be an independent scientific field. The practical clinical consequences of recent knowledge in this field are also summarized including novel findings on glycoprotein structures and functions. The importance of the quantity of carbohydrates, and their structural arrangements are also presented. In short, significance of glycoprotein-carbohydrate structures, as well as their physiological and pathological roles are reviewed in order to introduce the field of "glycobiology". Orosomucoid and immunoglobulins are discussed separately. Orv. Hetil., 2016, 157(30), 1185-1192.

In the serum of 27 patients with malignant lymphogranulomatosis the authors determined the serum level of glycoproteid-carbohydrate components (hexose, hexosamine, sialin acid, and seromucoid) and the concentration of 11 different glycoproteids. In the early stage of the disease the immunoglobulin level is moderately increased in the serum, whereas a diminution can be observed in stage IV. The concentrations of ceruloplasmin, alpha-2-macroglobulin and orosomucoid were already increased significantly in stage III. The increase did not continue in stage IV. In the final stage of the disease the concentrations of alpha-1-antitrypsin and haemopexin turned out to be increased considerably. A significant decrease in the transferrin level could be registered in stage III with this diminution also continuing in the further course. Changes of beta-C-globulin and haptoglobin concentrations could not be evaluated statistically. The content of carbohydrate components in the glycoproteids will already increase in the early stage of the disease with this increase continuing in the further course. Among histological types there was a more significant increase of immunoglobulins in those forms rich of lymphocytes.

The concentration of IgA, IgG, IgM, coeruloplasmin, alpha-2-macroglobulin, beta-1-C-globulin, transferrin as well as of alpha-2-haptoglobin, orosomucoid and haemopexin has been studied in the serum of patients with disseminated lupus erythematosus, chronic progressive polyarthritis and immunopathological syndromes. The concentration of the carbohydrate components bound to serum proteins was also determined. In disseminated lupus erythematosus, the concentration of IgA, IgG, IgM, coeruloplasmin, and hexose, hexosamine and sialic acid bound to proteins, as well as of seromucoid was increased. In chronic progressive polyarthritis the IgA, IgG, IgM, coeruloplasmin, alpha-2-macroglobulin and beta-1-C-globulin concentration and the carbohydrate components bound to serum proteins rose. In immunopathological syndromes, too, the serum IgA, IgG, IgM, coeruloplasmin, and protein-bound hexosamine and sialic acid levels were increased. Under the effect of treatment, the elevated glycoprotein concentrations usually decrease, but the level of carbohydrate components bound to serum proteins hardly changes. The pathogenic and diagnostic significance of serum glycoproteins is discussed.

In liver biopsy specimens of 45 patients with chronic persistent hepatitis, chronic aggressive hepatitis and liver cirrhosis the number of lymphoid cells and fibroblasts as well as in the sera of the same patients the concentration of IgG, IgA, IgM, alpha-2-macroglobulin and coeruloplasmin have been studied. The number of lymphoid cells and fibroblasts, was significantly elevated in chronic aggressive hepatitis and liver cirrhosis; a close correlation could be demonstrated between the number of the lymphoid cells and the IgG concentration; the serum alpha-2-macroglobulin level changed parallel to the number of liver fibroblasts in chronic aggressive hepatitis and liver cirrhosis.

The sera of 24 patients with chronic aggressive hepatitis receiving combined immunosuppressive therapy were studied for the concentrations of the carbohydrate components of glycoproteins and the IgG, IgA, IgM, alpha-2-macroglobulin, coeruloplasmin, beta-1-C-globulin and transferrin levels over a period of 2 years. Liver biopsy was performed repeatedly in 50% of the cases. On the evidence of the results, combined immunosuppressive treatment is regarded as apt to normalize the serum concentrations of IgG, IgA, IgM and to reduce those of alpha-2-macroglobulin and coeruloplasmin. Among the carbohydrate components of glycoproteins only the amount of hexose was reduced.