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THE CATABOLISM OF HOMOLOGOUS AND HETEROLOGOUS 7S GAMMA GLOBULIN FRAGMENTS.

The catabolism of homologous and heterologous 7S gamma globulin fragments obtained by pepsin and papain digestion was studied in rabbits, guinea pigs, and mice. The elimination from the circulation of I* labeled gamma globulin fragments was followed and the urinary excretion of the total and protein-bound I* activity determined. Evidence is presented that the molecular structure responsible for the catabolism of 7S gamma globulin is located in papain fragment III. The elimination of papain fragment III was slow and closely related to the intact gamma globulin, whereas the pepsin fragment and papain fragments I and II were rapidly eliminated and catabolized in all species examined. Prolonged incubation with cysteine altered papain fragment III as shown by a rapid catabolism of a large portion of incubated fragment III within 24 hours after injection. Small amounts of intact RGG and RGG papain fragment III were excreted as protein-bound I* activity in the urine. On the other hand, large amounts of the pepsin fragment and papain fragments I and II of RGG were excreted as protein-bound I* activity in the urine. The possibility of a molecular structure present in papain fragment III, which may be responsible for tubular reabsorption in the kidney, is discussed. The rate of urinary excretion of fragments obtained from RGG was different from that of fragments obtained from gamma globulin of several other species. In general, small amounts of the pepsin fragment and papain fragment III obtained from gamma globulin other than RGG were excreted as protein-bound I* activity. The amounts of fragment I* excreted as protein-bound I* activity depended on the species in which it was injected, as well as the source of the gamma globulin. The rapid catabolism of the pepsin fragment and papain fragments I or II which bear antibody-combining sites suggest that their use for the prophylactic treatment of tetanus and diphtheria in man is limited.

Animals↗

L-Asparaginase: effect on 7S gamma globulin extents and germinal centers in spleen and lymph-nodes.

Administration of L-asparaginase may cause remission in a high percentage of acute lymphocytic leukemias and lymphomas, either in experimental animals or in human beings. This enzyme is able to depress immune reactions like lymphocyte blastogenesis and delayed hypersensitivity, and to impair gamma-globulin synthesis. L-asparaginase also has antigenic properties, and may cause the formation of anti-L-asparaginase antibodies. This study reports observations on the effect of L-asparginase on the 7S gamma-globulin levels and on the behaviour of the germinal centers in spleen and lymph nodes. It has been found that after administration of low or intermediate doses of L-asparginase, a decrease in the size of the follicular marginal zones occurred. This was accompanied by an enlargement of the germinal centers. Furthermore the spleen weight decreased and the concentration of 7S gamma-globulin diminished slightly. In animals given high doses of L-asparaginase, germinal centers were enlarged even more but marginal zones appeared repopulated although not to the degree of the controls. The spleen weight of these enzyme-injected animals reached almost the normal values, while a statistically significant decrease of 7S gamma-globulin concentrations was found.

Animals↗

THE IMMUNOGLOBULINS OF MICE. II. TWO SUBCLASSES OF MOUSE 7S GAMMA-2-GLOBULINS: GAMMA-2A- AND GAMMA-2B-GLOBULINS.

Two subclasses of mouse 7S gamma(2)-globulins are identified, and are designated gamma(2a)- and gamma(2b)-globulins. They are distinguished from 7S gamma(1)-globulins, gamma(1A) (beta(2A))-globulins, and gamma(1M)-globulins of mouse serum. Antibody activity was detected among the gamma(2a)-globulins and gamma(2b)-globulins of hyperimmune mouse serum. gamma(2a)- and gamma(2b)-myeloma proteins were identified. The genetically determined isoantigen, Iga-1, was present on gamma(2a)-myeloma proteins, but not on gamma(2b)-myeloma proteins. These findings indicate a complexity among the 7S gamma(2)-globulins which must be taken into account in structural, functional, and genetic studies of immunoglobulins.

Animals↗

STRUCTURAL STUDIES OF HUMAN 7S GAMMA-GLOBULIN (G IMMUNOGLOBULIN). FURTHER OBSERVATIONS OF A NATURALLY OCCURRING PROTEIN RELATED TO THE CRYSTALLIZABLE (FAST) FRAGMENT.

1. Detailed physical, chemical, and immunologic studies of a protein closely related to the Fc fragment and heavy chain of G immunoglobulin (IgG), and elaborated by a subject with a lymphoproliferative disorder are presented. 2. The protein, which has a molecular weight of 51,000, was cleaved into two half molecules by reduction and alkylation. 3. The protein has few if any of the antigenic determinants of the antigen-binding (Fab) papain fragment of IgG, and has a striking similarity in its antigenic properties to the Fc fragment. 4. Fingerprint patterns resemble those of the crystallizable (Fc) fragment, and lack several peptides found in the heavy chain. 5. These findings suggest that the Fc fragment may be a real structural unit of IgG, and raise the possibility of the existence of three different types of polypeptide chains in G immunoglobulin.

Amino Acids↗