Immunochemistry最新文献

By use of passive cutaneous anaphylaxis it has been shown that the structure necessary for fixation to tissue constitutents (receptors) is on the Fc fragment. Fc fragments from rabbit IgG can inhibit passive cutaneous anaphylaxis in guinea pigs by competition for the receptor. The fixation of the Fc fragment to receptors (on mastcells) was shown also by reverse passive cutaneous anaphylaxis using dinitrophenylated Fc fragments and anti-dinitrophenyl antibodies.

Antibodies against methylated bases were highly specific. In the case of dimethylated bases, antibodies reacted only with the homologous hapten, slightly with the monomethylated bases at the same position and not at all with the original non-methylated base, or with different methylated bases, Antibodies against monomethylated bases are also very specific. They reacted only with homologous hapten and slightly with the original non-methylated base. Antibodies against inosine distinguished it from 6-mercaptopurine riboside which differs from inosine only in that it has a sulfur atom instead of an oxygen atom. 6-Azauridine, which has a different conformation from uridine, reacted very poorly with anti-uridine antibodies. Antibodies against pseudouridine did not react at all with uridine. Antibodies are very powerful tools to determine conformation of coenzymes containing nucleosides or nuclcotides. Using this approach we were able to suggest that ATP, ADP, CoA, UDP, UTP, CDP and CTP are in a folded configuration.

Continuing our research on specific thymocyte antigens, it was shown that one of these antigens is particularly abundant in the cerebellum and a method has been developed lor its isolation. The activity in immune sera against this antigen, obtained with rat cerebellum, was completely absorbed by analogous human or animal preparations. We therefore used the purified antigen from calf cerebellum to immunize rabbits. The advantage of this method is that it does not require absorption of the immune sera since this purified preparation does not contain undesired antigens common to other cells. Labelled antibodies from these sera allowed detection of human or animal T lymphocytes. However, not all injected animals produced satisfactory immune sera. The problem of the immunochemical structure of the antigen is discussed.

The ability of heterologous antibody toward tumor membrane antigens to suppress the growth of a spontaneous adenocarcinoma in tolerant adult and newborn mice was investigated. Preinoculation of specific antibody strongly enhanced the resistance of 12-week-old mice to subsequent tumor challenge. The antibody activity was specific since an unrelated tumor was not affected. It was also age-dependent, since newborn mice were not protected. The mechanisms involved in the suppression of this tumorin vivo are discussed.

Structural studies on the Groups A, A-variant and C carbohydrates of β-hemolytic streptococci indicate that they have in common a polyrhamnose core. The A-variant carbohydrate consists solely of this polyrhamnose structure which has been shown to contain alternating α1, 2-and α1, 3-linked rhamnose units. In agreement with results first published by Heidelberger and his coworkers (Estrada-Parraet al., 1963), the Group A carbohydrate has been shown to containN-acetylgulcosamine residues attached to the 3-position of the 1, 2-linked rhamnose units in this polyrhamnose structure. TheseN-acetylglucosamine residues impart group-specificity to the Group A carbohydrate. The Group C carbohydrate differs from the Group A carbohydrate by having 3-O-α-N-acetylgalactosaminosyl-N-acetylgalactosamine units attached to the 3-position of the polyrhamnose structure. TheseN-acetylgalactosamine disaccharides are capable of inhibiting the binding of Group C carbohydrate to anti-Group C sera and are cross-reactive with the Forssman antigen.

A triple isotype (²²Na,¹³¹I,¹²⁵I) radioimmunoassay method employing microtiter plates and specially designed disposable paperware has been devised. This procedure allows the determination of antibodies to two non cross-reactive antigens simultaneously on large numbers of samples.

Rabbits were immunized with purified phospholipase A isolated by ion exchange chromatography from the venom ofCrotalus durissus terrificus, a South American rattlesnake. As shown byin vitro andin vivo tests, the antiserum was able to neutralize the hemolytic and toxic activities of the purified enzyme, as well as of crotoxin and the crude venom.

Coupling of soluble antigen, such as RIg, to circulating lymphoid cells or red blood cells increased immunogenicity substantially. As little as 0.01 μg RIg per 10⁷ syngeneic cells elicited an antibody response in C57B1/6J strain mice equal to 1300 μg of soluble RIg. About 20 times the amount of soluble RIg induced far less a cellular immune response in guinea pigs than RIg coupled to autologous peripheral blood cells. These cells apparently play a passive role in being able to deliver bound antigen to lymphoid tissues efficiently, thus increasing the probability of interaction between host helper T cells and antigen. This conclusion is based on the following observations: (1) red blood cells, which are not immunologically responder cells, are about as efficient as lymphoid cells; (2) lymphoid cells are not effective as carriers in mice rendered deficient in antigen-specific helper T cells: (3) the antigen coupled to cells must have carrier specificity for host helper T cells.

The effect of cyclic AMP on LAF-induced potentiation of DNA synthesis in PHA-stimulated rat lymphocytes (LAF effect) was investigated. LAF preparations were dialyzed 24-hr supernatants of partially purified rat macrophages and lacked mitogenic properties. Agents that increase cellular cAMP by different mechanisms (l-isoproterenol, prostaglandin E₁, theophylline, and dibutyryl cAMP) were added before during, or after the period of optimal cell sensitivity to LAF. This period began approximately 16 hr after initiation of the cultures and lasted for about 8 hr. Addition of any of these reagents to the cultures during the first 8–12 hr of culture, i.e. before the period of cell sensitivity to LAF, resulted incomplete inhibition of both the PHA response and the LAF effect. Addition at 16 hr or later, though still inhibiting the PHA response markedly, gave insignificant inhibition of the LAF effect itself. Thus occurrence of a LAF effect requires effective lymphocyte triggering in order to reach the period of optimal cell sensitivity to LAF, a process which is sensitive to elevation of cellular cAMP, but the LAF effect on triggered cells is insensitive to cAMP. We conclude that the lymphocytes tested are heterogenous in their sensitivity both to LAF and to cAMP.