Structure and biological properties of immunoglobulins

Immunohistochemical staining of immunoglobulin G in healthy equine, canine, and feline corneas

Objective

Establishing an immunohistochemical approach for semi‐quantitative assessment of the presence of immunoglobulin G (IgG) in equine, canine, and feline corneas.

Procedures

Healthy corneas of horses, dogs, and cats, euthanized because of a fatal disease or an unrecoverable trauma unrelated to and without a history of ophthalmic disease were formalin‐fixed, paraffin‐embedded, and determined to be pathomorphologically healthy by light microscopy. Automated immunohistochemistry was performed using primary antibodies against IgG, biotin‐conjugated secondary antibodies, and streptavidin‐peroxidase, as well as diaminobenzidine for visualization. After counterstaining with hematoxylin, epithelium, stroma, Descemet´s membrane (DM), and endothelium were semi‐quantitatively scored for the presence of IgG on a 4‐grade scale (0 = no, 1 = faint, 2 = medium, 3 = strong staining) by light microscopy.

Results

Corneal specimens of 20 horses (40 eyes) with a median age of 15.5 years (range 2–31 years), 12 dogs (21 eyes) with a median age of 10.0 years (range 4–16), and 13 cats (24 eyes) with a median age of 10.0 years (range 2–18) were included in the study. Different sexes and breeds were represented. In all corneas (100%), significant medium signal intensity in the stroma was observed. Variable immunosignal was obtained in epithelium, DM, and endothelium.

Conclusion

This method reproducibly allows for the detection of IgG in healthy equine, canine, and feline corneas, particularly stroma. Semi‐quantitative results evidence medium presence of IgG in the corneal stroma. Further research is needed to evaluate IgG presence in diseased corneas.

Molecular evolution of IgG subclass among nonhuman primates: implication of differences in antigenic determinants among Apes

The cross-reactivity of five different rabbit polyclonal antibodies to human IgG and IgG subclass (IgG1, IgG2, IgG3, and IgG4) was determined by competitive ELISA with nine nonhuman primate species including five apes, three Old World monkeys, and one New World monkey. As similar to those previously reported, the reactivity of anti-human IgG antibody with plasma from different primate species was closely related with phylogenic distance from human. Every anti-human IgG subclass antibody showed low cross-reactivity with plasma from Old World and New World monkeys. The plasma from all apes except for gibbons (Hylobates spp.) showed 60 to 100% of cross-reactivity with anti-human IgG2 and IgG3 antibodies. On the other hand, chimpanzee (Pan troglodytes and Pan paniscus) and orangutan (Pongo pygmaeus) plasma showed 100% cross-reactivity with anti-human IgG1 antibody, but gorilla (Gorilla gorilla) and gibbon plasma showed no cross-reactivity. The chimpanzee and gorilla plasma cross-reacted with anti-human IgG4 antibody at different reactivity, 100% in chimpanzee and 50% in gorilla, but no cross-reactivity was observed in orangutan and gibbon plasma. These results suggest the possibilities that the divergence of "human-type" IgG subclasses might occur at the time of divergence of Homo sapience from Hylobatidae, and that the molecular evolution of IgG1 as well as IgG4 is different from that of IgG2 and IgG3 in great apes, this is probably caused by different in development of immune function in apes during the course of evolution.

Fragmentation and reduction of bovine secretory component. Preparation of a biologically active fragment and some evidence for a multiple-domain structure

A tryptic fragment (A) of Mr 25000 was prepared from bovine secretory component. The fragment binds polymeric immunoglobulin, although 9 times less effectively than secretory component on a molar basis. The fragment has four buried half-cystine residues and two exposed half-cystine residues. It gives rise to two fragments of Mr 11000-13000 on prolonged digestion with trypsin, and these do not bind polymeric immunoglobulin. It is proposed that fragment A consists of two immunoglobulin-like domains. Bovine secretory component was found to have 9-11 buried half-cystine residues and four exposed half-cystine residues. Reduction and alkylation of the exposed residues decreases the binding of polymeric immunoglobulin by 3-fold. Initial tryptic cleavage of bovine secretory component gives a fragment (Q) disulphide-bridged to a further fragment (T). Fragment Q is similar in size to a three-domain immunoglobulin fragment, and fragment T is similar in size to a two-domain immunoglobulin fragment. The two-domain fragment A is derived from fragment Q by further tryptic cleavage. The results are compatible with the proposal by Mostov, Friedlander & Blobel [(1984) Nature (London) 308, 37-43] that secretory component consists of multiple immunoglobulin-like domains. The results also indicate that optimal binding of polymeric immunoglobulin involves several domains stabilized by an exposed disulphide bridge.

Activation of the alternative complement pathway by the immune precipitate formed with F(ab')2 fragment of human IgG antibody

The complement fixing ability of the F(ab')2 fragment of human IgG was studied using an immune precipitate (Ippt) formed between tetanus toxoid and the F(ab')2 of high-titer IgG antibody against tetanus toxin. A major subclass of the specific IgG antibody against tetanus toxin, which was separated by affinity column chromatography, was identified as IgG1. On incubation of normal human serum (NHS) with the Ippt formed at equivalence, a dose-dependent consumption of CH50, C3 and C5 activities was observed without significant loss of the early acting complement components. A similar consumption of CH50, C3 and C5 activities was found in NHS reacted with Ippt formed at any antigen/antibody ratio. The Ippt formed at antibody excess was more efficient in complement consumption than the Ippt formed at antigen excess. An apparent consumption of C3 and C5 activities was also noted in C4-deficient guinea pig serum treated with Ippt. When Ippt was incubated with Mg2+--EGTA-treated NHS, both C3 and C5 convertases of the alternative pathway were generated on the Ippt. From these results, it was concluded the the F(ab')2 of human IgG antibody, especially IgG1 antibody, when it formed an Ippt with antigen, could activate the alternative complement pathway.

[Lymphocyte membrane receptors mediating recognition of antigens (author's transl)]

The present article summarizes briefly our knowledge of antigen-specific B- and T-lymphocyte receptors. Antigen-specific receptors on mammalian B-lymphocytes are mainly monomeric IgM and IgD consisting of conventional immunoglobulin heavy and light chains. The nature of the T-lymphocyte receptors which can specifically recognize antigens is not yet fully defined but it seems that conventional light chains do not participate in the build up of this receptor. However, T-lymphocytes express two polypeptide chains which bear variable domains sharing idiotypic determinants with the corresponding B-lymphocytes. These Tau chains can bind the corresponding antigen.

Temperature-dependent changes of myeloma immunoglobulin G (K) IVA, Bence-Jones protein (K-type) IVA and its fragments

1. The temperature function of the myeloma IgG(K) IVA, Bence-Jones protein (K-type) IVA and its fragments (Fab(t), Fc'(t), VL and CL) was studied by thermal perturbation difference spectroscopy and circular dichroism. 2. The IgG and Bence-Jones protein studied were found to be capable of a fully reversible structural changes at temperatures between 25 and 35 degrees C. The changes occurring at the higher temperature are accompanied by the screening of the significant part of exposed tyrosine residues. The transition is not accompanied by an appreciable change in the main IgG secondary structure-beta-pleated sheet, according to the CD data. 3. It was found that the temperature-dependent changes of IgG occur in its Fab fragments, the changes of Bence-Jones protein occur in its variable part (VL domains). 4. The temperature changes in the interval 25-35 degrees C are explained by the flexibility of amino acid side chains composed hypervariable loops delineated the "sides" of cavity between variable domains.

The possible pathways of self-organization of immunoglobulin domains

It was proposed that the most probably germ of the beta-structure in globular proteins would be an antiparallel beta-hairpin initiated by the flexibility and/or bend formation of the polypeptide chain between the connected strands. The possible pathways of self-organization of immunoglobulin domains from antiparallel beta-hairpins are computed using well-known kinetic limitations. The most favourable structures corresponding to the greatest number of dehydrated bulky hydrophobic groups are selected. One of the two most favorable structures obtained in such a way coincides with the native tertiary structure of the domains.

Structure and function of the constant regions of immunoglobulins

Immunoglobulins are somewhat unusual in that they are biologically active proteins capable of carrying out several different functions. Thus, they can bind specifically with antigen, activate the complement system, mediate many cytotropic reactions, and act as antigen receptors on lymphocyte membranes.

Modification of antityphus antibodies on passage through the gut of the human body louse with discussion of some epidemiologic and evolutionary implications

Evidence is presented to indicate that proteolytic and perhaps other enzymes of the louse midgut, essential to the nutrition of the louse, perform molecular dissection on the antirickettsial antibodies present in the blood of a typhus-immune host that selectively destroys, along with other functions, the portion of the antibody that determines the only known function by which antirickettsial antibodies may operate in host defense mechanisms, namely, opsonization of rickettsiae for enhanced ingestion by professional phagocytes and subsequent destruction. The epidemiologic significance of these findings is discussed in relation to the progressive destruction of cells that produce digestive enzymes of the louse midgut that occurs with progressive rickettsial infection, and the possibility of a negative feedback mechanism in transmission is introduced. Speculations that involve evolutionary concepts of both convergent and divergent varieties with respect to rickettsiae, potentially operational in a system that consists of an obligate blood-sucking arthropod vector and a vertebrate host capable of adaptive responses to both vector and rickettsial agent, are presented.

Immunoglobulins in the human cornea

We examined 20 corneas of ten subjects to determine the amounts and distribution of immunoglobulins and albumin. Immunoglobulins IgG and IgA were found in all corneas, were at the same level centrally and peripherally, and were at one-half and one-fifth the serum levels respectively. The amount of cornea IgG correlated with serum IgG, but not with IgA. Immunoglobulin IgM was present in five of the ten sets of eyes. No IgM was detected in the central buttons of four of the five sets where IgM occurred in the corneal periphery. Albumin was present in all corneas, but less centrally than peripherally. The cornea contains high levels of antibody proteins.

Antibodies reacting with the glomerular mesangium. Isolation and immunopathology

Antigens of porcine lung were prepared by homogenization and ultrasonic treatment of lung tissue. The antigens were digested by collagenase and trypsin and chromatographed on Sephadex G 200. After immunization of rabbits with certain fractions of the chromatographed material, antibodies could be obtained in rabbits which fixed in vitro and in vivo in the glomerular mesangium of rats, hogs and the human, but not in the basement membrane of glomeruli of these species. Following intravenous injection into rats, the antibodies could be observed in the mesangial area without an apparent loss of antigenicity for 55 days. While 5 days after the application of 20 mg of the anti-mesangial IgG-preparation, there were no glomerular changes histologically demonstrable, after 55 days small amounts of rat-IgG could be demonstrated histochemically within the mesangium. Deposits of rat-complement (C3) could not be demonstrated with certainty. Severe morphological lesions were absent. Rats injected with the same doses of antibody and simultaneously immunized with rabbit-IgG showed a substantially greater deposit of autologous rat-IgG and rat-complement within the mesangial area after 55 days. By histological examination focal and segmental scleroses of the mesangium were determined. A significant pathological proteinuria did not occur. The present model constitutes a new possibility for studying the function of the glomerular mesangium.

Characterization of anti-Aeromonas salmonicida antibodies from coho salmon

Coho salmon (Oncorhynchus kisutch) anti-Aeromonas salmonicida agglutinins were excluded from Sephadex G-200 and their activity was lost after partial reduction and alkylation followed by exposure to 2 M urea. Immunoelectrophoretic analysis of coho antiserum revealed anodic and cathodic populations of immunoglobulin (Ig), and the anti-A. salmonicida antibodies present 12 weeks after parenteral immunization were primarily anodic Ig. Antibodies were specifically purified by dissociation of A. salmonicida cell wall agglutinates with 15% NaCl. The purified Ig was a 17S macroglobulin, and electron microscopy and sodium dodecyl sulfate-polyacrylamide gel electrophoresis revealed that it was composed of four IgM-like subunits. The minimum coho antibody concentration required for visible agglutination of A. salmonicida cells was approximately 0.006 mug of Ig nitrogen/ml.

The binding of haptens by the polypeptide chains of rabbit antibody molecules

1. The binding of haptens by the polypeptide chains derived from two rabbit immunoglobulin G antibodies was examined by gel chromatography and equilibrium dialysis. 2. The gamma chains were examined in a dilute sodium acetate buffer, pH5.4, in which they exist as a monodisperse solution of dimers; aggregation of the protein promoted by some haptens had to be avoided. These chains exhibited variable extents of binding, reflecting the specificities of the parent antibody molecules, usually with only small increments above the binding by gamma chains from normal immunoglobulin G. 3. The light chains existed as an interconverting mixture of monomers and dimers in all buffers of near neutral pH that were examined. They bound small amounts of hapten, again broadly reflecting the specificities of the parent antibody molecules. 4. For both the gamma and light chains the dimeric state appeared necessary for appreciable binding of hapten. Apparently in each case the partners in the dimer interact in a manner analogous to the gamma chain-light chain interaction in the parent antibody molecule, to give a site analogous to the antibody site. This implies that the binding of antigens by isolated chains has a large fortuitous element, providing no reliable indication of their contributions to the original antibody sites.

The relationship between L-chain synthesis and gamma-globulin production

The simultaneous administration of labeled human gammaG globulin and L-chains to subjects has allowed examination of the metabolic relationship between a component part and the whole immunoglobulin molecule. Studies were carried out in a series of control subjects and in a group of patients where substandard production of gamma-globulin was anticipated, i.e., patients with the nephrotic syndrome on chronic Imuran therapy and patients with uremia. Full expression of the plasma decay curve was obtained for both substances, that for L-chain requiring only 4-5 days except in uremic subjects and that for gamma-globulin requiring up to 30-40 days. Urinary excretion of inorganic iodide was also quantitated for 20-30 days. Equilibrium of the extravascular, vascular, and urinary radioactivity from the labeled gammaG globulin was usually not seen during this time interval suggesting more than one site of catabolism of the protein. Excess L-chain poduction was about 45% of the total L-chain production and probably in no instance could account for the low gamma-globulin production seen in certain patients with renal disease.

Idiotype expression and the inheritance of mouse antibody clones

The inheritance of idiotypes was investigated using idiotypic antisera against two monoclonal antibodies to streptococcal carbohydrates derived from A/J mice. Each of the two idiotypes was characterized by a special frequency of expression. One of the idiotypes was expressed in more than 80% of A/J mice, the other in less than 20%. The idiotypes of both antibodies were strain specific and were transmitted to (A/J x BALB/cJ)F(1) hybrid mice. Furthermore, both idiotypes remained associated with the A/J heavy chain C region allotype in (A/J x BALB/cJ)F(1) hybrid mice. The results suggest that idiotypes are specified by allelic V genes, and that the heavy chain idiotype locus is linked to the heavy chain allotype locus.

The complete amino acid sequence of a mouse kappa light chain

The complete amino acid sequence of the kappa-chain of the mouse myeloma protein MOPC 21 was established. The protein was reduced and alkylated with iodo[2-(14)C]acetic acid, and 21 tryptic peptides were isolated, mainly by paper electrophoresis and paper chromatography. Three large tryptic peptides (of 35, 36 and 42 residues), which were difficult to isolate in this manner, were obtained pure and in excellent yields by a combination of Sephadex G-50 gel filtration in 1% (w/v) NH(4)HCO(3) and chromatography on a DEAE-cellulose column in ammonium acetate buffer, pH8.1. Peptides overlapping the tryptic peptides were isolated from a chymotryptic digest. The chain is 214 residues long. Microheterogeneity of two peptides was observed and is believed to be due to deamidation. It was not excluded that such deamidation could occur in serum from which the protein was isolated. The sequence is compared with the sequences of two other mouse kappa-chains, and with the human kappa-chain basic sequences.

Tissue-specific cell-surface antigens in embryonic cells

With the use of antisera prepared in rabbits against suspensions of live embryonic chick tissue cells, qualitative differences in cell surface antigens were demonstrated on cells from different embryonic chick tissues by immune agglutination and immunofluorescence. Unabsorbed antisera reacted with both homologous and nonhomologous cells; thorough absorption of the antisera with heterologous tissues removed cross-reacting antibodies, and the antisera acquired a high degree of tissue specificity. Thus, antiretina cell serum absorbed with nonretina cells or tissues, agglutinated only neural retina cells, and was shown by immunofluorescence tests to react specifically with the surface of retina cells, both in cell suspensions and in frozen tissue sections. Comparable results with antisera against cells from embryonic liver and other tissues demonstrated the existence of tissue-specific, phenotypic disparities in the antigenicities of embryonic cell surfaces, in addition to the presence of cell-surface antigens shared by certain classes of cells, and of antigens common to all cells in the embryo. The results are discussed in terms of the possible involvement of such phenotypic determinants in the specification of cell surfaces, in relation to cell recognition and developmental interactions.

Chemical markers of transplantation individuality solubilized with sonic energy

Images

A new mouse immunoglobulin: IgG3

A new subclass of mouse IgG for which we propose the name IgG3 has been shown to have a mol wt of 150,000 consistent with an L(2)H(2) structure, and is present in normal mouse serum at a concentration of 0.1-0.2 mg/ml. Its molecular weight, low carbohydrate content, glycopeptide analysis, and C-terminal analysis are all typical of the IgG class. The intact protein had a strong tendency to form noncovalent aggregates with itself which were dissociable in acid. Upon papain digestion an Fab fragment of 47,000 mole wt was generated along with an Fc fragment which was insoluble at neutral pH. As for its biology, the protein did not fix complement, was not cytophilic for gammaG2 receptor sites on macrophages, and did not show passive cutaneous anaphylaxis. It was very efficiently transported across the placenta so that its concentration in the newborn was twice that in the serum of the mother, compared to the concentration of IgG1 and IgG2 proteins which were only present at one-third the concentration of that found in the serum of the mother. The Fc fragment of this protein reacted with and was solubilized by the staphylococcal A protein which also precipitated the intact immunoglobulin. In addition, the myeloma protein which was the prototype for this gammaG subclass exhibited binding activity for levan which was localized to the Fab fragment.

Immunoglobulin structure: amino terminal sequences of kappa chains from genetically similar mice (BALB/c)

The amino terminal portion of 20 kappa chains from the highly inbred BALB/c mouse has been examined on an automatic protein sequencer. These proteins can be divided into at least nine groups (subgroups) based on sequence patterns which are so distinct that each subgroup is probably encoded by at least one germ-line gene. The subgroups of mouse kappa chains are generally quite different from those of human kappa chains.