Isolation of rabbit IgA antihapten antibody and demonstration of skin-sensitizing activity in homologous skin

Heterogeneity of allergens from, and homocytotropic antibody to, a gastro-intestinal nematode of rabbits

More than one homocytotropic (reagin-like) antibody response in rabbits was demonstrated to a natural parasite, Trichostrongylus retortaeformis, a nematode which occurs only in the gastro-intestinal tract. The responses were detected by the homologous passive cutaneous anaphylaxis (PCA) reaction, three days after skin sensitization. Isoelectro-focusing of aqueous worm larval extract provided fractions in which more than one allergen was recognized. The separate allergen-homocytotropic antibody reactions were found with whole sera from different animals which had been infected by larvae of different ages, but it was not shown in this work whether this difference caused the separate antibody responses.

Specificity of fixation loci for homocytotropic antibodies

The heat-stable, homocytotropic antibody synthesized by guinea pigs to highly purified dextran has been studied by passive cutaneous anaphylaxis (PCA). Antibody arising in single guinea pigs was found to give PCA in some homologous recipients but not in others. Data are presented which indicate that the antibodies are bound in the skin of some animals to a greater degree than in that of others. This suggests some type of variability, perhaps allotypic, in the Fc portion of these immunoglobulins which relates to specificities of the loci where Fc becomes fixed in skin.

Determination of antibody class in a system of cooperating antigenic determinants

19S and 7S memory is analyzed in a system of cooperating antigenic determinants. Cooperation occurs in the induction of both 19S and 7S secondary antibodies, and for both responses carrier specificity can be entirely accounted for by presensitization of the animal to carrier determinants. The class distribution of secondary anti-hapten antibody depends on the dose of the hapten primary-carrier conjugate used for priming, and on the time interval between priming with the hapten primary-carrier conjugate and secondary injection. The conditions of priming with the secondary carrier influence the extent of the secondary response but not the class distribution of secondary antibody. The data confirm the cooperation hypothesis of antibody induction. Specifically, we interpret them to mean that in hapten-carrier cooperation, the hapten-specific memory cells are predetermined for the class of the emerging antibodies. Together with the hapten-specific memory cells, the carrier-specific helpers are responsible for the extent of the secondary response.

Enhancement of rabbit homologous skin sensitization by chemical modification of anti-DNP antibody

Succinylation of a γG derived from an hyperimmune rabbit anti-DNP-BSA serum resulted in the increase of homologous skin-sensitizing activity as measured by the Praustnitz—Küstner technique. Increasing the degree of succinylation yielded a higher percentage of substituted free amino groups and greater anodal electrophoretic mobility. The skin-fixing and hapten-binding activities of the modified preparation were reduced. Further results of succinylation were a loss of both precipitating and complement-fixing activities and a decrease in the heterologous (guinea-pig) PCA activity.

Several possible explanations of the enhancement of the homologous skin-sensitization are suggested.

Suppression of reagin synthesis in rabbits by passively administered antibody

The formation of rabbit antibodies, capable of sensitizing homologous skin, (reagins), was completely inhibited by passive administration of serum containing large quantities of 7S antibody 24 hours before or after antigen injection. No evident effect on reagin formation was noted when passive antibody was administered 8 days after antigen injection although some suppression of agglutinating antibody synthesis was observed. In rabbits not treated with passive antibody the injection of haemocyanin resulted in the formation of reagins reaching maximum serum concentrations 1 and 3 weeks following antigen injection. Both the `early' and `late' reagins persisted for a long time in the skin of injected rabbits, they appeared to have similar molecular size and both were devoid of PCA activity when injected into decomplemented rabbits. There was some indication that the `early' reagins may be more heat-labile than the `late' ones. A secondary reagin response was obtained in several animals which had shown a primary reagin response, but not in rabbits with inhibited primary response. The reagins formed in response to secondary antigen stimulation disappeared rapidly from the circulation, simultaneously with the rise in agglutinating antibody titres.

The possible implications of the findings for the immunological treatment of allergic disorders is discussed.

Heavy and light chain allotypic markers on rabbit homocytotropic antibody

Evidence has been presented that rabbit homocytotropic antibody prepared against ovalbumin bears allotypic markers of both group a (heavy chain) and group b (light chain). This was shown by specific removal of activity in passive cutaneous anaphylaxis assays by anti-allotype immunoadsorbents. The homocytotropic antibody has properties which indicate that it belongs to a new class of rabbit immunoglobulin. These results demonstrate that this newly described class possesses the allotypes of both groups a and b, as has been previously shown for other rabbit immunoglobulin classes.

Rabbit homocytotropic antibody. A unique rabbit immunoglobulin analogous to human IgE

Rabbits immunized with egg albumin produce a homocytotropic antibody. The antibody is identified by its ability to produce passive anaphylaxis in rabbit skin. The time of appearance of this antibody, its persistence and recall after booster injections depends, in part, on the route of immunization and the adjuvant employed. The physicochemical characteristics of the homocytotropic antibody obtained was similar regardless of the immunization schedule used. The anaphylactic activity of these antisera showed some heterogeneity when chromatographed on diethylaminoethyl (DEAE)-cellulose, but all fractions were inactivated by heating and absorption with a specific antisera. The anaphylactic activity could be separated from rabbit IgG and IgA, and was not blocked by absorption with antisera specific for these classes of immunoglobulins. Anaphylactic activity was completely removed by absorption with a specific antiserum which did not react with any of the known rabbit immunoglobulins. The passive cutaneous anaphylaxis titer of a rabbit serum containing homocytotropic antibody was reduced by 50% after absorption with an antisera (anti-FcND) specific for human IgE. On the basis of these distinctive physicochemical characteristics, it is concluded that rabbit homocytotropic antibody represents a unique class of rabbit immunoglobulin, analogous to human IgE.

Heterogeneity of the antibody response to thyroglobulin: effects of 6-mercaptopurine

Treatment with 6-mercaptopurine delayed synthesis of both IgG and IgM anti-thyroglobulin antibodies after primary immunization. Synthesis of IgG, but not IgM, was inhibited. A third Ig, of β mobility, was detected during the secondary response and appeared to be inhibited in the rabbits treated with 6-mercaptopurine during both the primary and secondary responses. Homocytotropic antibody activity was only slightly affected by 6-mercaptopurine treatment.

Treatment with 6-mercaptopurine during both the primary and secondary responses had relatively little effect on the magnitude of the secondary response, although higher levels of precipitating antibody were observed for rabbits treated with 6-mercaptopurine during only the primary response. These results suggest caution in the extrapolation of the experimental results obtained with 6-mercaptopurine (and perhaps other metabolic inhibitors) to diverse experimental systems.

Formation of rabbit reaginic antibodies to protein and hapten-protein conjugates

The capacities of BSA and DNP—protein conjugates to evoke reagin formation in rabbits were compared. Reagins to DNP generally appeared earlier and disappeared more rapidly from the circulation than did anti-BSA reagins. Initial formation of reagins proceeded with a logarithmic phase indicating a doubling time of 7–8 hours. Booster antigen injections resulted in some cases in a reagin response after a shorter latent phase than that observed after primary immunization. A secondary reagin response was more readily evoked in rabbits with low titres of agglutinating antibodies than in those with high titres. Anti-DNP reagins were demonstrable in a higher percentage of the injected rabbits than were anti-BSA reagins. The two types of reagins were equally sensitive to heat and 2-mercaptoethanol. A positive correlation between serum levels of anti-DNP but not anti-BSA reagins and agglutinating antibodies was demonstrated. Some evidence that a low antigen dose was more efficient than a high dose in evoking reagin formation was obtained. Treatment of rabbits with 6-mercaptopurine during the 1st week following antigen injection resulted in an increased latent phase and an enhancement of the production of anti-BSA reagins and some suppression of the formation of anti-DNP reagins.

Immunological induction of increased vascular permeability. I. A rabbit passive cutaneous anaphylactic reaction requiring complement, platelets, and neutrophils

Passive cutaneous anaphylaxis (PCA) reactions were produced in rabbits by antibodies to bovine serum albumin. Two types of antibodies were found, each inducing increased vascular permeability, but by means of different mediation systems. One of these antibodies required the presence of complement, platelets, and neutrophils for the induction of the PCA reaction, which was inhibited by antihistamine. This antibody was heat stable, sedimented in the 7S region, and was found in both fast and slow electrophoretic fractions of rabbit gamma-globulin. Homocytotropic antibody was also detected. The PCA reactions induced by this type of antibody did not require platelets or neutrophils and were not inhibited in rabbits depleted of C3 with cobra venom factor. The lesions were, however, prevented by administration of antihistamine.

Heterogeneity of the antibody response of rabbits immunized with acrylic particle-bovine serum albumin complexes

Prolonged synthesis of IgM, as well as increased levels of IgG and another, probably IgA, class of antibody to bovine serum albumin was observed after multiple injections of rabbits with antigen-coated acrylic particles. IgM and IgG antibodies appeared to be synthesized nearly simultaneously. The class of antibody designated as IgA appeared to be synthesized later or after more extensive antigenic stimulation. Detection of IgA was often difficult since many of its properties were intermediate to and overlapped with those of the other two major immunoglobulin classes. The data presented, therefore, indicated additional, commonly occurring heterogeneity of the antibody response of the rabbit to particle-bound antigen. It is likely that similar patterns of response may also occur after immunization by other means. Therefore, the occurrence of another class of immunoglobulin must be recognized if the full scope of the antibody response of the rabbit is to be elucidated further.

Molecular forms of rabbit antibody synthesized during the primary response to human albumin

Rabbits were injected intravenously or into the hind footpads with 10 mg alum-precipitated human serum albumin or this antigen in complete Freund's adjuvant. Passive haemagglutination, antigen-binding, precipitation, radio-immunoelectrophoresis and passive cutaneous anaphylactic reactions were applied to the assay of antibodies in sera and in ultracentrifugal, electrophoretic and chromatographic fractions of these sera. The γM and γG antibodies appeared simultaneously in the blood on day 6 after immunization. The γM antibodies were detected most readily by haemagglutination, but also by radio-immunoelectrophoresis. These antibodies were not detected by antigen-binding, by precipitation, or by passive cutaneous anaphylaxis. The small amounts of γG antibody that first appeared on day 6 were detected by antigen-binding and radio-immunoelectrophoresis. On day 8 these γG antibodies were revealed by haemagglutination, precipitation and passive cutaneous anaphylaxis. A third type of antibody with the mobility of a β₁-globulin was identified by radio-immunoelectrophoresis in concentrated electrophoretic fractions prepared from 10 to 25 ml of day 6 antisera.

The data are discussed with regard to the validity of the postulated sequential synthesis of γM and γG antibodies, to the cellular origins of antibodies, and to the methods for demonstrating different classes of antibodies.

Non-precipitating rabbit antibody to hapten: purification and properties

Anti-azo benzene sulphonate antibodies were isolated from rabbit serum using two different methods in succession: first specific precipitation, and then specific absorption to a solid immunoadsorbent. The two purified preparations of antibody differed considerably in their ability to precipitate with antigen. It was found, however, that the non-precipitating antibody could largely be coprecipitated with antigen when mixed with precipitating antibody. Hapten binding experiments carried out on both preparations of antibody indicated that the κ_A values were of the same order of magnitude. The difference in method of preparation used was shown to have negligible effect on the hapten binding properties of the two antibodies. The important differences between the non-precipitating and precipitating antibodies were: (1) electrophoretic mobility, and (2) antigenic specificity. The precipitating antibody was identified as a γG-globulin, the non-precipitating variety as probably a γA-globulin. These results are compatible with the presence of a greater number of ionizable groups, i.e. potentially hydrophilic groups, on the non-precipitating antibody. The consequent higher molecular charge of the non-precipitating antibody may be an important factor in the failure of this antibody to precipitate with antigen.

Rabbit anaphylactic antibody

Antibody capable of sensitizing rabbit skin for passive cutaneous anaphylaxis is produced in the rabbit as early as 6 to 7 days following antigenic stimulation. It reaches peak activity around the 9th day and is gone by the 3rd wk. The antibody is heat labile, sensitive to treatment with mercaptoethanol, non-precipitating and does not fix complement. In order to demonstrate PCA activity a latent period is required of from 48 to 72 hr after introduction of the antibody into the rabbit's skin; the activity can persist for at least 17 days. It has a faster electrophoretic mobility than rabbit gammaG-globulin, and is eluted somewhat earlier than gammaG-globulin from Sephadex G-200, although distinctly after gammaM-globulin. No relationship was demonstrated between the rabbit PCA activity and the hemagglutinating activity found in the same sera. The rabbit anaphylactic antibody differs in almost all properties studies from the rabbit 7S antibody capable of sensitizing guinea pigs for PCA which arises at the same time. This latter antibody found early in immunization had properties which were indistinguishable from those described for the rabbit 7S antibody giving PCA in the guinea pig found in late hyperimmune sera.