Cross reactivity between the antigens of Periplaneta americana and Triatoma infestans.

The cockroach Periplaneta americana (Pa) and the reduviid Triatoma infestans (Ti) are two very common insects in Argentina that pollute indoor and outdoor environments. They are also strongly immunogenic in animals and in atopic men. Several immunological methods such as serological absorption procedures, diffusion gel methods and capillary electrophoresis were applied in order to establish the existence of common glycoprotein epitopes in the cockroach and in the reduviid. The presence of specific antibodies (IgG & IgE) were detected in rabbits as well as in human sera. The RAST and RAST-inhibition confirmed the cross-reactivity between these two antigens. Capillary electrophoresis evoked similar patterns among Pa, Ti and the moults of the nymphs of Ti. All these findings have clinical and epidemiological importance.

IgE antibodies against snake venoms.

A similar event was detected in the clinical records of a small group of atopic patients living in the northern provinces of Argentina, i.e., they were bitten by a snake of the Bothrops species (or yarará) during their rural activities (woodcutters, cattle-drivers and farmers). Those who were bitten twice suffered an acute episode of hives and angioedema within 15 minutes after the snake bite. The presence of specific antibodies against Bothrops alternata (Ba) extract was detected by means of RAST for IgE and Ouchterlony and Boyden for IgG. The Ouchterlony also demonstrated crossreactivity among the venoms of the Bothrops species and the positivity of the six fractions obtained by DEAE-cellulose column fractionation against the horse anti-Ba serum. The Ba antigen induced a definite inhibition of the RAST. We presume that hives and angioedema in atopic patients immediately after a second snake bite could be attributed to the presence of a specific IgE antibody against the venom, and must not be misinterpreted with the toxic effects that appear later.

Interstitial pneumonitis induced in guinea pigs by Triatoma infestans antigens.

Data concerning the experimental induction of hypersensitivity pneumonitis in guinea pigs with a Triatoma infestans antigen are presented. Glycoproteins obtained from the chitinous structures of T. infestans (79 kd + 11 kd) were aerosolized daily to guinea pigs during 7 weeks. The presence of specific antibodies (IgG and IgE) was detected by serological techniques; histopathological studies of the lungs showed interstitial infiltrates of macrophages and T-cells. Single non-necrotizing granulomas were seen at the seventh week of the experiment. The results from this animal model suggest that this hypersensitivity pneumonitis is a typical delayed-type reaction due to chronic contact with the heterologous glycoproteins of T. infestans.

Immunochemical properties of the antigens of Triatoma infestans.

Taxonomically related to the cockroach Periplaneta americana (Pa), Triatoma infestans (Ti) is an insect that parasitizes two-thirds of Argentina and acts as a vector for American trypanosomiasis. The glycoproteins obtained by a Sephadex G-150 column fractionation from the whole-body extract prepared with the chitinous structures revealed antigenicity in rabbits, which developed specific IgG after 8 weeks of immunization, as detected by several serological techniques. Atopic patients living in the northern provinces of Argentina--Santiago del Estero and Chaco (endemic area for Ti)--with rhinitis/asthma showed immediate positive skin tests to Ti and its fractions, as well as an IgE-RAST-anti-Ti in 30-36% of them. Healthy nonatopic adults of the same area and other atopics and nonatopics from Buenos Aires (non-endemic area) were selected as controls and showed negative type I skin tests, as well as specific RAST. The existence of common epitopes between Ti and Pa was confirmed by absorption techniques, RAST inhibition, IEF and STIF-RAST. These findings have clinical and epidemiological connotations.

IgE antibodies against Neisseria flavescens.

Bacterial allergy is still a matter of controversy. We sustain that this name should be employed only in the presence of a specific IgE against antigens from bacteria. In 100 atopic patients and 100 healthy controls with Neisseria flavescens in their pharyngeal exudates, we performed type I immediate skin tests with Neisseria flavescens and IgE-RAST throughout 1 year. Positive wheal and flare reactions were elicited in 8 of 100 atopic patients as well as in 3 of 100 nonatopic subjects. IgE-RAST/anti-Neisseria flavescens was found in 6 of the former group and in 1 of the latter. Neither late-phase nor Arthus-like reactions were recorded. Neisseria flavescens is a non-pathogenic commensal of the oropharynx with scarce antigenic properties and seems not to play an important role in these conditions (rhinitis/asthma). Bacterial immunotherapy should be considered only in the presence of specific IgE antibodies with careful selection of the bacteria or their antigens.

Induction of anti-orange antibodies in rabbits.

The capacity of certain foods to cause allergic reactions is well known. The four types of mechanisms that Gell and Coombs described in 1968, are involved in these reactions, although the reaginic antibodies retain the paramount attention of the immunologists. The physiochemical composition of the allergen molecule is the goal of investigators with the purpose to clarify the intrinsic kinetics of antibody synthesis. This paper contributes to the conflicting data about orange allergens especially those obtained from Citrus Aurantium Sinensis and Citrus Silension (CAS and CS, respectively). Glycoproteins were separated by gel filtration through a Sephadex G-50 column. A definite protein peak was obtained meanwhile several hexoses appeared throughout the fractionation procedure. These molecules have adequate physiochemical properties that make them able to trigger the immunological response (molecular weight, definite chemical composition and glycoprotein content). Although CAS and CS have a similar chemical composition a slight inverse proportion of proteins and hexoses was demonstrated between the two classes. Molecular weights were different for CAS (51.500) and for CS (37.000) in comparison with well established protein makers. Ouchterlony revealed two precipitin lines in the CAS-anti-CAS system but none in the CS-anti-CS one. The Boyden technique showed a titre of 1/256 in the first case and only of 1/64 in the second of specific anti-orange antibodies. All the eluted fractions gave negative results although they were concentrated ten times by pre-evaporation. This animal model reinforced the statement that after a long and continuous exposure to orange antigens it was possible to develop specific antibodies. It is assumed that this phenomenon happens in atopic children with it's diagnostic and therapeutic importance.