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Biomedical subjects

R I Lopez

Publications and source records attributed to R I Lopez.

13 recordsLinked to original sources
PubMed1998

Reactivity to recombinant house-dust-mite allergens in asthma and rhinitis in a tropical environment.

BACKGROUND: House-dust mites contain components that are allergenic in mite-sensitive patients, and a number of these have been produced in recombinant form. METHODS: In the present study, we evaluated by skin prick testing the positivity to native Der p 2 and recombinant Der p 2, Der p 5, and Der p 7 allergens of Dermatophagoides pteronyssinus in patients with rhinitis, asthma, or a combination of these diseases, who were positive to whole-mite extract. RESULTS: In all patients, the positivity to both native and recombinant Der p 2 was high. In patients with either rhinitis or asthma, the reactivity to Der p 5 and 7 was significantly lower than to Der p 2. However, in patients with combined disease, the positivity to the minor allergens was almost as high as that to Der p 2. CONCLUSIONS: These results raise the question of whether patients with combined allergic rhinitis and asthma, when compared to those with either of these diseases alone, are predisposed to react to a wider range of mite allergens, or, inversely, whether patients who respond to the minor allergens are more susceptible to suffering the combined disease.

Administration, Inhalation↗
PubMed1993

Allergic reactivity of children of different socioeconomic levels in tropical populations.

Widely variable prevalences of allergic diseases have been reported in tropical populations, and this has been suggested to be due to effects of the nonspecific polyclonal stimulation of IgE synthesis caused by the helminthic infections that are endemic in these areas. Since 1980, we have been evaluating the allergic reactivity of different socioeconomic sectors of the population of tropical Venezuela (lat. 2-12 degrees N), and in the present study analyze the overall results obtained in the laboratory evaluation of children (5-15 years of age) belonging to these groups. Children of medium-high socioeconomic level (M-HSEL), who experience occasional helminthic infections, have moderately high total serum IgE levels, and have elevated skin test positivities and specific IgE levels against environmental allergens. Persons of low socioeconomic level, in the urban, and particularly rural situation experience frequent helminthic infection, and have highly elevated total serum IgE levels. In contrast to the M-HSEL, the majority of these children have detectable specific IgE antibody against a variety of inhalant allergens, but relatively few have high levels, and their skin test positivity is also low. In these frequently parasitized persons, evidence of saturation of mast cell Fc epsilon receptors was found by tests of passive sensitization. We propose, therefore, that helminthic parasites have a biphasic effect on allergic reactivity; occasional infections are stimulatory, via their nonspecific potentiation of IgE synthesis against environmental allergens, and frequent infections are suppressive due to the widely polyclonal stimulation that they cause, resulting in both diminished specific antibody production against any given allergen and mast cell Fc epsilon receptor saturation.

Adolescent↗
PubMed1988

Seroprevalence of Toxocara canis infection in tropical Venezuela.

An enzyme-linked immunosorbent assay (ELISA) was used to determine the seroprevalence of Toxocara canis infection in different socio-economic groups of the tropical population of Venezuela. The lack of definitive independent diagnostic criteria for toxocariasis required the establishment of operational upper limits of normality for Toxocara ELISA values, based upon their log-normalized distribution in a presumptive "non-toxocariasis" sub-population. Only 1.8% of urban subjects of medium-high socio-economic level were considered to be clearly positive in Toxocara ELISA, compared to 20.0% of urban slum dwellers, 25.6% rural subsistence farmers and 34.9% Amazon Indians. As the test was performed using excretory-secretory antigen, and under conditions of competitive inhibition by soluble extracts of non-homologous parasites, co-infection by common intestinal helminths, protozoa or other organisms did not give rise to false positive results. However, strong cross-reactivity with Onchocerca volvulus may have influenced the prevalence figure obtained for the Amazon Indians. These results indicate that T. canis is yet another parasite that is widely distributed in economically underprivileged tropical populations.

Adolescent↗
PubMed1987

Allergic reactivity and socio-economic level in a tropical environment.

As some factors associated with the tropical environment can modify the expression of atopic disease, various indicators of allergic reactivity were compared between allergic and non-allergic subjects of different socio-economic level in Caracas, Venezuela (Lat. 10 degrees N). The socio-economic levels considered were high (HSEL), medium-high (MSEL) or low (LSEL). As generally found in temperature climates, in the HSEL the total serum IgE levels of allergic patients were significantly greater than those of non-allergic individuals (geometric means of 274 vs 126 IU/ml, respectively), as were also the specific serum IgE antibody levels (55.6 vs 23.8% positive, respectively, for house dust). These results correlated closely with the skin-test reactivity of these subjects (60.3 vs 17.5% positive for house dust). In this group, the degree of intestinal helminthic infection was low (5.6% positive for Ascaris). In contrast, for the MSEL where the degree of parasitic infection was higher (13.0%), the total serum IgE levels were elevated in both allergic and non-allergic subjects (602 vs 363 IU/ml). Similarly, positivity for specific IgE antibody was high, and comparable between allergics and non-allergics of this group (61.5 vs 54.2%), as was also the case for skin-test reactivity (71.9 vs 60.4%). In the LSEL, parasitic infection was prevalent (47.6%), and the total serum IgE levels were markedly elevated, with little difference occurring between allergic and non-allergic individuals (2269 vs 1981 IU/ml). The positivity for specific IgE antibody was high, and effectively independent of the allergic state (75.6 vs 53.7%), but in contrast the skin test reactivity was relatively low (22.0 vs 9.8%).(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1985

Interrelationships between immediate, intermediate, and delayed cutaneous reactions and their in vitro correlates.

The mutual correlations between immediate, intermediate, and delayed cutaneous reactions, IgE, IgG, or combined IgG, A, and M antibody levels, and antigen- or mitogen-induced lymphocyte transformation were evaluated in a mixed group of allergic or non-allergic individuals. As might be expected, immediate and delayed reactions correlated significantly with IgE antibody levels and lymphocyte transformation, respectively. Intermediate time-course reactions did not correlate with IgG or IgG, A, and M antibody levels, but did so with immediate reactions, thus suggesting their "late phase" nature. Of particular interest was the finding of correlations that do not conform to the classical concept of the mechanisms involved in the generation of the different cutaneous reactions. Significant correlations were found between immediate or intermediate reactions and antigen-induced lymphocyte transformation, and between immediate and delayed reactions. These results are discussed in relation to recent suggestions that factors released from sensitized T cells can mediate early time-course reactions, and that such reactions may contribute to the manifestation of delayed-type hypersensitivity.

Adolescent↗
PubMed1983

IgE in leprosy; effect of a Mycobacterium leprae-BCG vaccine.

Since some previous studies have reported elevated total serum IgE levels in leprosy, that may be associated with the existence of a state of generalized T cell anergy, we undertook a carefully controlled study of this immunoglobulin in such patients before and after treatment with a Mycobacterium leprae-BCG vaccine. We found, firstly, that lepromatous leprosy patients suffering active disease had only a moderate elevation of IgE levels that was not statistically significant when compared to appropriate controls. In addition, multiple injections of the vaccine did not cause alterations in the concentration of this immunoglobulin. We were, therefore, unable to confirm the possible existence of a generalized immunodeficiency in lepromatous leprosy that could cause hyper-production of IgE.

BCG Vaccine↗
PubMed1983

IgE in leprosy.

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Humans↗