Determination of phagocytosis of Leishmania spp. by human polymorphonuclear leukocytes using anti-Leishmania monoclonal antibodies.

Phagocytosis of Leishmania is an early event in the capacity of human polymorphonuclear cells to limit the spread of this infectious agent. We compared two methods to assess the phagocytosis of Leishmania by PMN cells; the first using histochemical staining with Wright or Giemsa, and the second using the immunoperoxidase technique with anti-Leishmania monoclonal antibodies. The quantitative results obtained with either of the cytochemical methods were comparable with the immunoperoxidase technique, but the latter offered the advantage of an easier identification of the intracellular parasites. This improvement greatly reduced the time required to quantify phagocytosis compared to the conventional staining techniques.

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)

An unusual case of hyper-production of IgE, treated by plasmapheresis.

A 15-year-old boy with severe inflammatory skin lesions from an early age was found to have extremely elevated serum IgE levels (up to 376.000 IU/ml). His skin showed positive direct immunofluorescence for IgE and he had peripheral and bone marrow eosinophilia. No evidence for atopic disease was found, but he suffered intestinal helminthic infection of moderate intensity. He showed a somewhat depressed cell mediated immune response but a normal polymorphonuclear function. Various treatments that included anti-inflammatory, anti-allergic, anti-parasitic, anti-mycotic and PUVA therapy did not significantly improve his condition A therapeutic test using plasmapheresis produced marked, though short-lived clinical improvement. We believe that this case might result from the superimposition of the stimulatory effects of intestinal helminthiasis on a background of intrinsic hyper-production of IgE.

High allergic reactivity in a tropical environment.

The prevalence of atopic disease in tropical populations is often considered to be low, and this has been attributed to an immunological modulating effect of intestinal helminthiasis. We, however, report that the frequency of positive allergic history and skin-test reactivity to groups of major environmental allergens is extremely high (43 and 63% respectively) in children in Caracas, Venezuela (Lat. 10 degrees N). These values were statistically significantly greater than in a group of children with a similar age and sex distribution studied in parallel, but having limited or no contact with a tropical environment (29 and 37% respectively). The two groups differed with respect to the sporadic and light intestinal helminthic infections (such as ascariasis) experienced by the Venezuelans, compared to rare contact in the 'non-tropical' group. This was probably the cause of the increased total serum IgE levels of the former children (369 vs 68 iu/ml), and possibly, therefore, their higher allergic reactivity.

Incidence of atopic disease in a tropical environment: partial independence from intestinal helminthiasis.

The reported incidence of atopic disease in the tropical environment, albeit somewhat controversial, has often been very low. This has been postulated to be due to an inhibitory influence of intestinal helminthiasis, although the predominantly rural nature of the populations studied might also be an important factor to consider. We evaluated two tropical groups in Venezuela that were basically comparable, both being highly parasitized but one of which was urban and the other rural. The apparent incidence of allergic conditions in the urban group was, in fact, comparable to that in temperate countries, whereas that of the rural subjects was markedly lower. A similar difference was found in skin test positivity to common inhalant allergens, although reactivity to Ascaris extract was comparably high between the two groups, and total serum IgE and eosinophil levels were uniformly elevated. Our results suggest that the incidence of atopic disease in the topical environment may depend not only on the intensity of helminthiasis suffered but also on factors related to the urban-rural situation.

Diagnosis of atopic conditions in the tropics.

Controversy surrounds studies of the incidence and clinical importance of atopic disease in tropical populations. This could be due in part to the methods of evaluation employed. The value of some of the tests commonly used in the diagnosis of atopic disease was therefore examined in a tropical situation. Extracts of environmental allergens are usually obtained from suppliers located in more temperate regions of the world, and skin tests, the radio-allergosorbant test (RAST) and RAST-inhibition demonstrate that these can lack important tropical allergens. In addition, although some local extracts are used in clinical practice, these have great variability in their protein content, allergenicity and toxicity. In the tropical environment serum IgE levels can have a greater relation to intestinal helminthic infestation than to atopic disease, even after anti-parasitic treatment, and thus the definition of "normal" IgE values must take into account the socio-economic status of the groups examined. The helminth-induced elevation of total serum IgE levels can also cause false-positive RAST results.