It is well established that malnutrition affects the immune response and increases the susceptibility to parasitic infection. In the present study we evaluated some aspects of the cellular and cytokine network that regulate the IgE responses, which are important components of host defence mechanisms against helminthic parasites in children infected with the intestinal helminth Ascaris lumbricoides, and with differing degrees of malnutrition. We found a defective T cell response in malnourished children, as indicated by diminished levels of circulating total (CD3+), helper (CD4+), IL-2-receptor-bearing (CD4+CD25+) and memory helper T cell responses (CD4+CD45RO+) in keeping with the decreased specific IgE levels against Ascaris lumbricoides. In contrast, the proportions of total B cells (CD20+), and those bearing the low-affinity IgE receptor (CD23+) were increased in the moderated malnourished children. Moreover, serum IL-4 levels and total IgE were also increased in these children. We suggest that malnutrition can cause an imbalance in T cell subpopulations that may lead to a defective T cell maturation and a decreased specific anti-Ascaris IgE response thus increasing the susceptibility to such infections. The high levels of total IgE observed may be related to a non-specific stimulation of the proliferation of activated B cells, probably caused by helminthic parasites and other infectious agents that are frequent in malnourished children.
We evaluated helminthic infection and anthropometric indicators of nutritional status in a group of school-age children from a slum area of Caracas, Venezuela. The proportions of children at or below the 10th percentiles for height/age and weight/age were significantly higher in those presenting helminthiasis than in those uninfected. Although this could partially reflect a codependence of both helminthic infection and undernutrition or poverty, when the children were administered regular anthelmintic treatment for a year their anthropometric values improved significantly. When they were re-evaluated 8 months after the end of anthelmintic administration, the degree of reinfection by the most common helminth, Ascaris lumbricoides, was significantly higher in the growth-retarded children. These results confirm the relationship between helminthic infection and decreased growth rates in underprivileged populations, and indicate that children at nutritional risk are more susceptible to such infections, even after a prolonged parasite-free period.
Summary
The biological properties of the homocytotropic antibody (HCA) of the marsupial Setonix brachyurus (the quokka) were closely comparable to those of eutherian (placental species) IgE. However, the quokka HCA was indistinguishable from the IgG1 class. Agar gel electrophoresis, Sephadex G‐200 chromatography and sequential elution from DEAE‐cellulose and CM‐cellulose did not separate the passive cutaneous anaphylactic (PCA) and IgG1 passive haemagglutination (HA) activities in quokka antisera. No antigenic differences between the IgG1 HA antibody and the HCA were detected. In addition to quokka IgG1, tissue‐fixing IgG has been demonstrated in eutherian and avian species and thus it is suggested that the extant IgG and IgE classes evolved from a primitive cytotropic γ chain.
Summary
Immunization of the marsupial Setonix brachyurus (the quokka) with ovalbumin and the dinitrophenyl hapten, in conjunction with either alumina gel or Freund's complete adjuvant, induced the synthesis of low levels of homocytotropic antibody (HCA). This antibody elicited passive cutaneous anaphylactic (PCA) reactions of maximal intensity after latent periods of 48 to 72 hours and persisted at passively sensitized skin sites for at least 10 days. The HCA activity in quokka antisera was labile both to heating at 56° and to reduction with 2‐mercaptoethanol. The biological characteristics of the quokka HCA were therefore closely comparable to those of the reaginic (IgE) antibodies of eutherian (placental) species. Because of this similarity, it is suggested that the immediate hypersensitivity system was developed prior to the evolutionary divergence of these two groups.
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