David G. Marsh

Sib-pair analysis of 170 individuals from 11 Amish families revealed evidence for linkage of five markers in chromosome 5q31.1 with a gene controlling total serum immunoglobulin E (IgE) concentration. No linkage was found between these markers and specific IgE antibody concentrations. Analysis of total IgE within a subset of 128 IgE antibody-negative sib pairs confirmed evidence for linkage to 5q31.1, especially to the interleukin-4 gene (IL4). A combination of segregation and maximum likelihood analyses provided further evidence for this linkage. These analyses suggest that IL4 or a nearby gene in 5q31.1 regulates IgE production in a nonantigen-specific (noncognate) fashion.

Atopic asthma is characterized by inflammatory responses of the airway and is associated with up-regulation of Th2 cytokines, notably IL-4 and IL-5. A recently described human cytokine, IL-13, is a potent in vitro modulator of various cell types, including monocytes, B cells, and endothelial cells. Similar to IL-4, it is also involved in the induction of IgE synthesis. However, the in vivo expression and function of IL-13 and its relation to disease remain to be defined. Using a segmental allergen challenge model, we have examined the in vivo expression of IL-13 in the bronchoalveolar lavage (BAL) cells of atopic patients. We found a significant enhancement of both IL-13 transcripts and secreted proteins in the allergen-challenged BAL compared with the saline-challenged control sites of asthmatic and rhinitic patients. In contrast, the expression of IL-13 transcripts was not detected in the BAL of two normal subjects challenged with the same dose of ragweed allergen. The cellular source of IL-13 mRNA was identified in the mononuclear cell fraction of the allergen-challenged BAL. The allergen-induced quantitative differences in the level of transcripts were confirmed by competitive PCR assays. These results suggest that the significant increase in IL-13 in the allergen-challenged BAL is primarily from the mononuclear cells and is involved in the regulation of allergen-induced late phase inflammatory responses.

STUDIES of atopic allergy ("allergy") have provided new insight in defining the epidemiologic and genetic basis for the human immune response.1 , 2 Allergy is characterized by the development of antibody responses of a unique immunoglobulin — IgE3 — after exposure to inhaled, ingested, or injected antigens (usually termed "allergens"). Under conditions of natural exposure to extremely low doses (usually less than 1 μg per year),4 atopic persons have IgE-antibody responses toward an array of environmental allergens present in pollens, fungal spores, animal danders, and similar substances. Synthesis of IgE is favored by natural immunization through inhalation, since antigens come directly into . . .

This is a revision of the allergen nomenclature system which was proposed in 1986. The nomenclature is for allergens which induce IgE-mediated allergy in humans. A table of allergens with known partial or complete sequences as of December 1993 is given.

Ultra-pure short ragweed pollen allergen Ra5 (5,000 mol wt) was used to investigate the relationship between human leukocyte antigen (HLA) type and IgE and IgG antibody (Ab) responses to Ra5 in two groups of Caucasian subjects, totaling 447 people. Using highly sensitive radioimmunoassay procedures to measure serum IgE and IgG Ab, qualitative responses to Ra5 in both groups were found to be strongly associated with HLA-Dw2 (P less than 0.0001). For example, 95% of 38 people with IgE Ab vs. 22% of 139 ragweed-allergic persons having no detectable IgE Ab to Ra5 were Dw2+. Quantitative log [IgE Ab] and log[IgG Ab] responses to Ra5 were highly correlated with Dw2 (P = 10(-5) to 10(-14)) in four separate multiple regression analyses, examining the relationship between HLA type (and other variables) and Ab levels in the two study groups. Further studies showed that the primary association of Ra5 response was with Dw2 rather than DR2 and that various combinations of A3, B7, and Dw2 were less strongly associated than Dw2 alone.