<i>Background:</i> Genetic studies of atopy rely upon evidence of abnormal IgE production, usually elevated total IgE or skin prick test (SPT) reactions. However, these measures may change with subject age. <i>Methods:</i> We screened 1,099 members of atopic families (aged 6–87 years) by serum total IgE and SPT for 14 allergens. For those SPT negative, we screened for Amb a 1- and Der p 1-specific IgE. Der p 1 IgE-Der p 1 allergen binding affinities were done on randomly selected subjects. <i>Results:</i> There were significantly fewer atopics ≤10 years old (69.1%) compared to those >10 years old (75.8%) based upon any SPT-positive result. Children ≤10 years had fewer SPT-positive reactions and smaller SPT wheal reaction areas. Yet, mean total IgE values were comparable to those of the older group. Screens for specific IgE showed no differences in proportions of atopics (≤10 years old = 83.1% and >10 years old = 82.3%). Among those SPT-positive for house dust mite extract, there was a positive correlation between Der p 1 binding affinity and the wheal area of the house dust mite extract. There was a positive correlation between the number of SPT-positive reactions and total IgE for both age groups. However, there was only a significant relationship between SPT-positive wheal area and total IgE for those >10 years old and no apparent relationship between wheal area and total IgE for those ≤10 years old. <i>Conclusion:</i> These results suggest that atopy-specific physiological mechanisms, primarily those involving allergen-IgE binding, change during the earliest years of life.
We evaluated atopy-associated parameters in 1,099 people (aged 6-84 years) from families with history for atopy. All were tested for serum total immunoglobulin E (IgE) and allergen sensitivity by skin prick test. Specific IgE tests were done in randomly selected families. There was a decline with age in serum total IgE values, and relative atopy "incidence rates" were slightly lower among those older than 60 years. However, there was no change with age in sensitivity or severity of atopy. Among those sensitized to ragweed (Ambrosia artemisilfolia), there was no age-associated change in IgE levels specific to Amb a 1, a major allergen extracted from ragweed, and no change in the binding affinity of IgE for the Amb a 1 allergen. Among families with atopic histories, the underlying atopic mechanisms are particularly robust, and the atopic propensity remains into advanced age. In addition, established atopic responses may be focused in an immune system compartment either independent of or minimally influenced by T-cell activity.
Background Atopy is an aberrant immune response involving allergen‐specific IgE production, though serum IgE concentration is not an entirely reliable diagnostic tool, particularly for epidemiological and genetic studies. There is no clear correlation between IgE and other indicators of atopy such as skin prick tests (SPT)s, and physiological associations are difficult to justify in cases with detectable IgE but negative SPT results. Objective IgE reflects the number of molecules available to produce an atopic response, but the degree of the response is determined by the binding strength (affinity) between receptor‐bound IgE and the allergen. We sought to determine if there was an association between binding affinity and SPT results in people with histories of atopy. Methods Standard SPTs (whole allergen extracts) were administered to people with histories of sensitivities to ragweed and house dust mite. The concentrations and affinities of serum allergen‐specific IgEs were determined using the purified allergens Amb a 1 and Der p 1. Results There was a positive correlation between weal area and allergen‐specific IgE among SPT‐positive donors. However, for those individuals with detectable amounts of allergen‐specific IgE, there was considerable overlap of IgE values between SPT‐positive and ‐negative groups. Among sensitized donors, IgE–allergen interactions were characterized by two or three specific reactions of very high affinity ( K A range 10 8 −10 11 M). Negative SPT reactions were associated with lowered IgE binding affinities to major allergens. This delimited two groups with atopic disorders: specific IgE( + )/SPT( + ) and specific IgE( + )/SPT( – ). Conclusion The product of antibody affinity and concentration, which we define as antibody capacity (CAP = K A × IgE), is more informative with regard to describing allergen sensitivity than antibody concentration alone. Antibody binding capacity provides physiological evidence of atopy in some subjects who do not test positively by common methods and suggests an affinity threshold to produce a positive SPT reaction.
Breast cancers often have increased mitogen-activated protein kinase (MAPK) activity; this pathway influences breast cancer cell growth in part by targeting steroid hormone receptors. Activation of p42 and p44 MAPKs increases progesterone receptor (PR) transcriptional activity in the presence of progestins, and triggers their rapid down-regulation by the ubiquitin-proteasome pathway. In turn, progestins increase the expression of type I growth factor receptor tyrosine kinases that feed into MAPK activation. Most recently, progestins have been shown to activate the p42/p44 MAPK module in a progesterone receptor (PR) dependent manner, but independently of their function as transcription factors. Indeed, mechanisms of bi-directional cross-talk between these two pathways are becoming well-documented. In this reveiw we provide an overview of the primary ways in which steroid hormone receptor and growth factor cross-talk occurs, using examples from our work and others with human PR as a model receptor. We highlight the regulation of PR by phosphorylation and the role of intracellular protein kinases as key mediators of PR action. Cross-talk between growth factor and PR-mediated signaling events is an important means by which growth regulatory genes may be coordinately regulated, and may contribute to the growth and development of hormonally responsive normal breast tissue and to breast cancer progression.
Human progesterone receptors (PR) are phosphorylated by cyclin-dependent protein kinase 2 (CDK2) at multiple sites, including Ser400. Herein, we have addressed the significance of phosphorylation of this residue. PR phospho-Ser400-specific antibodies revealed regulated phosphorylation of Ser400 in response to progestins and mitogens, and this correlated with increased CDK2 levels and activity. Expression of cyclin E elevated CDK2 activity and downregulated PR independently of ligand. Similarly, overexpression of activated mutant CDK2 increased PR transcriptional activity in the absence and presence of progestin. Mutation of PR Ser400 to alanine (S400A) blocked CDK2-induced PR activity in the absence, but not in the presence, of progestin. PR was unresponsive to activated CDK2 in breast cancer cells with elevated p27, and RNA interference knock-down of p27 partially restored CDK2-induced ligand-independent PR activation. Similarly, in p27(-/-) mouse embryonic fibroblasts, elevated CDK2 activity increased wild-type (wt) but not S400A PR transcriptional activity in the absence of progestin. CDK2 induced nuclear localization of unliganded wt but not S400A PR; liganded S400A PR exhibited delayed nuclear accumulation. These studies demonstrate that CDK2 regulates PR in the absence of progestins via phosphorylation of Ser400, thus revealing a novel mechanism for upregulated PR transcriptional activity in human breast cancer cells expressing altered cell cycle regulatory molecules.
