Delayed clinical and ex vivo response to mammalian meat in patients with IgE to galactose-alpha-1,3-galactose.

BACKGROUND: In 2009, we reported a novel form of delayed anaphylaxis to red meat related to serum IgE antibodies to the oligosaccharide galactose-alpha-1,3-galactose (alpha-gal). Although patients were remarkably consistent in their description of a 3- to 6-hour delay between eating mammalian meat and the appearance of symptoms, this delay has not been demonstrated under observed studies. OBJECTIVES: We sought to formally document the time course of clinical symptoms after the ingestion of mammalian meat in subjects with IgE to alpha-gal and to monitor ex vivo for the appearance of markers of an allergic reaction. METHODS: Open food challenges were performed with mammalian meat in 12 subjects with a history of severe urticarial reactions 3 to 6 hours after eating beef, pork, or lamb, as well as in 13 control subjects. Blood samples were taken hourly during each challenge. RESULTS: Ten of 12 subjects with IgE to alpha-gal had clinical evidence of a reaction during the food challenge (vs none of the control subjects, P < .001). The reactions occurred 3 to 7 hours after the initial ingestion of mammalian meat and ranged from urticaria to anaphylaxis. Tryptase levels were positive in 3 challenges. Basophil activation, as measured by increased expression of CD63, correlated with the appearance of clinical symptoms. CONCLUSION: The results presented provide clear evidence of an IgE-mediated food allergy that occurs several hours after ingestion of the inciting allergen. Moreover, here we report that in vivo basophil activation during a food challenge occurs in the same time frame as clinical symptoms and likely reflects the appearance of the antigen in the bloodstream.

Role of direct RhoA-phospholipase D1 interaction in mediating adenosine-induced protection from cardiac ischemia.

Activation of adenosine A1 or A3 receptors protects heart cells from ischemia-induced injury. The A3 receptor signals via RhoA and phospholipase D (PLD) to induce cardioprotection. The objective of the study was to investigate how RhoA activates PLD to achieve the anti-ischemic effect of adenosine A3 receptors. In an established cardiac myocyte model of preconditioning using the cultured chick embryo heart cells, overexpression of the RhoA-noninteracting PLD1 mutant I870R selectively blocked the A3 agonist (Cl-IBMECA, 10 nM)-induced cardioprotection. I870R caused a significantly higher percentage of cardiac cells killed in A3 agonist-treated than in A1 agonist (CCPA, 10 nM)-treated myocytes (ANOVA and posttest comparison, P<0.01). Consistent with its inhibitory effect on the PLD activity, I870R attenuated the Cl-IBMECA-mediated PLD activation. Cl-IBMECA caused a 41 +/- 15% increase in PLD activity in mock-transfected myocytes (P<0.01, paired t test) while having only a slight stimulatory effect on the PLD activity in I870R-transfected cells. To further test the anti-ischemic role of a direct RhoA-PLD1 interaction, atrial cardiac myocytes were rendered null for native adenosine receptors by treatment with irreversible A1 antagonist m-DITC-XAC and were selectively transfected with the human adenosine A1 or A3 receptor cDNA individually or they were cotransfected with cDNAs encoding either receptor plus I870R. I870R preferentially inhibited the human A3 receptor-mediated protection from ischemia. The RhoA-noninteracting PLD1 mutant caused a significantly higher percentage of cardiac cells killed in myocytes cotransfected with the human A3 receptor than in those cells expressing the human A1 receptor (ANOVA and posttest comparison, P<0.01). The present data provided the first demonstration of a novel physiological role for the direct RhoA-PLD1 interaction, that of potent protection from cardiac ischemia. The study further supported the concept that a divergent signaling mechanism mediates the anti-ischemic effect of adenosine A1 and A3 receptors.