**2.9 IgE/IgG to food antigens**

It has been shown that EoE patients' serum exhibited various IgE against food antigens. For instance, Roy-Ghanta et al. found that 82% of 23 patients with biopsyproven EoE exhibited serum IgE targeting one or more food-associated allergens.

*Autoimmune Diseases of the GI Tract Part II: Emergence of Diagnostic Tools and Treatments DOI: http://dx.doi.org/10.5772/intechopen.106185*

Most common food allergens were onion, wheat, carrot, and tomato [62, 63]. Moreover, Erwin et al. have also concluded that EoE-sensitized patients have higher IgE titers in comparison to nonsensitized patients (median, 150 vs. 13 IU/mL; P < .001) [64]. It is also common for EoE patients to have IgE targeting some milk proteins. For example, using ImmunoCAP assays for specific milk allergens, Erwin et al. have detected positive IgE antibodies in 31 out of 34 EoE patients. He then detected a strong correlation between IgE antibodies targeting Bos d 4 (α-lactalbumin) and Bos d 5 (β-lactoglobulin) and milk extract (R = 0.89 and R = 0.76 respectively; p < 0.001) [65]. In another example, Schuyler et al. also confirm the prevalence of antibodies against milk proteins in EoE patients. He found that 79% of 67 children diagnosed with EoE had cow milk (CM) sensitization (sIgE ≥0.10 IU/mL) compared with unselected controls, where only 22% of 101 had CM sensitization. When comparing specific IgG4 and total IgG4, both were significantly detected in EoE patients in comparison to unselected controls (p < 0.001 vs. p < 0.01, respectively). Just like Erwin et al., Schuyler et al. also found significantly high titer of antibodies against alpha-lactalbumin; however, the antibody was sIgG4, when compared to control (p < 0.001). He also detected another targeted protein in milk which was caseins (p < 0.001) [66]. Clayton also reports the presence of IgG4 targeting food in EoE patient's serum [67].

### **2.10 Aeroallergen-specific IgE**

There can be a difference in aeroallergen-specific IgE serum levels between age groups in EoE patients. For instance, Erwin et al. have noticed that children have higher aeroallergen-specific IgE serum levels than adults. Regarding specificities, Erwin et al. have shown that prevalence of sensitization to one or more aeroallergen specificities was higher than that in children (93% vs. 65%), while the sensitization to each individual aeroallergens ranged from 12 to 61% [65].

### **2.11 Circulating antimyenteric autoantibodies (CAA)**

CAA are circulating antibodies that target the myenteric neurons located in the GI tract. Several studies have associated those autoantibodies with the pathogenesis of achalasia disease. For instance, Storch et al. have detected IgG antibodies directed at Auerbach's plexus, also named myenteric plexus, in patients with achalasia with varying duration and stages of diseases (specificity 93%, sensitivity 64%, p < 0.0001) [68]. Furthermore, Verne et al. also detected them in 7 out of 18 achalasia patients. Those autoantibodies were found to stain most of the neurons found within plexi in the intestinal and esophageal sections, even nitric oxide synthase positive and negative neurons. While none of the controls exhibited neuronal staining [69]. Moreover, Ruiz-de-León et al. also confirmed CAA association with achalasia, as he found CAA in 54.3% of patients with achalasia and only 7.5% of healthy individuals (P < 0.001) [70]. When examining nuclear or cytoplasmic fluorescence patterns, Kallel-Sellami et al. found significantly high titers of CAA in patients with achalasia, in comparison to healthy controls (33% vs. 12%, P = 0.03 and 48% vs. 23%, P = 0.001 respectively) [71]. On the other hand, Kraichely et al. did not detect any specific myenteric neuronal antibody in all the 70 patients with primary achalasia he examined. Instead, they found significantly high levels of GAD65 autoantibody in patients with achalasia, which is an autoantibody found in other autoimmune diseases such as type 1 diabetes mellitus (P < 0.0001) [72].
