# Characterization of Th2 Serum Immune Response in Acute Appendicitis

## TL;DR

This study found that while a Th2 immune response occurs locally in phlegmonous appendicitis, it is not reflected in blood serum levels of immune cells or cytokines.

## Contribution

The study reveals that local Th2 immune activity in appendicitis does not translate to detectable serum markers.

## Key findings

- Phlegmonous appendicitis showed higher central memory CD4 T cells and Th1 cells in blood, but not Th2 cells.
- Local Th2 immune response in appendicitis is not mirrored by serum levels of IgE, IL-5, or IL-13.
- Serum basophils were elevated in phlegmonous appendicitis, while eosinophils were higher in the control group.

## Abstract

Acute Appendicitis (AA) is the commonest abdominal digestive surgical emergency, but its etiology is not clarified. Based on histologic observations, an allergic cause has been proposed. In a type I hypersensitivity allergic reaction, there is a Th2 immune response characterized by Th2 cells, eosinophils, basophils, IgE, IL-4, IL-5, and IL-13 serum elevation. Recent studies showed a local appendicular endoluminal and parietal Th2 immune response in acute phlegmonous appendicitis. We performed a prospective single-center study where we evaluated the Th2 blood immune response in 38 patients with acute phlegmonous appendicitis, 27 patients with acute gangrenous appendicitis, and 18 patients with the clinical picture of AA, who underwent appendectomy but had negative histology for AA (negative appendectomy group). Higher levels of basophils were found in phlegmonous appendicitis (p = 0.03), and higher levels of eosinophils were found in the control group (p = 0.003). Effector memory CD4 T cells re-expressing CD45RA were higher in gangrenous (p = 0.020) and central memory CD4 T cells in phlegmonous appendicitis (p = 0.004). The number of Th2 circulating cells was higher in gangrenous appendicitis (p = 0.037), while Th1 circulating cells were higher in phlegmonous appendicitis (p = 0.028). IL-4 blood concentrations were elevated in acute gangrenous appendicitis (p = 0.029). No significant differences were found in the levels of IgE, IL-5, or IL-13 in any of the groups. Thus, a Th2 response was not detected in patients’ serum with phlegmonous appendicitis. Serum levels of IgE, IL-5, and IL-13 were not different among patients with acute phlegmonous appendicitis, acute gangrenous appendicitis, and the negative appendectomy group. These findings are in contrast to our previous work in which we evaluated the Th2 response at the local level, at the appendicular luminal aspect and appendicular wall, in phlegmonous appendicitis and control groups, and we unequivocally showed a Th2 response in phlegmonous appendicitis. Thus, in patients with phlegmonous appendicitis, the local Th2 response is not reflected in the serum levels of immune cells and cytokines.