Written By Dr. Wayne Sodano,
Director of Clinical Support & Education For Evexia Diagnostics
The term ‘food sensitivity’ relates to a purely immune system-mediated response involving various classes of food-specific immunoglobulin molecules that can form food immune complexes.1 “These complexes can stimulate the complement cascade and localized inflammation.”2 “Food is an ideal source of antigens to trigger the enteric immune system as it provides abundant antigens to susceptible location, often presenting the same food proteins on a daily basis.”3 Additionally, undigested food proteins provide ‘feed’ for intestinal dysbiosis that can stimulate hypersensitivity of the mucosal associated lymphoid tissue. IgG (IgE) form against food proteins that cross the enterocyte barrier.4
There are four classes of IgG (IgG1 - IgG4). Their attributes include:
IgG1 and IgG3 can activate complement. “Complement activation is a multistep cascade which leads to the formation of a membrane attack complex that can kill a target cell or bacteria.”5 The complement system consists of a group of serum proteins that activates inflammation, destroys cells and participates in opsonization. Complement can be activated by a number of different foreign substances. The complement system responds in a sequential manner, producing a cascade of reactions. Most of the proteins are normally inactive, but in response to the recognition of molecular antigens (e.g. bacteria, foods, etc.) they become sequentially activated. The major protein components are C1 through C9. The complement cascade can be activated by the classical pathway, alternative pathway and lectin pathway. “Complement has been considered mainly in the systemic compartment, and serum levels of most components of the complement system, including C3, C4 and MBL (associated serine protease) are produced by the hepatocyte. Other tissues also contain cells capable of complement production: for example, endothelial and epithelial cells are also able to secrete various complement components.”6
The FIT test (Food Inflammation Test) improves sensitivity to testing for a reaction to food by measuring both IgG (1 though 4) plus complement C3d bound to immune complexes, which results in a test that generates two signals; one for the IgG plus one signal for the IC-C3d (immune-complex C3d). This type of testing vastly improves the sensitivity of food testing resulting in improved clinical outcomes.
The important benefits of the FIT test include:
When to consider ordering the FIT Test:
1 Lord RS, Brailey JA. Laboratory Evaluations for Integrative and Functional Medicine. Canada; Riverstone Group. 2008. 434.
3 Lewis CA. Enteroimmunology. Florida; Psy Press. 2-14. P. 172.
5 Ibid. p. 175
6 Lubbers R, van Essen MF, van Kooten C, Trouw LA. Production of complement components by cells of the immune system. Clinical and Experimental Immunology. 2017; 188:183-194.