Figure 3. Inflammatory Micro-Environments Characterizing CD.

There is considerable evidence that Th1 and Th17 responses are in an uneasy state of co-existence (See Figure 2). In this figure the concept is put-forward that such co-existence is minimized by the fact that Crohn’s inflammation consists of innumerable micro-environments, each exhibiting a progression of inflammatory patterns. In the initial and most intense phase of the inflammation, Th1 responses predominate; at this point, production of IL-23 in a nascent Th17 response inhibits Treg generation and feeds the inflammation. In a later phase a mixed T cell response prevails in which the Th1 response is still predominant but is now moderated by a Th17 response producing both IL-17 (which inhibits IFN-γ T cells) and IL-22.