**1. Introduction**

Inflammatory bowel disease (IBD) mainly includes ulcerative colitis (UC) and Crohn's disease (CD). Both conditions are characterized by chronic inflammation of the gastrointestinal tract, with alternating periods of relapse and remission. Both forms of IBD involve an uncontrolled inflammatory process in the intestines, leading to worsening quality of life and requiring long-term medical and/or surgical intervention [1].

The pathomechanism of IBD is still not well explain, but evidence suggests that it results from perturbation of the homeostasis between the intestinal microbiota and the mucosal immune system, with the involvement of both genetic and environmental factors [2].

Ulcerative colitis is a chronic inflammatory disease, which mainly affects the large intestine. Typical clinical symptoms of UC are diarrhea, rectal bleeding, and abdominal pain. Nonspecific symptoms include fever, appetite loss, and weight loss. The disease significantly affects the patient's quality of life due to its repeated remissions and relapses [3].

UC is characterized by recurring episodes of inflammation limited to the mucosal layer of the colon and practically invariably involves the rectum and may extend in a proximal and continuous fashion to involve other portions of the colon. Endoscopic features of inflammation include loss of vascular markings, granularity and friability of the mucosa, and erosions. In the setting of severe inflammation is observed deep ulcerations and spontaneous bleeding [4] (**Figure 1**). CD is described by transmural rather than superficial mucosal inflammation and by skip lesions rather than continuous disease [5].

In Crohn's disease, inflammatory changes may occur in all parts of the gastrointestinal tract, from the oral cavity to the rectum, but are usually localized in the terminal segment of the small intestine, that is, the ileum. Inflammatory changes are discontinuous and affect the entire thickness of the intestinal wall. The most common symptoms of CD are abdominal pain, fever, weight loss, and diarrhea [6].

The commonly used instrument for evaluating the disease severity of CD is Crohn's Disease Activity Indicator (CDAI; remission <150 score, severe disease >450 score). Whereas the Mayo score (0—normal, 3—severe disease) is used to assess the severity of ulcerative colitis [7].

The optimal goal of management in IBD is a durable period of steroid-free remission and the induction and subsequent maintenance of mucosal healing [4]. Mucosal healing is predominantly defined by endoscopic assessment of intestinal inflammation and is referred to as the absence of mucosal ulcerations in CD, while in UC, an international consensus defined it as the absence of friability, blood, erosions, and ulcers of the gut mucosa. However, these indices allow to determine improvements of endoscopic lesions, even when the rather rigid endpoint of mucosal healing, and thereby the total disappearance of all mucosal ulcerations is not met [8] (**Figure 2**).

Many genes, which may be linked to IBD, are believed to be associated with microbiological defense mechanisms involving the epithelial barrier and innate, adaptive immune systems [9].

**Figure 1.** *Endoscopic images of ulcerative colitis according to the Mayo score (Grade 3—severe disease). (Source: Own study.)*

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**genes in IBD**

**Figure 2.**

Cardinal Wyszynski in Lublin.

*Single-Nucleotide Polymorphisms in Inflammatory Bowel Disease*

In the result of large cohort genome-wide association studies (GWAS) of cases

Among the genetic factors involved, there are several single-nucleotide polymorphisms (SNP) associated with the susceptibility to IBD progression. Many of these mutations regulate immune responses with several being enriched in immune

**2. Single-nucleotide polymorphisms in innate and adaptive immunity** 

The latest research on genetics and immunology has confirmed that the innate immune system is of great importance in inducing intestinal inflammation [13], and the publication of Dudzińska et al. [14], "Single nucleotide polymorphisms in selected genes in inflammatory bowel disease," is dedicated to this issue. This paper attempts to demonstrate polymorphisms *NOD2/CARD15* (*nucleotide-binding oligomerization domain containing 2/caspase recruitment domain family number 15*) and the *DLG5* gene (*discs large homolog 5*) in patients with IBD hospitalized at the Department of Gastroenterology, Regional Specialist Hospital, SPZOZ im. Stefan

*NOD2/CARD15* is located on chromosome 16q12.1 and was the first diseasesusceptibility gene discovered for CD. *NOD2/CARD15* is a pattern-recognition receptor that is involved in the homeostasis of intestinal immunity [15].

*CARD15/NOD2* plays an important role in immune function. In response to bacterial infection, *CARD15/NOD2* acts as an intracellular bacterial receptor and activates the kappa B nuclear factor (NF-κB), particularly after recognizing the

and controls, over 200 IBD susceptibility loci have now been reported [10]. GWAS research was aimed at searching the SNPs that are over-represented in IBD patients when compared with healthy controls. SNPs that occurred more frequently in IBD patients are thus called disease-associated variants [11].

*Endoscopic assessment of the large intestine was observed by mucosal bridging and pseudopolyps, which confirms regeneration of the mucosa in the course of remission of ulcerative colitis. (Source: Own study.)*

cells, in particular CD4+ T cells and dendritic cells [12].

bacterial wall component muramyl dipeptide (MDP) [16].

*DOI: http://dx.doi.org/10.5772/intechopen.92051*

#### **Figure 2.**

*The Recent Topics in Genetic Polymorphisms*

lesions rather than continuous disease [5].

severity of ulcerative colitis [7].

not met [8] (**Figure 2**).

adaptive immune systems [9].

diarrhea [6].

UC is characterized by recurring episodes of inflammation limited to the mucosal layer of the colon and practically invariably involves the rectum and may extend in a proximal and continuous fashion to involve other portions of the colon. Endoscopic features of inflammation include loss of vascular markings, granularity and friability of the mucosa, and erosions. In the setting of severe inflammation is observed deep ulcerations and spontaneous bleeding [4] (**Figure 1**). CD is described by transmural rather than superficial mucosal inflammation and by skip

In Crohn's disease, inflammatory changes may occur in all parts of the gastrointestinal tract, from the oral cavity to the rectum, but are usually localized in the terminal segment of the small intestine, that is, the ileum. Inflammatory changes are discontinuous and affect the entire thickness of the intestinal wall. The most common symptoms of CD are abdominal pain, fever, weight loss, and

The commonly used instrument for evaluating the disease severity of CD is Crohn's Disease Activity Indicator (CDAI; remission <150 score, severe disease >450 score). Whereas the Mayo score (0—normal, 3—severe disease) is used to assess the

The optimal goal of management in IBD is a durable period of steroid-free remission and the induction and subsequent maintenance of mucosal healing [4]. Mucosal healing is predominantly defined by endoscopic assessment of intestinal inflammation and is referred to as the absence of mucosal ulcerations in CD, while in UC, an international consensus defined it as the absence of friability, blood, erosions, and ulcers of the gut mucosa. However, these indices allow to determine improvements of endoscopic lesions, even when the rather rigid endpoint of mucosal healing, and thereby the total disappearance of all mucosal ulcerations is

Many genes, which may be linked to IBD, are believed to be associated with microbiological defense mechanisms involving the epithelial barrier and innate,

*Endoscopic images of ulcerative colitis according to the Mayo score (Grade 3—severe disease). (Source: Own* 

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**Figure 1.**

*study.)*

*Endoscopic assessment of the large intestine was observed by mucosal bridging and pseudopolyps, which confirms regeneration of the mucosa in the course of remission of ulcerative colitis. (Source: Own study.)*

In the result of large cohort genome-wide association studies (GWAS) of cases and controls, over 200 IBD susceptibility loci have now been reported [10].

GWAS research was aimed at searching the SNPs that are over-represented in IBD patients when compared with healthy controls. SNPs that occurred more frequently in IBD patients are thus called disease-associated variants [11].

Among the genetic factors involved, there are several single-nucleotide polymorphisms (SNP) associated with the susceptibility to IBD progression. Many of these mutations regulate immune responses with several being enriched in immune cells, in particular CD4+ T cells and dendritic cells [12].
