*The Role of Apoptosis in Autoimmune Destruction of Pancreatic b-Cells DOI: http://dx.doi.org/10.5772/intechopen.108290*

We examined 63 patients with a reliably established diagnosis of T1DM and 15 individuals with a high risk of developing T1DM. The control group (Group I) consisted of 30 healthy individuals, comparable in sex and age to patients with T1DM. The distribution of patients into groups was carried out depending on the phase of compensation and the duration of the course of the disease. Group II (decompensated T1DM) consisted of 17 patients with newly diagnosed T1DM (group IIa) and 19 patients with an average duration of T1DM of 15.3 ± 5.1 years (group IIb). Group III (the state of compensation for T1DM) included 13 patients with a disease duration of up to 1 year (group IIIa) and 14 patients with an average duration of T1DM of 15.1 ± 5.4 years (group IIIb). Group IV consisted of 15 persons with a high risk of developing T1DM, who are immediate family members of the examined patients with T1DM. Additional selection criteria for the risk group were an increased titer (>1/20) of autoantibodies to cytoplasmic antigens of islet cells (Islet Cell Autoantibodies) in serum and impaired glucose tolerance.

*Immunophenotyping of peripheral blood mononuclear cells* was performed by flow cytometry using the following monoclonal antibodies manufactured by "Immunotech" (Beckman Coulter Corporation, USA): anti-CD3 conjugated with FITC (Fluorescein Isothiocyanate), anti-CD4-FITC, anti-CD8-FITC, anti- CD16- FITC, anti-CD20-FITC, anti-CD25-FITC, anti-HLA-DR-FITC, anti-CD95-FITC and their isotype controls.

*To assess apoptotic processes in individual subpopulations of T lymphocytes*, the level of surface expression of the Fas receptor was determined using a double fluorescent label—FITC (Fluorescein Isothiocyanate) and PE (Phycoerythrin). The study was performed using the following combinations of antibodies: anti-CD3-FITC/ anti-CD95-PE, anti-CD4-FITC/anti-CD95-PE and anti-CD8-FITC/anti-CD95-PE. Cytometric analysis of lymphocytes was performed on an EPICS XL flow cytometer (Beckman Coulter Corporation, USA).

*Determination of soluble forms of the Fas receptor (sFas) and Fas ligand (sFasL)* in blood serum was carried out by indirect enzyme-linked immunosorbent assay (ELISA) using the "Human sFas Ligand ELISA" test systems (Bender MedSystems, Austria) and "Human Fas ELISA" test systems (BD Biosciences, USA).

The data we obtained are presented in **Table 1**. The maximum increase in the relative and absolute content of T-lymphocytes expressing the Fas receptor was found during decompensation of T1DM, which is explained by the influence of hyperglycemia, a secondary immune response to the so-called "late apoptotic" b-cells due to their inefficient phagocytic clearance and is consistent with the data literature [2]. It has been established that hyperglycemia increases the sensitivity of T cells to Fasmediated apoptosis due to increased expression of the Fas receptor on their surface, and also induces p53-mediated apoptosis of target cells with the participation of effector caspase-3 [35, 36].

The maximum increase in the relative and absolute amount of CD95+ cells and the number of T-lymphocytes expressing the Fas receptor (Fas) was found in T1DM decompensation, regardless of the duration of the disease (groups IIa and IIb). These data indicate that in T1DM, an increase in the readiness of immunocompetent cells for apoptosis does not depend on the duration of the disease, but is clearly associated with the decompensation of carbohydrate metabolism and the level of glycemia.

**Figure 1** shows a comparative assessment of the level of surface expression of the Fas receptor (CD95+) in individual subpopulations of T-lymphocytes in T1DM patients in a state of carbohydrate metabolism decompensation and in the control group.


 *Notes: (1) I—control group (healthy persons); Ia group—the state of decompensation, newly diagnosed T1DM; IIb group—he state of decompensation, the average duration of the T1DM is 15.3 ± 5.1 years; IIIа group—the state of compensation, the average duration of the T1DM is 0.6 ± 0.2 years; IIIb group—the state of compensation, the average duration of the T1DM is 15.1 ± 5.4 years; IV group—persons with a high risk of developing T1DM. (2) \*Differences in the studied indicator with the control group (I) are statistically significant (p < 0.05); (2) \*\*differences in the studied indicator with the control group (I) are statistically significant (p < 0.01); (3) \*\*\* differences in the studied indicator with the control group (I) are statistically significant (p < 0,001).* 
