ACTIVATION OF GRANULOCYTES MEDIATED BY TOLL-LIKE RECEPTORS IN INVASIVE BACTERIAL INFECTIONS

Osypchuk D. V.

CLINICAL AND EXPERIMENTAL MEDICINE

Scentific article

In this study, we examined the activation of granulocytes mediated by Toll-like receptors (TLR), in the group of children with invasive bacterial infections. Stimulation of TLR2, TLR4, TLR7 and TLR8 led to a significant increase in the expression of integrin CD11b and shedding of adhesion molecules CD62L on granulocytes. Level of spontaneous expression of CD11b integrin in the group of children with invasive bacterial infections was significantly higher — 440,7 ± 177,8 MFI compared with the control group (242,1 ± 94,9 MFI, P < 0,01). Level of spontaneous expression of CD62L was significantly lower compared to control group (45,7 ± 29,6 MFI and 78,3 ± 12,2%, P <0,05, respectively). Study group also characterized by a large variability in the values of the spontaneous expression of CD62L, which, combined with high levels of spontaneous expression of CD11b indicative of an active inflammatory state and confirms the possibility of using these markers as indicators of inflammation. For correct analysis of experimental data, the study group was divided into two subgroups depending on the spontaneous expression of CD62L. The first subgroup (1a) included samples with higher or equal to 35% CD62L+ granulocyte (the lowest rate of CD62L expression in the control group). The 1b subgroup included samples with percentage of CD62L+ granulocytes below 35%. Both subgroups of children with invasive bacterial infections showed significantly higher levels of CD11b expression induced in response to stimulation of TLR2 and TLR4. In the 1a subgroup the expression level reached 755,6 ± 214,5 and 746,07 ± 155 in the 1b subgroup, that was significantly higher compared to control group (P < 0,05). The level of expression of adhesion molecules CD62L upon activation of TLR2 reached the lowest rate in the control group — 4,5 ± 1,9%, which is statistically different from the residual level of expression in the 1a subgroup — 10,1 ± 8,2% (P < 0,05). The level of expression of CD62L in group 1b was 5,3 ± 2,1% and there was no statistical significance compared with other groups. As after incubation with peptidoglycan, levels of CD11b expression after incubation with lipopolysaccharide, in the subgroups 1a and 1b, were significantly higher compared to control group. The highest level of CD62L expression after incubation with lipopolysaccharide was observed in the subgroup 1a — 7,6 ± 5,3%, there was no statistical significance compared with other groups Increased expression of CD11b mediated by activation of TLR2 and TLR4 indicates previous sensitization of bacterial antigens and priming of granulocytes, which is an important prerequisite for full activation of granulocytes. Activation of TLR7/8 that recognize viral ssRNA, led to an increase in integrin expression, but induced expression levels did not differ between the experimental groups. In the first subgroup, the level of residual CD62L expression on granulocytes after activating ligands TLR2 and TLR7/8, was significantly higher than in the control group. Such residual expression of adhesion molecules on granulocytes, once activated, can contribute to enhanced cell migration to sites of inflammation due to tighter contact with the endothelium. Due to the low spontaneous expression of CD62L in subgroup 1b, performance CD62L expression, is activated after inconsistent. Higher levels of induced expression in response to stimulation by bacterial ligands of TLR2 and TLR4, but not TLR8 and TLR7, indicates previous sensitization of bacterial antigens and priming of granulocytes, which is essential for the full activation of immune response.

Toll-like receptors, bacterial infections, granulocytes

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«Bulletin of problems biology and medicine» Issue 1 part 1 (126), 2016 year, 194-198 pages, index UDK 616-022.7- 053.2:616.155.3