Evaluation of the Percentage of Monocyte Subpopulations with TLR2 and TLR4 Expression About Selected Skin Functional...

Background/Objectives: Acne vulgaris can be non-inflammatory lesions, i.e., closed comedones, open comedones, inflammatory lesions, i.e., papules, pustules, cysts, and post-acne lesions. This study aimed to evaluate the expression of TLR2 and TLR4 receptors on classical, intermediate, and non-classical monocyte subpopulations in 38 women with acne vulgaris and to correlate the results with clinical features of the disease and selected skin parameters. Methods: The skin parameters were assessed: level of oiliness, hydration, pH, skin pigmentation (phototype, erythema) using a special diagnostic device (Scientific multi-probe system MPA 6, Courage + Khazaka) with simultaneous determination of monocyte subpopulations in peripheral blood expressing TLR2 and TLR4 using a CytoflexLX flow cytometer (Beckman Coulter). Results: In the study group, the percentage of non-classical monocytes expressing TLR2 was statistically significantly lower than the classical and intermediate monocytes expressing TLR2 (p < 0.001). However, the level of TLR2 receptor expression (MFI) was significantly higher on intermediate monocytes compared to the level of TLR2 expression on classical and non-classical monocytes. In the group of patients with post-acne lesions, a statistically significantly higher percentage of non-classical monocytes with TLR4 expression was observed compared to patients without post-acne lesions (p = 0.009). A statistically significant negative correlation was also observed between the percentage of intermediate and non-classical monocytes with TLR4 expression and the results of the mexameter measurements. Acne has a significant impact on the percentage of monocyte subpopulations expressing TLR2 and TLR4. A higher percentage of non-classical monocytes TLR4+ in the blood is associated with a higher incidence of post-acne lesions. Conclusions: The positive correlation between the degree of skin hydration and the level of TLR2 expression on classical monocytes suggests that these cells play an important role in skin homeostasis and defense against C. acnes. Proper acne care is not only important for aesthetic aspects, but may also have a positive impact on immunological phenomena.