DYNAMICS AND ZONAL DISTRIBUTION OF CD68⁺ MACROPHAGES IN THE RAT INGUINAL LYMPH NODE DURING POST-TRAUMATIC REGENERATION

INTRODUCTION. Soft tissue trauma initiates a complex cascade of immune responses in regional lymph nodes (LNs). Macrophages (CD68⁺ cells) play a key role in these processes.
OBJECTIVE. To identify patterns in the dynamics and zonal distribution of CD68⁺ macrophages in the rat in-guinal LN at various time points after soft tissue injury.
MATERIALS AND METHODS. The experiment was performed on 50 mature male Wistar rats (weight 220–250 g). A model of soft tissue injury to the thigh was used. Animals were euthanized on days 1, 3, 7, and 14 after trauma (10 animals per time point), with the control group (n=10) consisting of intact rats. In the LNs, CD68⁺, CD3⁺, CD19⁺, Ki67⁺, bcl-2⁺, and p53⁺ cells were detected in 8 structural and functional zones: cortex (C), pri-mary lymphoid nodules (PLN), secondary lymphoid nodules (SLN), paracortical zone (PCZ), medullary cords (MC), subcapsular marginal sinus (SMS), perinodular sinus (PNS), and medullary sinus (MS). Statistical analy-sis was performed using nonparametric methods: Kruskal–Wallis test, Dunn's test, Spearman's correlation analysis, Jonckheere–Terpstra test, cluster analysis, and multiple regression (R environment 4.3.2).
RESULTS. Heterogeneity in the dynamics of CD68⁺ macrophages was revealed depending on the LN zone. Maximum changes were recorded in the PCZ on days 3 and 7, followed by a subsequent decrease. In the SMS, the peak also occurred on day 3, with a sharp drop in macrophage count observed on day 1, likely related to their migration deeper into the node. In the MC, maximal accumulation of CD68⁺ cells were noted on day 3, with subsequent normalization by day 14. The MS demonstrated a consistently elevated level of CD68 from day 3 to day 14. Correlation analysis revealed strong associations of CD68 with CD3⁺ T cells in the PCZ (r=0.81; p<0.001) and with CD19⁺ B cells in the MC (r=0.77; p<0.001), as well as with the proliferation marker Ki67 (r=0.88 in the PCZ) and with p53 in the SMS (r=0.84; p<0.001). The regression model confirmed that the main predictors of CD68 accumulation in the PCZ were CD3⁺ cells (β=0.62; p<0.001) and proliferating lympho-cytes (β=0.48; p<0.001). Cluster analysis divided the zones into three groups according to the pattern of CD68 dynamics: highly reactive (PCZ, SMS), moderately reactive (MC, MS), and inert (C, PLN, and SLN).
CONCLUSION. The macrophage response exhibits a strictly zonal and phase-dependent pattern. The PCZ functions as a command center where macrophages cooperate with T lymphocytes to initiate the adaptive immune response. The SMS serves as the «entry gate», where macrophages undergo apoptosis after antigen processing. The MC acts as an effector field where macrophages support plasmablastic transformation of B cells. The revealed heterogeneity in the response of different LN zones underscores their functional speciali-zation and should be considered when interpreting immunomorphological changes.

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