Intracellular tubulo-reticular structures of peripheral blood mononuclear cells as an ultra-structural marker of disease activity in systemic lupus erythematosus: a pilot study.

Objective: Under physiological stress, the membranes of organelles undergo conformational change to tubulo-reticular structures (TRS) for gaining survival advantage. We aim to explore whether TRS formation in the peripheral blood mononuclear cells (PBMCs) of patients with systemic lupus erythematosus (SLE) correlates with more active disease where physiological stress prevails.

Methods: To mimic the intracellular impact of interferon-alpha (IFN-α) on lymphocytes, human B-lymphocyte cell line was stimulated by recombinant IFN-α in concentrations of 100, 1000 and 10 000 IU/mL for 72 h. TRS within the lymphocytes was then quantified by transmission electron microscopy (TEM). Upon confirming TRS formation under IFN-α influence, PBMCs of lupus patients were isolated, fixed and quantified for TRS under TEM. The frequency of TRS in lupus PBMCs was compared with that of healthy controls and correlated with the clinical SLE disease activity index (SLEDAI).

Results: After 72 h, an increase in TRS frequency was observed in a dose-response fashion when the human B-lymphocyte cell line was stimulated by increasing concentrations of IFN-α. In lupus patients, their PBMCs had a significantly higher TRS frequency than healthy controls (P = 0.037). The frequency of TRS was positively associated with the SLEDAI (Spearman ρ = 0.632, P = 0.012), which remained statistically significant after adjustment for daily prednisolone dose (Pearson r = 0.747, P = 0.002).

Conclusions: While the clinical significance of TRS formation in lupus PBMCs deserves further investigation, these preliminary findings suggest a significant relationship between the disease severity of SLE and intracellular physiological stress. These results underscore the potential of TRS in PBMCs as an ultra-structural disease activity biomarker of SLE.