The endocannabinoid system has emerged as an important modulator of immune responses, contributing to the regulation of inflammation, immune activation, and immune tolerance (17). Among its components, CB1R and CB2R play distinct roles within the immune system. CB2R is preferentially expressed in immune cells and has been associated with immunoregulatory and predominantly anti-inflammatory functions, whereas CB1R, although primarily described in the nervous system, is also detectable in peripheral immune cells in a context-dependent manner (19). Despite increasing interest in the immunological functions of cannabinoid receptors, their characterization in human autoimmune diseases remains limited (17, 24–26). SLE is an autoimmune disease characterized by dysregulated immune responses involving altered B-cell activation, impaired immune tolerance, and changes in T-cell function. Evidence on cannabinoid receptor involvement has been limited (3). Previous studies have reported the presence of CNR1 and CNR2 mRNA in peripheral blood mononuclear cells from patients with SLE, as well as correlations between CNR2 transcript levels and complement components C3 and C4; however, these approaches do not provide information on receptor expression at the protein level or within defined immune cell subsets (27).

In this study, we addressed this gap by providing a comprehensive immunophenotypic characterization of CB1R and CB2R expression across major B- and T-lymphocyte subsets in patients with SLE. By integrating univariate analyses with high-dimensional and multivariate approaches, we show that alterations in cannabinoid receptor expression in SLE are not uniformly distributed across the immune system. Instead, our results consistently identify the B-cell compartment as the major contributor to group differentiation between patients and healthy controls, with CB2R expression emerging as a dominant feature across multiple stages of B-cell differentiation. In contrast, changes in CB1R expression were more heterogeneous and extended to both B- and T-cell subsets but contributed less strongly to group discrimination in multivariate models. Notably, however, CB1R-associated variables showed a higher degree of association with clinical features, suggesting a potential link between CB1R expression patterns and clinical heterogeneity within SLE, whereas CB2R expression primarily reflects broader immunophenotypic differences between groups.

The preferential involvement of the B-cell compartment is particularly relevant in the context of SLE, where B cells contribute to disease pathogenesis not only through autoantibody production but also by acting as antigen-presenting cells and by shaping T-cell responses via cytokine secretion (28). The observation that CB2R expression was increased across naïve, transitional, regulatory, memory, and plasma cell subsets suggests that cannabinoid signaling pathways may be engaged throughout multiple stages of B-cell differentiation in SLE.

In other autoimmune and inflammatory conditions, increased CB2R expression in immune cells has frequently been interpreted as a response to sustained immune activation, consistent with experimental evidence showing anti-inflammatory and immunomodulatory effects following CB2R engagement (29–33). Within this framework, elevated CB2R expression in B cells has been proposed to reflect an attempt to restrain excessive immune activation and to promote immune homeostasis in chronically inflamed environments. These findings are consistent with in vitro studies demonstrating anti-inflammatory effects mediated by CB2R activation, including inhibition of T-cell recruitment, reduced Th1/Th2 polarization, decreased T-cell proliferation, and increased T-cell apoptosis after CB2R agonist stimulation (34–40). CB2R activation has also been shown to modulate B-cell migration, promote B-cell expansion, enhance retention of immature B cells in bone marrow, and increase CB2R expression within germinal centers (41–45). Although this evidence is not directly related to the altered receptor expression observed in the present study, it further suggests the functional relevance of CB2R in immune regulation. In this context, our findings raise the possibility that altered CB2R expression in SLE may be associated with immunoregulatory processes across B-cell subsets; however, given the disease-specific immune dysregulation that characterizes SLE, functional studies in this context are required to determine whether this expression patterns translate into mechanistic or clinically relevant effects.

In immune-mediated diseases characterized by impaired tolerance, sustained overexpression of receptors involved in survival, activation, or differentiation pathways may paradoxically contribute to disease persistence by altering activation thresholds or promoting the survival of autoreactive cells. Under such conditions, signaling pathways that are homeostatic under physiological circumstances may become maladaptive when chronically engaged. This context-dependent interpretation of CB2R signaling is illustrated by observations from other disease settings. In melanoma, higher CB2R expression has been associated with improved survival and increased intratumoral B-cell infiltration, while experimental models have shown that CB2R deficiency impairs B-cell development and differentiation (42, 46). These findings are consistent with a role for CB2R in B-cell survival and functional competence under physiological or antitumor immune conditions.

In contrast, in autoimmune diseases such as SLE, where peripheral B-cell tolerance is already compromised, similar signaling pathways may have different consequences (1). Chronic engagement of receptors involved in B-cell survival and activation can favor the persistence of autoreactive clones, as exemplified by BAFF overexpression in SLE, which enables naïve and transitional autoreactive B cells to escape anergy and negative selection (1, 28, 47). In this setting, the widespread increase of CB2R expression observed across early and mature B-cell subsets may be compatible with a dysregulated engagement of pathways that are otherwise homeostatic, potentially contributing to immune persistence rather than resolution. However, this interpretation remains hypothetical and requires functional validation in the context of SLE.

Following the identification of clear group-level differences between patients with SLE and healthy controls, we next examined the relationship between cannabinoid receptor expression and clinical features within the SLE cohort. In these analyses, multiple immune variables were associated with disease-related clinical parameters, including disease activity, remission status, hemoglobin levels, and specific organ involvement. Among clinical measures, SLEDAI and remission status were those most consistently associated with laboratory features. Higher SLEDAI scores were specifically associated with a polarized receptor expression pattern characterized by reduced CB1R expression and increased CB2R expression across multiple B-cell subsets, most prominently within transitional and memory compartments. Remission status showed substantial overlap with these associations, while additionally encompassing a subset of immune variables unique to the remission profile.

The strength of these findings is supported by multivariate analyses, including VIP scores and ROC curve evaluation. CB2R expression in Bm2, Bm2’, and naive B cells emerged as key contributors to group differentiation, not only between patients and controls but also between active and remission states. These subsets showed high AUC values within this dataset, suggesting their potential relevance in distinguishing disease activity. Although these findings point to candidate immunophenotypic profiles, they should be interpreted as exploratory and require validation in independent cohorts.

These clinical correlations can be interpreted in the context of previous observations on endocannabinoid signaling dynamics in SLE. Alterations in ligand availability and receptor expression appear to coexist with disease activity, rather than remaining static features of the disease. Elevated circulating levels of 2-arachidonoylglycerol (2-AG), a full agonist of both CB1R and CB2R, have been reported in patients with SLE, with higher concentrations observed in individuals with lower disease activity (27). This pattern suggests a potential relationship between endocannabinoid signaling and disease activity; however, the functional implications of this association remain to be fully elucidated.

CB1R expression has been less studied in SLE; however, studies in other immune-mediated conditions provide contextual information regarding its potential role. In type 1 diabetes, increased CB1R expression has been reported in CD4⁺ T cells and pancreatic β cells, and CB1R blockade has been shown to reduce Th1 polarization (48). Notably, in murine models of cutaneous SLE, CB1R agonists have demonstrated potent anti-inflammatory effects, reducing clinical manifestations, histological damage, and systemic cytokine levels (49). In vitro studies further suggest a role for CB1R in immune regulation, as its activation has been associated with a reduced Th1 response, decreased T-cell migration and proliferation, increased apoptosis, and downregulation of activation markers (40). In this framework, the reduced CB1R expression observed in patients with higher disease activity in our study may be associated with a more permissive environment for immune activation. At the same time, upregulation of CB2R in B-cell subsets may reflect a concurrent response to sustained immune activation, consistent with its proposed role in modulating immune responses in inflammatory settings. These observations support a context-dependent immunomodulatory effects of endocannabinoid receptor expression in SLE, although the functional implications of these observations in human disease are not yet fully understood.

In addition, cannabinoid receptor expression was also associated with specific clinical domains. Hemoglobin levels correlated predominantly with CB1R-expressing B-cell subsets, suggesting a possible association between CB1R expression and systemic inflammatory features in SLE, although the underlying mechanisms remain unclear.

Organ-specific associations also suggest that cannabinoid receptor expression patterns may vary across different clinical manifestations of SLE. Articular involvement was associated with higher CB2R expression in CD4⁺ effector and central memory T cells, whereas mucosal involvement correlated with reduced CB2R expression across multiple T-cell populations, suggesting that distinct inflammatory milieus may be associated with differential engagement of cannabinoid receptor pathways. Finally, the association of regulatory T cells with cannabinoid receptor expression highlights the possibility that ECS dysregulation in SLE may extend beyond effector compartments and may influence immunoregulatory balance.

These results should be interpreted in an exploratory context, as the relatively small sample size and cross-sectional design limit causal inference and generalizability. Although multiple comparisons across immune cell subsets were controlled using FDR correction, the possibility of residual false-positive findings cannot be excluded. Therefore, these findings should be considered hypothesis-generating and require validation in independent and longitudinal cohorts.

Finally, the observed associations between cannabinoid receptors expression and clinical parameters support the relevance of the endocannabinoid system as a potentially important immunoregulatory pathway in SLE. Our findings expand the current understanding of cannabinoid receptor expression across immune cell subsets in human disease and highlight the B-cell compartment as a major site of altered receptor expression. In addition, the associations identified with disease activity and clinical manifestations suggest that cannabinoid receptor expression patterns may have potential relevance as candidate immunological markers and warrant further investigation in functional and longitudinal studies.