Cytokines are considered the most important secretions of the immune system that participate in a variety of cellular, inflammatory, and pathogenic processes in human disease. Cytokines that are produced in large amounts and gain across to the circulation act in a hormonal fashion and have drastic effects on other cells. Therefore, the excessive or insufficient production of certain cytokines may contribute to the pathogenicity of certain diseases [1]. An imbalance between pro- and anti-inflammatory cytokines is a well-known characteristic of SLE. Current evidence indicates that cytokine levels are related to systemic lupus erythematosus (SLE). High levels of proinflammatory cytokines may lead to an exacerbation of inflammatory response, apoptosis, and production of autoantibodies that initiate and sustain SLE disease activity [2].

SLE involves immune dysregulation and the production of autoantibodies caused by abnormalities in the activation of the innate and adaptive immune system, the occurrence, severity, and prognosis of which are highly impacted by ethnicity [3]. Certain characteristics of SLE demand the need for further study, including its incidence ratio across genders being 9:1 female to male, and its propensity to occur during the early reproductive years among women, both of which add crucial value to the study of human reproductive immunology [4]. Further studies have also highlighted that female patients present a malar rash, photosensitivity, arthritis, and oral ulcers, while male patients present more often with serositis and renal and immunological disorders. This difference indicates sex-specific features in the pathology of SLE [5].

Women account for more than 80% of SLE cases, making it an autoimmune disease with a hereditary predisposition. SLE can have an impact on the kidney, heart, joints, and central nervous system, among other internal organs [6]. Additionally, lymphopenia, leucopenia, thrombocytopenia, and complement deficiencies (C1q, C2, and C4) are blood abnormalities commonly seen in SLE patients [7]. The main causes of SLE are autoantibodies and immune complex deposition, increased apoptosis, and inadequate apoptotic cell clearance resulting in the production of excessive amounts of autoantibodies. Dysregulated cytokine production, which also contributes to tissue inflammation and organ damage, exacerbates immunological dysfunction. When T and B cells are stimulated, they release a variety of cytokines and autoantibodies that enhance the symptoms of the illness [8].

The haematological manifestation of SLE includes leucopenia, lymphopenia, thrombocytopenia, myelofibrosis, and autoimmune haemolytic anaemia; studying these symptoms is important at different disease stages to assess if the occurrence is due to manifestation of SLE, treatment consequences, or another type of blood cell dyscrasia [9, 10, 11, 12]. There is also a growing body of evidence highlighting the role of cytokines in SLE pathogenesis, including interleukin-6 (IL-6), interleukin-17 (IL-17), interleukin-18 (IL-18), type I interferons, and tumour necrosis factor-alpha (TNF-$\alpha$). Cytokine profiling plays a key role in understanding disease prognosis and aids in devising targeted therapies [13]. Assessing the relationship between haematological indices and cytokines aids in better understanding the pathogenesis of the disease; our study is one such analysis performed among Saudi SLE patients. Our study examines cytokine profiles among SLE patients and healthy controls, specifically focusing on IL-6, interleukin-10 (IL-10), and TNF-$\alpha$ and their roles in haematological abnormalities. The correlation between haematological parameters and the levels of cytokines in patients with SLE is not clearly defined. Evaluating and confirming the correlation between haematological parameters and cytokine levels may help understand the mechanism underlying the development of haematological abnormalities in SLE disease. Therefore, this study aims to understand the correlation between cytokines and haematological abnormalities in Saudi patients with SLE.

The study included a total of 140 Saudi participants, including 100 diagnosed SLE patients and 40 healthy controls, all participants above 18 years (Table 1).

Females were found to be the majority in both the study cohorts, comprising 88% among SLE cases and 85% among the healthy controls. The cohort distribution is outlined in Table 2.

The present study assessed the impact of haematological indices and cytokine profiles among Saudi patients with SLE. The most frequent haematological abnormalities were detected to be anaemia, thrombocytopenia, and leukopenia. Our study also identified significantly high levels of all three cytokines (i.e., TNF-$\alpha$, IL-6 and IL-10) among SLE cases compared to the healthy controls. Elevated cytokines were also found to correlate with multiple haematological indices: Increased levels of TNF-$\alpha$ were correlated with haemoglobin, RBC, HCT, MCV, MCH, MCHC, RDW, and ESR, while elevated levels of IL-6 were correlated with haemoglobin, RBC, HCT, MCV, MCH, MCHC, and ESR. In the case of IL-10, high levels were correlated with haemoglobin, platelet count, and RDW. The reason for the high prevalence of female subjects in the SLE case group (88%) remains unclear, although studies implicate sex hormones, and the upregulation of cytokine-like IFN-$\alpha$ was shown to increase reproductive fitness and simultaneously increase women’s susceptibility to SLE [5].

Haematological abnormalities were reported to be a common occurrence in SLE, with studies reporting the incidence rate to be about 50% due to impaired erythropoietin responses and the development of corresponding antibodies [5]. Other causes of anaemia may include nutritional deficiencies, myelofibrosis, gastrointestinal loss, infection, hypersplenism, treatment-induced illness, etc. [14]. Our study also identified anaemia as the most common haematological abnormality among SLE cases at 52%. Studies on SLE-impacted quality of life have demonstrated an increase in ESR to occur independently of the organic damage index and hence serve as a relevant and sensitive index to determine disease activity. The organ lesion index has also been shown to rise with the occurrence of adverse haematological events including anaemia, leukopenia, and thrombocytopenia, which impair quality of life. Studies thus suggest the importance of a routine assessment of quality of life in SLE to facilitate the early detection of anaemia [15].

Studies have also assessed the prognostic impact of thrombocytopenia, wherein a clinical manifestation the same as that of the first episode was recorded in addition to the classification criteria at diagnosis, immunologic profile, disease activity, and end-organ damage. The study identified 58% of SLE cases with thrombocytopenia at diagnosis, and haemorrhagic manifestations were significantly associated with the degree of thrombocytopenia. The study identified thrombocytopenia to define a subgroup of patients with higher morbidity [16]. Our study identified thrombocytopenia at a much lower frequency than that reported in 8% of cases. The difference in reported frequencies can be attributed to differences in SLE disease activity that were shown to be correlated negatively with platelet counts. This difference is also considered a prognostic factor in identifying cases with an aggressive course of disease [17].

Among the white blood cell (WBC) abnormalities, studies have reported a prevalence of leukopenia in between 22% and 41.8% of cases, lymphopenia in between 15% and 82% of cases, and neutropenia in between 20% and 40% of cases. However, studies on evidence for the risk of infection with lower WBC counts continue to be contradictory [18]. Our study identified leukopenia in 17%, leucocytosis in 4%, neutropenia in 20%, and lymphopenia in 14% of SLE cases. Factors such as the number of cases, region, race, treatment, and research method used may influence the differences in the prevalence of leukopenia, neutropenia, and lymphopenia reported among various studies [19]. The haematological findings of our study also aligned with many previous publications. Levels of haemoglobin were found to be significantly decreased among SLE cases compared to the healthy controls, which is in line with a publication by Yu et al. [20]. A significant increase in ESR and RDW was also detected among SLE cases, as previously reported, wherein an increased RDW was related to active disease status and suggested to be useful as a surrogate marker for inflammation over neutrophil and lymphocyte counts [21, 22, 23]. Our present study also did not detect a significant difference in platelet counts and MPV between SLE cases and healthy controls, while some published reports indicated higher disease activity with a lower MPV [24, 25]. Studies have also assessed individual MPV fluctuations and investigated if these variations could be associated with clinical phenotypes of SLE, finding intra-individual MPV variations to be of low magnitude and disease activity fluctuations to not impact MPV values longitudinally [26].

In the case of cytokine profiling, the present study identified levels of TNF-$\alpha$, IL-6, and IL-10 to be elevated significantly among SLE cases compared to the healthy controls. This finding is in accordance with a recent publication by Jin S et al. [25] who reported levels of serum IL-6, IL-10, and TNF-$\alpha$ in SLE groups to be higher than those in the healthy control group. The study also found the mean course of the disease and IL-10 to be independent prognostic factors of SLE, thus indicating monitoring of serum cytokines to aid in understanding the prognosis of patients with lupus and guide clinical treatment. SLE cytokine networks are crucial in drug development and disease management strategies as imbalances in such networks were correlated with disease progression [27]. Our study reported a negative correlation between levels of IL-6, TNF-$\alpha$, and haemoglobin in SLE patients, while a positive correlation was noted between levels of IL-6, TNF-$\alpha$, and platelet counts. These findings are in line with previous publications highlighting levels of TNF-$\alpha$ and IL-6 to be higher in SLE patients with active haematological disease compared to inactive disease; this association was found to be dependent on inverse correlation. Positive correlations between TNF-alpha, IL-6, and the SLE Disease Activity Index were also recorded [27, 28]. Cytokines including TNF-$\alpha$, IL-6, and IL-10 stimulate the production of hepcidin and inhibit the production of erythropoietin, resulting in anaemia [15]. Thus, the use of IL-6 inhibitors was recommended to correct anaemia in patients with SLE and control disease activity [29].

The current study additionally identified a negative correlation between IL-10 levels and haemoglobin levels in SLE patients, and it also found a positive correlation between platelet counts and SLE patients. However, these findings do not match those previously reported, which instead indicated that levels of IL-10 do not correlate with haematologically active disease in SLE cases [30]. Recent studies have also indicated that IL-10 plays a dual role in SLE, wherein it inhibits pro-inflammatory effector functions and is also the main driver of the extra follicular antibody response [31]. Ethnicity has also been reported to play a role in determining the concentration of IL-10 and was found to be different between various ethnic groups. For example, Asian SLE cases were found to have more than twice the concentration of serum IL-10 compared to non-Asian cases [32].

Investigating the correlation between the proinflammatory cytokines and hematological abnormalities among SLE patients in a Saudi Arabian population provides insights into how the interplay between cytokines and hematological abnormalities may differ in this specific ethnic and geographic context. Genetic, environmental, and lifestyle factors can vary between populations, potentially leading to unique patterns in disease manifestation and progression. Additionally, conducting this research in Saudi Arabia has the potential to uncover unique insights and contribute to the global understanding of SLE and its associated hematological abnormalities. It can also have practical implications for healthcare and treatment strategies in the Saudi Arabian context.

Moreover, the hematological profiles of patients with SLE can vary among individuals and populations, including those from different ethnicities. Whether the hematological profiles of Saudi Arabian SLE patients are similar to or different from those of other ethnicities worldwide can depend on various factors, including genetic, environmental, and healthcare access factors. Nearly the same results were recorded by [27] as they examined the levels of TNF-alpha, TNF receptors, IL-6, and IL-10 in individuals with SLE. To the best of our knowledge, they addressed these factors in Egyptian patients, and it involved a limited number of patients [27, 29].

Multiple regression analysis was also performed to assess the relationship between haematological abnormalities and increased cytokine levels. Levels of haemoglobin and ESR were shown to be associated with both TNF-$\alpha$ and IL-10. Haemoglobin, MCV, MCH, MCHC, and RDW were also associated with IL-6. Studies have also demonstrated the IL6-hepcidin–haemoglobin axis to be non-functional during lupus flare cycles, as serum hepcidin was not found to rise with increased renal or extra-renal lupus activity [33]. Therefore, the association between haematological abnormalities and increased levels of cytokines could be useful markers in predicting SLE and assessing disease activity [20]. Studies that assessed changes in the levels of cytokines in SLE cases and their clinical value found the mean course of the disease and IL-10 to be independent prognostic factors for SLE [28].

Our study revealed a modified cytokine pattern in Systemic Lupus Erythematosus (SLE) patients. Specifically, compared to healthy controls, we observed a substantial elevation of TNF-a, IL-6, and IL-10 levels in Saudi patients with SLE. Moreover, this increase was closely associated with the activity of SLE. Among individuals with SLE, hematological irregularities were identified as the most prevalent. In addition, the connection between cytokine patterns and hematological parameters suggests that cytokines play a significant role in the emergence of these hematological irregularities. Cytokines in their pathogenesis could potentially contribute to early diagnosis and the formulation of more targeted therapies for SLE. However, it is crucial to emphasize that additional research is needed to gain a more comprehensive understanding of how these cytokines may impact the development of anemia in SLE.

All data generated or analysed during this study are included in the published article. The original contributions presented in the study are included in the article/Supplementary material, further inquiries can be directed to the corresponding author.

Conceptualization, FMA; methodology, FMA and MAA; formal analysis, MAA; investigation, FMA and MAA; resources, FMA; data curation, FMA and SAA; data interpretation, AFA, KHD and RS; writing—original draft preparation, FMA and MAA; writing—review and editing, FMA, MAA, SAA, AFA, KHD, and RS; supervision, FMA; funding acquisition, FMA. All authors read and approved the final manuscript. All authors have participated sufficiently in the work to take public responsibility for appropriate portions of the content and agreed to be accountable for all aspects of the work in ensuring that questions related to its accuracy or integrity. All authors contributed to editorial changes in the manuscript.

The current study received approval from the Institutional Review Board (IRB) at King Saud University (Research Project No: E-19-3701). This study was also approved form IRB at Saudi Arabian Ministry of Health (IRB NO: 2019-0054M). In addition, all study participants contributed to this study were applied assigned and written informed consent.

The authors extend their appreciation to the Researchers Supporting Project number (RSP2023R506) at King Saud University, Riyadh, Saudi Arabia.

This research was funded by King Saud University, Riyadh, Saudi Arabia (RSP2023R506).

The authors declare no conflict of interest.