Warm AIHA, accounting for 60-70% of adult cases and approximately 50% of pediatric cases, is characterized by IgG autoantibodies with optimal binding at physiological temperature (∼37°C) ( Table 1 ) (6). In the affected individuals, DAT is typically positive for IgG, and in most cases, the autoantibodies are polyclonal and directed against a range of erythrocyte antigens. The principal target is band 3 (SCL4A1), a major transmembrane anion exchanger. However, reactivity is frequently observed against other antigens, including Rh, Jk, Kell, Gerbich, Wright, glycophorin A and D, and Landsteiner-Wiener (7).

Hemolysis in warm AIHA predominantly occurs via extravascular mechanisms localized to the spleen and, to a lesser extent, the liver. Three principal immune effector pathways contribute to erythrocyte destruction ( Figure 1 ): (1) antibody-dependent cellular phagocytosis (ADCP), (2) antibody-dependent cellular cytotoxicity (ADCC), and (3) complement-dependent cytotoxicity (CDC) (8). In the first two processes, the spleen serves as the primary site of extravascular hemolysis and the generation of autoreactive plasma cells, which sustain autoantibody production and contribute to hemolysis (9). Opsonized RBCs are recognized and phagocytized by red pulp macrophages via Fcγ receptors (FcγRs) IIa and IIIa (10). Among the IgG subclasses, FcγRs exhibit the highest affinity for IgG1 and IgG3 compared to IgG2 and IgG4 (11). Notably, splenic macrophages also express FcγRIIb, an inhibitory receptor whose activation may underlie the limited efficacy of intravenous immunoglobulin (IVIG) therapy in AIHA, as IVIG is thought to exert its effects, at least in part, through interactions with FcγRIIb (12). Natural killer (NK) cells and neutrophils, which express Fcγ receptors, can also mediate ADCC (13).

Although complement activation is generally less prominent in warm AIHA than in IgM-mediated cold AIHAs, IgG1 and IgG3 autoantibodies retain the capacity to activate the classical complement cascade through C1q binding. Following C1q engagement, conformational changes in the C1 complex (C1q, C1r, and C1s) initiate sequential proteolytic cleavage of C4 and C2 into C4a, C4b, C2a, and C2b, culminating in C3 convertase formation and downstream activation of the terminal complement cascade. This may result in variable degrees of intravascular hemolysis, although it typically remains a minor component compared to extravascular mechanism (14).

Cold AIHA accounts for 20–25% of cases and is primarily driven by complement-mediated hemolysis. In these cases, DAT positivity is restricted to C3, and high-titer cold agglutinins exhibit optimal reactivity at low temperatures (typically 4–10°C) ( Table 1 ) (15). A key distinction exists between cold agglutinin syndromes (CAS) associated with an underlying disorder and primary cold agglutinin disease (CAD), recently redefined as a clonal B-cell lymphoproliferative disorder in the 5th edition of the World Health Organization (WHO) classification (16). Specifically, CAD occurs in a clinically significant monoclonal gammopathy, where a clonal B-cell population produces auto-reactive IgM antibody. In contrast, in infection-associated CAS, IgM autoantibodies are usually polyclonal and less pathogenic than monoclonal ones (17).

In CAD/CAS, IgM autoantibodies primarily target the I antigen, which emerges on the erythrocyte membrane in adults following the enzymatic conversion of the fetal i antigen by β1,6-N-acetylglucosaminyltransferase (18). The pentameric nature of IgM promotes red cell agglutination, causing RBC aggregates that impair microcirculation in acral regions, where temperatures may fall within the thermal range permissive for agglutination even in the absence of environmental cold exposure ( Figure 1 ) (19). Indeed, disease severity is primarily determined by the thermal amplitude of IgM rather than its serum titer, with a high thermal amplitude (>28°C) allowing for effective antibody binding even at normal body temperature (19). Notably, IgMκ binding to the erythrocyte surface in CAD induces agglutination and hemolysis by activating the classical complement pathway. Opsonization of RBCs by C3b promotes their extravascular clearance, primarily mediated by hepatic macrophages (20). However, terminal complement activation with membrane attack complex (MAC) C5b-C9 formation is generally absent during stable clinical phases and occurs predominantly during acute exacerbations or in severe disease (20, 21).

Paroxysmal cold hemoglobinuria (PCH) is a rare and challenging entity within the spectrum of AIHA, accounting for less than 5% of cases and with an estimated annual incidence of 0.04 per 100.00 individuals (22). PCH is mediated by the Donath-Landsteiner antibody, a biphasic IgG that targets the RBC surface P antigen. Specifically, the Donath-Landsteiner IgG binds to its antigen at low temperatures and fixes early complement components C1, C4, and C2; upon warming to 37°C, the classical complement pathway is further activated, resulting in C3 cleavage and progression to terminal complement activation, which leads to acute intravascular hemolysis (22, 23). This pathogenic mechanism is unique among AIHA subtypes and contrasts with the primarily extravascular hemolysis observed in warm AIHA and CAD/CAS.

Historically, PCH was described as a chronic or recurrent complication of congenital or tertiary syphilis. The widespread use of penicillin led to a dramatic decline in syphilitic PCH, and the condition has since been reported predominantly in children following upper respiratory tract infections (24). However, recent epidemiological trends indicating a resurgence of syphilis underscore the need to reintegrate syphilis-associated PCH into the differential diagnosis of AIHA, including in adult patients (24).

Thrombosis is a major contributor to morbidity and mortality in AIHA, with both arterial and venous events occurring in 10–20% of cases (25–29). Retrospective data from 378 AIHA patients reported a 15% prevalence of venous thromboembolism (VTE), with warm AIHA and atypical variants carrying the highest risk (26). Notably, thrombotic rates appear consistent across different etiologies (30). Both a decade-long retrospective analysis and a Danish population-based study revealed a twofold increase in VTE risk in AIHA patients compared to non-AIHA controls (27, 28). Key risk factors include active hemolysis (hemoglobin ≤8 g/dL, elevated LDH), anemia severity, and prior splenectomy, emphasizing the role of hemolysis intensity in driving thrombosis (25, 29).

The classical coagulation model as a linear proteolytic cascade has evolved into a more integrated framework, incorporating the interplay between hemostasis, innate immunity, and the complement system (31). This revised paradigm is particularly relevant to AIHA, where intravascular hemolysis, complement activation, and inflammatory signaling converge to establish a prothrombotic state. While the mechanisms of hemolysis are well-characterized (32), emerging evidence provides novel insights. Mannes et al. (33) demonstrated that adenosine diphosphate (ADP), released upon MAC-dependent erythrocyte lysis, contributes to platelet activation and thrombotic propagation, in line with the pro-inflammatory role of damage-associated molecular patterns (DAMPs), such as heme ( Figure 1 ) (31). Erythrocyte-derived extracellular vesicles (EVs), enriched in phosphatidylserine and tissue factor, have been implicated in AIHA-associated hypercoagulability. Barcellini et al. (34) found that EV levels were elevated in hemolytic patients, showing a correlation with the severity of anemia. Notably, patients with AIHA had much higher EV counts than healthy controls. Beyond hemolysis and erythrocyte-derived DAMPs, complement activation emerges as a key driver of the prothrombotic environment. A bidirectional interaction between complement and coagulation has been described (35), where complement activation enhances coagulation and vice versa through multiple mechanisms. C3 directly binds to fibrin, stabilizing clots and increasing resistance to fibrinolysis (36). Moreover, MAC activation on platelets at sublytic levels induces the externalization of procoagulant phospholipids, amplifying thrombin generation (37). Complement activation also drives the release of C3a and C5a, potent anaphylatoxins that recruit inflammatory cells and sustain thrombogenic inflammation (38). Conversely, thrombin cleaves C5 and C5b into non-canonical fragments that promote highly lytic MAC formation, linking coagulation and complement in a self-perpetuating cycle (35). These findings suggest that thrombotic risk in AIHA is not solely driven by hemolysis but reflects complex interactions between complement, platelets, and inflammation. This crosstalk underscores the rationale for complement-targeted therapies to mitigate thrombosis and improve clinical outcomes in AIHA.

Historically, autoimmunity has been attributed to the interplay between genetic predisposition and environmental triggers, including infections, medications, or concomitant diseases, which together drive the emergence and clonal expansion of autoreactive lymphocytes ( Figure 1 ) (39). In AIHAs, a known mechanism is molecular mimicry, where foreign antigens share structural or functional similarities with self-proteins, triggering cross-reactive immune responses. Notably, Herpesviridae (e.g., EBV, CMV, Varicella-Zoster virus) and Poxviridae exhibit a significantly higher degree of linear peptide homology with human proteins than other viral families, supporting their role in immune dysregulation (40). This concept gained attraction during the COVID-19 pandemic, as autoimmune cytopenias emerged in SARS-CoV-2-infected patients (41). Angileri et al. (42) identified an immunogenic epitope (LLLQY) shared between the RBC cytoskeletal protein ANK-1 and the SARS-CoV-2 spike glycoprotein, providing direct evidence of viral-induced AIHA (43). Beyond mimicry, viruses may further drive autoimmunity by exposing cryptic intracellular antigens upon cell lysis (44).

A similar mechanism may underlie drug-induced immune hemolytic anemia (DIIHA), where drug-dependent autoantibody formation occurs through immune-allergic hypersensitivity or non-immunologic protein adsorption (45). Among drugs commonly associated with AIHA, furosemide, antibiotics (e.g., amoxicillin, ceftriaxone, cefixime, cefpodoxime, ciprofloxacin, amphotericin B, sulfamethoxazole/trimethoprim, norfloxacin), azathioprine, NSAIDs (e.g., ibuprofen), and paracetamol have been implicated, with azathioprine carrying the highest associated risk (46).

While T-cell dysregulation has been a dominant focus, recent attention has shifted back to B-cell involvement, particularly the concept of a “forbidden clone”, an autoreactive B-cell population that escapes immune tolerance checkpoints, fueling persistent autoantibody production (47). Whether autoimmunity precedes or follows B-cell clonal expansion remains debated. Epidemiologic data show an increased risk of Non Hodgkin lymphomas (NHL) in patients with preexisting autoimmune diseases such as celiac disease and rheumatoid arthritis, supporting a two-hit model in which loss of immune tolerance precedes oncogenesis through chronic inflammation, persistent antigenic stimulation, and genetic susceptibility (48). Conversely, B-cell malignancies can drive autoimmunity via humoral and cellular dysregulation, as seen in hypogammaglobulinemia and altered regulatory T-cell subsets, underscoring the bidirectional link between lymphoproliferation and immune dysregulation (49). This is exemplified in AIHA associated with chronic lymphocytic leukemia (CLL), characterized by autoreactive polyclonal B cells alongside neoplastic monoclonal B cells (49).

The involvement of autoreactive lymphocyte clones is well established in warm AIHA and CAS; however, recent insights have refined the pathogenic understanding of CAD. Although overt lymphoid malignancy is typically absent, most CAD patients harbor a monoclonal IgMκ B-cell population, indicative of an underlying lymphoproliferative disorder ( Figure 1 ). Randen et al. (50) delineated a clinically and immunophenotypically homogeneous entity in a cohort of 54 CAD patients. Bone marrow examinations revealed nodular infiltrates of mature B cells, lacking distinct morphological features, negative for the MYD88 L265P mutation, and not fulfilling diagnostic criteria for lymphoplasmacytic lymphoma (50). This evolving paradigm redefines CAD as a distinct disorder, separate from other lymphoproliferative neoplasms, thereby sustaining its pathogenic framework and inclusion in the latest WHO classification.

Susceptibility to autoimmune diseases, including AIHA, is influenced by genetic variants that modulate immune responses. Given the critical role of the human leukocyte antigen (HLA) system, studies have focused on polymorphisms in specific HLA loci that alter the selection and activation of autoreactive T lymphocytes. Notably, HLA-B8 and BW6 alleles have been associated with an increased risk of AIHA, suggesting their involvement in the persistence of autoreactive lymphocyte clones (51). Additionally, specific immunoglobulin heavy-chain variable (IGHV) gene configurations appear to promote the selection of autoreactive B-cell clones (52, 53). For instance, IGHV4-34, IGHV4-31, IGHV3-23, and IGK3–20 gene rearrangements have been found in CAD patients (54–56). Moreover, genetic variants such as the G polymorphism in CTLA4 and the AG configuration in the lymphotoxin-α gene have been reported at higher frequencies in AIHA patients (57, 58).

In CAD, next-generation sequencing (NGS) has revealed gene mutations affecting B- and T-cell function. Notably, mutations in KMT2D, which encodes a histone methyltransferase involved in B-cell survival, differentiation, and homing, are present in 69% of cases. In contrast, mutations in CARD11, a key regulator of the NF-κB signaling pathway, are detected in 31% (59). Emerging candidate genes include IGLL5, whose precise role in B-cell development remains under investigation, and CXCR4, which plays a critical role in B-cell migration and trafficking (60). Additionally, decreased expression of CR1, a negative regulator of B-cell activation and differentiation, has been reported in CAD (56). The genetic contribution is even more pronounced in pediatric Evans syndrome (pES), a condition characterized by AIHA, immune thrombocytopenia, or autoimmune neutropenia (61). In a cohort of 80 pES patients, 40% were found to harbor mutations in immune-regulatory genes such as TNFRSF6, CTLA4, STAT3, PIK3CD, CBL, ADAR1, LRBA, RAG1, and KRAS (62).

Moreover, the role of polymorphisms in inflammatory cytokines has gained recent attention, further elucidating the complex genetic and immune dysregulation underlying AIHA. Specifically, Zaninoni et al. (63) identified single-nucleotide polymorphisms (SNPs) in genes encoding TNF-α, TGF-β1, IL-10, IL-6, and interferon γ (IFN-α), showing associations with disease severity and treatment response. In line with Pavkovic et al. (64), AIHA patients exhibited a lower frequency of the TNF-α -308 G/A polymorphism compared to controls, as well as a reduced genotypic frequency of TNF-α -308 G/A and TGF-β codon 25G/C. The genetic link with cytokines was further emphasized in pES, where PTPN2 haploinsufficiency has been identified, contributing to heightened sensitivity to cytokine signaling through the JAK/STAT pathway (65).

Self-tolerance is a fundamental principle of immune homeostasis, essential for preventing aberrant autoreactive responses ( Figure 1 ). In the thymus, central tolerance serves as the primary checkpoint for T lymphocyte selection and is coordinated by medullary thymic epithelial cells, cortical thymic epithelial cells, dendritic cells, and thymic B cells (66). These cells mediate antigen presentation and the clonal deletion of autoreactive T lymphocytes. Thymocytes expressing T cell receptors (TCRs) that fail to engage self-peptides presented via major histocompatibility complex (MHC) molecules undergo death by neglect due to insufficient survival signaling (67). Despite these mechanisms, up to 40% of autoreactive T cells and a comparable fraction of autoreactive B cells evade central tolerance (68, 69). Peripheral regulatory networks act as additional safeguards to limit their activation and expansion. These include T cell anergy, mediated by inhibitory receptors such as CTLA-4, clonal deletion via Fas-Fas ligand interactions, and suppression by CD4+/CD25+/Foxp3+ regulatory T cells (Tregs), which exert immunomodulatory effects through cytokines such as interleukin 10 (IL-10) and TGF-β (66, 70, 71).

T cells play a pivotal role in the pathogenesis of AIHA, contributing to the breakdown of immune tolerance and to the production of anti-erythrocyte autoantibodies. Unlike other self-reactive T cells, those targeting RBC antigens escape thymic negative selection. Instead, CD4+ recent thymic emigrants (RTEs) encounter RBCs in the periphery, where they modulate inhibitory receptor expression, particularly programmed death cell 1 (PD-1), and transcription factors associated with anergy, functional exhaustion, and regulatory differentiation (72). This dynamic suggests that tolerance to RBC autoantigens is primarily maintained through peripheral rather than central mechanisms.

In murine models, an imbalance between T helper 1 (T_H1) and T helper 2 (T_H2) subsets has been described, with a predominant T_H1 response characterized by elevated IFN-γ production. Disease improvement in these models occurred in response to the T_H2 cytokine IL-4 (73, 74). Conversely, human warm AIHA has traditionally been classified as a T_H2-driven disorder, as indicated by elevated IL-4 levels and reduced IFN-γ secretion (75). Moreover, like other autoimmune diseases, AIHA seems to be marked by an imbalance between effector T cells and Tregs (76). The pathogenic role of T helper 17 (T_H17) cells has been well documented in multiple inflammatory disorders (77), and an elevated presence of T_H17 cells has been observed in AIHA patients, strongly correlating with disease activity (78). In murine models, dysfunction in CD4+/CD25+ Tregs impedes autoimmunity suppression, facilitating the production of erythrocyte autoantibodies (79). Recently, Ciudad et al. (80) observed a shift favoring T_H17 polarization within T effector cells, associated with elevated serum IL-17 levels, aligning with findings by Xu et al. (78). Additionally, a reduction in circulating Tregs and decreased Foxp3 expression, a key transcription factor for Treg stability and suppressive function, were noted (80). Consistent with these observations, interference with RTE tolerance mechanisms using immune checkpoint inhibitors led to a concurrent decline in Foxp3+ Tregs and an increase in T_H17 cells (81).

CD39 single-positive CD4+ T cells emerged as a predictive marker for AIHA development, suggesting their direct involvement in tolerance breakdown. CD39, an ectonucleotidase that hydrolyzes ATP and other extracellular nucleotides, modulates the immune microenvironment. Its dysregulation may contribute to the expansion of proinflammatory T cells, particularly T_H17, while concurrently reducing regulatory populations, thereby promoting an autoimmune response against erythrocytes (81).

Increasing attention is given to the roles of follicular helper T cells (T_HF) and follicular regulatory T cells (TFR) in autoimmune pathogenesis and erythrocyte hemolysis. T_HF cells play a central role in complex regulatory events within the germinal center, including germinal center formation, B-cell support, isotype switching, high-affinity antibody production, and memory cell differentiation (82). In this setting, IL-6 and IL-21 contribute to T_HF differentiation and function by upregulating the transcriptional repressor BCL6. In AIHA, a murine study reported increased levels of both T_HF and TFR cells alongside elevated IL-21 and IL-6 levels. The pathogenic involvement of these subsets was further confirmed by the adoptive transfer of purified CD4+/CXCR5+/CD25− T_HF cells from immunized mice, which induced autoantibody production in an AIHA murine model (83). Similarly, 24 patients with pES exhibited increased circulating T_HF cells, heightened T-cell activation, and a reduction in naïve CD4+ T cells compared to healthy controls and patients with chronic immune thrombocytopenia (84). Post-activation exhaustion features were also noted, with upregulation of canonical checkpoint inhibitors, and a higher degree of β-chain oligoclonality in the TCR was observed in T_HF cells compared to healthy controls.

Following B-cell activation and differentiation within secondary lymphoid organs and inflamed tissues, a subset of plasma cells migrates to bone marrow niches, where they persist as long-lived plasma cells (LLPCs), comprising approximately 25% of the total bone marrow plasma cell pool (85). These CD38⁺/CD138⁺/CD20^- cells are responsible for sustained long-term antibody production, a function that can persist for decades (86). Their survival is regulated by stromal and immunoregulatory signals from dendritic cells, stromal cells, and regulatory T cells, which, through molecules such as CD80/86, CXCL12, and B-cell activating factor (BAFF), promote their persistence (86). At the molecular level, LLPCs overexpress anti-apoptotic genes (MCL1, BCL2, BCL-XL), making them highly resistant to immune-mediated depletion (87).

In warm AIHA, persistent autoantibody production is driven by autoreactive plasmablasts and plasma cells, with circulating plasmablasts indicating ongoing B-cell activation (9). Once settled in the spleen and bone marrow, LLPCs become refractory primarily to conventional therapies, including corticosteroids, rituximab, and other immunosuppressive agents targeting CD20-positive B cells. This limitation in therapeutic efficacy is particularly relevant in steroid-refractory or relapsing AIHAs, where ongoing autoantibody production by LLPCs sustains hemolysis despite the effective depletion of peripheral B cells (9). Moreover, it has been observed that B-cell depletion-induced alterations in the splenic microenvironment create a dependency of plasma cells on BAFF and CD4+ T cells. This suggests that the expression profile of LLPCs is influenced by signals derived from the splenic microenvironment (88).

Precise classification of AIHA subtypes is essential to tailor treatment strategies and predict clinical outcomes. AIHA should be suspected in patients presenting with anemia and laboratory evidence of hemolysis, with the DAT serving as the primary diagnostic tool to confirm the immune-mediated nature of hemolysis ( Table 1 ) (89, 90). The DAT detects immunoglobulin and/or complement bound to RBCs by using reagents that bind these components and induce visible agglutination in vitro (91).

The DAT-tube has traditionally been performed using polyspecific antiglobulin reagents, which yield semi-quantitative results without differentiating antibody isotypes or thermal amplitude. The composition of these reagents can vary significantly in the proportion of anti-IgG, anti-IgM, anti-IgA, and anti-complement components, often favoring anti-IgG (92). This approach can lead to false-negative results in cases involving IgA antibodies, low-affinity autoantibodies, or when the number of IgG molecules bound to RBCs falls below the assay’s detection threshold. The use of monospecific DAT enables accurate identification of specific autoantibody classes, thereby enhancing differential diagnosis and informing more precise therapeutic strategies (2, 15, 93) Additionally, employing low ionic strength solutions (LISS) or cold washes can overcome DAT negativity. Although less specific, more sensitive methods such as microcolumn and solid-phase antiglobulin tests allow for detection of low levels of IgG coating RBCs (93).

Among the most diagnostically challenging variants of AIHA, PCH warrants particular attention. The diagnostic process in PCH is often complex and far from straightforward (22). The DAT usually reveals isolated C3d positivity, which may also be observed in other complement-mediated forms of AIHA (22). Definitive diagnosis relies on the Donath-Landsteiner test, a technically demanding assay that is not routinely available outside of specialized laboratories (94). Therefore, clinicians should consider PCH in patients presenting with acute hemolysis and hemoglobinuria, especially when typical warm or cold autoantibody patterns are absent (22, 23).

A detailed clinical history is essential to exclude alternative causes of hemolysis or confounding factors, such as recent transfusion reactions, drug-induced hemolysis, or glucose-6-phosphate dehydrogenase (G6PD) deficiency, which is more prevalent in specific populations (95). Evaluation should also include assessment for underlying disorders, particularly systemic autoimmune diseases (e.g., systemic lupus erythematosus) and lymphoproliferative malignancies like CLL or indolent NHL (90). Patient age can inform diagnostic considerations, with younger individuals more likely to present with underlying infections or autoimmune diseases, while older patients have an increased likelihood of harboring an active neoplastic disorder. Notably, infection screening is warranted when patients present with recent fever or respiratory symptoms; testing for EBV infection is particularly relevant in children and young adults (3). Signs such as weight loss, lymphadenopathy, hepatosplenomegaly, lymphocytosis, or cytopenias should prompt investigation for lymphoproliferative disorders.

Beyond standard hemolytic markers, extended immunohematologic and biochemical workup is essential to distinguish primary from secondary forms of AIHA (90, 96). Although this distinction is not immediately critical, since first-line treatment generally follows the same approach as for primary AIHA, it becomes clinically relevant when an underlying disorder requires targeted management (97). Autoantibody panels that include antinuclear antibodies (ANA), extractable nuclear antigens (ENA), anti-DNA, and antithyroid antibodies, should be considered in patients with suggestive clinical features such as arthralgias, serositis, or thyroid dysfunction. These tests may uncover an underlying connective tissue disease, guiding the use of immunosuppressants or targeted biologics (90). Moreover, in patients with a history of thrombotic events or recurrent abortion, antiphospholipid antibody testing is advisable. Viral serologies are also recommended (98). Serum protein electrophoresis, immunofixation, and quantitative immunoglobulin assays can help identify cases associated with plasma cell dyscrasias, such as Waldenström macroglobulinemia (99), or with primary immunodeficiencies (100). Bone marrow evaluation, including morphologic, histopathologic, immunophenotypic, and cytogenetic analysis, is essential for diagnosing AIHA associated with lymphoproliferative disorders, myelodysplastic syndromes, or marrow failure syndromes (90). This is particularly important at diagnosis in patients with CAD and in relapsed warm AIHA patients who are corticosteroid-refractory (90). Additionally, total-body computed tomography (CT) scanning is fundamental for staging and identifying lymphadenopathy or splenomegaly, which may indicate underlying lymphoid malignancies.

Several therapeutic strategies that directly target B cells involved in autoantibody production ( Figure 2 ) have been explored. These approaches aim to counteract relapse and treatment resistance, often driven by the persistence and escape mechanisms of autoreactive B cells at different stages of maturation. Among B-cell-directed therapies, targeting the B-cell receptor (BCR) signaling pathway is particularly relevant, given its central role in lymphoproliferative disorders and autoimmune diseases. The BCR regulates B-cell survival, proliferation, and activation through a complex intracellular signaling network involving Bruton tyrosine kinase (BTK), phosphoinositide 3-kinase (PI3K), and spleen tyrosine kinase (SYK) (103). The following sections explore these therapeutic strategies, evaluating their mechanisms of action, clinical efficacy, and limitations in the context of B cell-mediated autoimmunity.

Complement activation is a central driver of hemolysis in AIHA, particularly in CAD, where it mediates intravascular destruction and extravascular clearance of erythrocytes (2). Beyond hemolysis, excessive complement activation contributes to a procoagulant and inflammatory environment, exacerbating disease severity and increasing thrombotic risk. As shown in Figure 3 , these pathogenic effects highlight the classical complement pathway as a critical therapeutic target, with emerging inhibitors showing promise in mitigating hemolysis and its systemic complications.