B cell–macrophage interactions in colorectal cancer: state coupling, spatiotemporal remodeling, and therapeutic implications

The immune microenvironment of colorectal cancer (CRC) is characterized by pronounced cellular-state and spatial heterogeneity. B cells and macrophages bridge adaptive and innate immunity, respectively, and engage in bidirectional regulation through antibodies and immune complexes, BAFF/APRIL signaling, cytokines, chemokines, and metabolic cues. These interactions are further shaped by tumor cells, stromal components, microorganisms, and other immune populations within the tumor microenvironment. From the perspective of B cell–macrophage state coupling, this review systematically summarizes the biological foundations and reciprocal communication mechanisms underlying their interactions, with particular emphasis on their dynamic remodeling across different disease stages, tertiary lymphoid structures, distinct spatial niches within tumors, and metastatic progression. We further evaluate how established therapies and emerging experimental interventions influence this cellular network. Current evidence suggests that specific B-cell and macrophage states may form distinct functional combinations within either immune-supportive or immunosuppressive ecosystems. However, direct causal evidence remains limited, and the reproducibility of these associations across independent patient cohorts has yet to be firmly established. Future studies should integrate single-cell sequencing, B-cell receptor clonotype tracking, spatial multi-omics, and functional perturbation approaches to move beyond cellular co-occurrence and computationally inferred communication toward direct validation of functional dependencies. Such efforts will also be essential for determining whether composite state–spatial signatures can improve patient stratification, therapeutic response prediction, and treatment decision-making.