Immunomodulatory effect of traditional Chinese medicine in infectious diseases.

[ETHNOPHARMACOLOGICAL RELEVANCE] Infectious diseases remain a major global public health challenge. Traditional Chinese Medicine (TCM) embodies the medical wisdom of the Chinese nation, developed through thousands of years of practice in combating epidemics and infections. Guided by its unique theoretical system, centered on "Fuzheng Quxie" (Reinforcing Healthy qi and eliminating pathogenic factors, ), TCM approaches health and disease from a holistic and dialectical perspective, which differs fundamentally from conventional Western medicine. Its application reflects distinct ethnic medical characteristics rooted in Chinese philosophy and cosmology, and refined through long-term clinical observation. A growing body of evidence suggests that specific Chinese herbal medicines, traditional Chinese medicinal formulas and their active components exhibit various immunomodulatory properties. Nevertheless, a systematic analysis that considers these effects in the context of both traditional Chinese theory and modern immunology is still required.

[AIM OF THE REVIEW] This review aims to provide a comprehensive analysis of the immunomodulatory effects of specific Chinese herbal medicines, traditional Chinese medicinal formulas and their active components on infectious diseases. It seeks to bridge the underlying theory of these medicines with modern immunology and to evaluate their potential as therapeutic agents and vaccine adjuvants.

[MATERIALS AND METHODS] A systematic literature search was conducted in academic databases, including PubMed and CNKI, to identify relevant studies published in English and Chinese. Articles were selected based on their focus on TCM formulations or natural products used in infectious disease models, with an emphasis on immune-related outcomes.

[RESULTS] Preclinical and emerging clinical evidence suggests that many Chinese herbal medicines, traditional Chinese medicinal formulas and their active components exert multifaceted immunomodulatory effects by regulating key immune pathways and molecular targets, thereby maintaining the body's immune homeostasis and demonstrating promising, yet still largely exploratory, potential for clinical translation. In terms of innate immunity, some TCM formulas can inhibit signaling pathways such as NF-κB/MAPK, reducing the excessive release of inflammatory cytokines including IL-6 and TNF-α, thereby alleviating infection-induced cytokine storms. At the same time, some TCM and their active components can modulate the balance of macrophage M1/M2 polarization, synergistically promoting pathogen clearance and tissue repair. Furthermore, specific TCM helps restore the balance between Th1/Th2 and Th17/Treg, mitigating excessive inflammation or immune dysregulation during infection. In adaptive immunity, specific TCM formulas and active ingredients can upregulate the expression of MHC-II and co-stimulatory molecules such as CD80/86 on dendritic cells, enhancing antigen-presentation efficiency and thereby facilitating pathogen elimination. Some TCM formulas can also increase the CD4/CD8 T-cell ratio, promote the secretion of cytokines such as IL-2 and IFN-γ, and improve T-cell function by modulating immune checkpoint pathways such as PD-1/PD-L1. Meanwhile, specific TCM formulas stimulate B-lymphocyte proliferation and antibody class switching, promoting the production of IgM, IgA, and IgG and thereby enhancing humoral immune responses. Notably, some TCM formulations appear to exhibit bidirectional immunomodulatory properties. These properties suppress excessive inflammatory responses during infection while preserving certain aspects of adaptive immune function. This mechanism may contribute to the therapeutic effects of TCM in combating infections. Some TCM formulas and active ingredients also contribute to post-infection immune reconstruction and can act as a vaccine adjuvant to enhance immunogenicity. Guided by the TCM theory of "Fuzheng Quxie", the immunomodulatory role of TCM and its formulations in infection provide new perspectives and strategies for the clinical prevention and treatment of infectious diseases, holding important scientific exploration value and practical application prospects.

[CONCLUSIONS] The multidimensional immunomodulatory effects of TCM are one of the key mechanisms that make it effective against infections. This review helps clarify the multiple immunomodulatory mechanisms of some TCM formulas and their active components in the prevention and control of infectious diseases, and discusses its potential as a source of novel strategies for addressing major challenges such as antibiotic resistance and emerging infectious diseases.