Why Immunogenicity Is the Core Issue in Stem Cell Therapy
Umbilical cord-derived MSCs offer structural advantages in immunogenicity — but the optimal cell source depends on the disease and treatment strategy
Stem cell therapy discussions often center on which cells have the greatest regenerative capacity. But for real-world clinical application, an equally important question is: how strongly does the immune system recognize those cells as foreign? This property is called immunogenicity.
High immunogenicity means transplanted cells are more readily recognized and may trigger inflammatory or rejection responses. Low immunogenicity means the cells are less likely to be attacked — though “low immunogenicity” does not mean “no immune response.” Stem cells are biological entities, and immune reactivity varies with the infusion environment and the patient’s immune status.
Stem Cell Classifications and Clinical Context
Stem cells discussed in regenerative medicine are broadly grouped into embryonic stem cells, induced pluripotent stem cells (iPSCs), and adult stem cells. Embryonic and iPSCs face ethical concerns and oncogenic risks that limit clinical use. Adult stem cells are easier to isolate and culture, have lower immunogenicity, and are the focus of most ongoing clinical and mechanistic research.
Among adult stem cells, mesenchymal stem cells (MSCs) are the most widely studied. MSCs adhere to plastic, express CD105, CD73, and CD90, lack CD45, CD34, and HLA-DR, and can differentiate into adipocytes, chondrocytes, and osteocytes.
The therapeutic effect of MSCs is not explained solely by engraftment and differentiation into new cells. Contemporary research attributes much of the benefit to the MSC secretome — growth factors, immunomodulatory cytokines, antioxidants, and extracellular vesicles that exert anti-inflammatory, anti-apoptotic, extracellular matrix-modulating, and neuroprotective effects in a paracrine manner.
Comparing Cell Sources: Bone Marrow, Adipose, and Umbilical Cord
The tissue of origin matters significantly for immunogenicity.
Bone marrow-derived MSCs have the longest clinical track record. They retain advantages in musculoskeletal applications, bone and cartilage regeneration, and autologous strategies. However, harvest requires an invasive procedure, and cell number, proliferative capacity, and differentiation potential decline with age.
Adipose-derived MSCs are accessible via liposuction or minor surgery. Their secretory profile is enriched in VEGF-A, angiogenin, bFGF, NGF, and HGF — making them particularly suited to angiogenesis, wound healing, and ischemic tissue recovery via paracrine mechanisms. Their multilineage differentiation capacity is comparatively lower.
Umbilical cord-derived MSCs stand out for immunogenicity. Cord tissue is obtained from discarded post-natal material, making harvest non-invasive and ethically uncontroversial. They express very low or negligible levels of HLA class I and II, the primary triggers of allogeneic immune rejection.
The Deuse et al. (2011) Head-to-Head Comparison
This advantage was directly demonstrated by Deuse et al. (2011), who compared umbilical cord intima-derived MSCs (clMSC) with bone marrow MSCs from donors over 65 (bmMSC). The clMSCs showed lower HLA class I expression, produced more immune-tolerizing factors (TGF-β, IL-10), proliferated faster, and triggered weaker allogeneic lymphocyte activation and in vivo immune responses than bmMSCs.
This should not be read as “umbilical cord MSCs cause no immune response.” The same paper notes that MSCs are not fully immune-privileged and can be recognized and cleared by the immune system. In immunocompetent mice, both cell types were eventually eliminated — bmMSCs more rapidly, clMSCs with comparatively longer persistence.
UC-MSCs in Rheumatoid Arthritis and Diabetes
A rheumatoid arthritis review (Lv X et al., 2021) also identifies low immunogenicity as a key advantage of UC-MSCs. These cells express low MHC I and no MHC II, reducing rejection risk, while offering stronger proliferative and differentiation capacity and easier ex vivo culture compared with bone marrow or adipose MSCs. They modulate multiple immune cell populations — T cells, B cells, dendritic cells, NK cells — suppressing Th17 responses and elevating Treg frequencies.
A diabetes review (Li L et al., 2023) presents a similar picture. Human umbilical cord MSCs (HUC-MSCs) are abundant, ethically uncomplicated, low-infection-risk, highly proliferative, and carry very low immunogenicity. Proposed mechanisms include homing to the injured pancreas, paracrine effects via growth factors, cytokines, and exosomes, differentiation into insulin-secreting cells, β-cell protection and regeneration, and anti-inflammatory immunomodulation.
The Off-the-Shelf Opportunity
These properties carry special weight for allogeneic therapy development. Autologous cell therapy avoids rejection but is limited by cell quality in elderly or chronically ill patients and requires individualized collection and culture — adding time and cost. Allogeneic umbilical cord MSCs, derived from healthy neonatal tissue and manufactured under standardized conditions, can be stored until needed, enabling off-the-shelf therapeutic products.
Limitations and Open Questions
That said, “immunogenically favorable” is not the same as “best for every indication.” For bone or cartilage regeneration where specific tissue formation is central, bone marrow MSCs may be more appropriate. Where angiogenesis or wound healing is the priority, adipose MSC secretion characteristics can be advantageous. For immune-mediated, inflammatory, or metabolic diseases where anti-inflammatory and immunomodulatory effects are most important, umbilical cord MSCs become the most compelling candidate.
Repeat dosing and long-term safety remain open questions. How the immune system responds to repeated allogeneic cell infusions, whether antibody formation or accelerated cell clearance develops over time, and what this means clinically — these require long-term studies. “Low immunogenicity” is an advantage, not a license for unlimited repeat dosing.
High proliferative capacity also has two sides. It favors large-scale production and standardization, but quality can shift with culture conditions, passage number, and manufacturing processes. Genetic stability, tumorigenicity, and long-term safety must be systematically evaluated. In metabolically complex diseases like diabetes, the disease environment itself may alter MSC immunomodulatory function.
Conclusion: A More Precise Question
Immunogenicity in stem cell therapy is not merely a laboratory metric — it is a determinant of whether a product can actually be used in the clinic. Umbilical cord MSCs hold comparative advantages in low immunogenicity, strong immunomodulation, high proliferative capacity, and feasibility of standardized manufacturing for allogeneic use.
But the future of stem cell therapy lies not in finding one “best” cell, but in matching the optimal cell source to the disease mechanism and patient context. The right question is not “which stem cell is best?” The right question is: “what cell source best fits this patient, this disease, and this therapeutic goal?”
The competitive strength of cell therapy will ultimately rest not only on biological potential, but on safety, consistency, and predictability.
Umbilical cord-derived MSCs hold a structural edge in allogeneic cell therapy development, owing to low HLA/MHC expression and strong immunomodulatory properties. But there is no single 'best' cell source — UC-MSC fits immune-mediated diseases, bone marrow MSC fits bone and cartilage regeneration, and adipose MSC fits angiogenesis-dependent indications.
Deuse T, et al.; Li L, et al.; Lv X, et al.."Immunogenicity of UC-MSC; HUC-MSC in diabetes; UC-MSC in rheumatoid arthritis." Cell Transplantation; Int J Med Sci; Drug Des Devel Ther, 2011