TB susceptibility in individuals with type 2 DM

A study investigates the immune responses of individuals with latent tuberculosis infection (TBI) who also have type 2 diabetes mellitus (T2DM), a comorbidity known to increase the risk of developing active tuberculosis (TB). Using the Mycobacterial Growth Inhibition Assay (MGIA), researchers compared the ability of immune cells from individuals with TBI-T2DM and those with TBI but no diabetes (TBI-NDM) to inhibit the growth of Mycobacterium tuberculosis (M.tb). The study also analyzed the cytokine profiles in these two groups, given the importance of type 1, type 17, and IL-1 family cytokines in TB immunity. A total of 34 individuals from Tamil Nadu, South India, participated in the study, with blood samples used for functional assays and cytokine measurements.

The results showed that individuals with TBI-T2DM had a significantly reduced ability to control M.tb growth in vitro, reflected by higher CFU counts compared to their non-diabetic counterparts. Furthermore, several critical cytokines involved in protective immune responses—such as IFNγ, IL-2, TNFα, IL-17, IL-1α, and IL-1β—were found to be significantly lower in TBI-T2DM individuals. These findings suggest a disrupted immune response in diabetics, potentially explaining their increased vulnerability to TB. Interestingly, correlation analyses revealed complex interactions between cytokines, with both positive and negative associations that may play roles in immune regulation and disease progression.

In conclusion, this study demonstrates that T2DM impairs the immune control of latent TB, likely due to dysregulated cytokine responses. These insights could help guide clinical decisions and public health policies, emphasizing the importance of early TB screening and immune monitoring in diabetic patients. The authors call for further research to identify biomarkers that can predict TB progression and improve treatment strategies in this dual-risk population.

Source: Dasan, B., Rajamanickam, A., Pandiarajan, A.N., Shanmugam, S., Nott, S. and Babu, S., 2025. Immunological mechanisms of tuberculosis susceptibility in TB-infected individuals with type 2 diabetes mellitus: insights from mycobacterial growth inhibition assay and cytokine analysis. Microbiology Spectrum, 13(1), pp.e01445-24.