Dynamics of CD40 ligand levels in newly diagnosed and treated tuberculosis patients: An evaluation of sCD40L concentration and CD4+ T cell surface expression

Background/objectiveCD40 ligand (CD40L/CD154), a member of the TNF superfamily, plays a critical role in immune regulation. Primarily expressed on CD4+ T cells, the CD40-CD40L interaction is essential for B-cell activation, antibody production, and isotype class switching. CD40L expression on T cells has been linked to Mycobacterium tuberculosis (MTB)-stimulated IFN-γ production by peripheral blood mononuclear cells. This study aimed to determine the serum concentration of soluble CD40L (sCD40L) and its surface expression on CD4+ T cells in newly diagnosed tuberculosis (TB) patients and in TB patients undergoing anti-tuberculosis treatment (ATT) for 2–3 months.Materials and methodsNinety-two subjects infected with MTB were recruited and divided into two groups; Group I consisted of 46 newly diagnosed TB patients without prior treatment, and Group II included 46 TB patients receiving ATT for the last 2–3 months. Serum sCD40L concentration of each participant was measured using ELISA, while its surface expression on CD4+ T cells was analyzed via flow cytometry.ResultsSerum sCD40L levels were significantly lower in (Group I) newly diagnosed TB patients (median = 11.1 ng/mL, IQR = 1.19–20.8) compared to (Group II) patients undergoing ATT (median = 17.4 ng/mL, IQR = 8.9–27.8), with a statistically significant difference between the groups (p = 0.000). The surface expression of CD40L on CD4+ T cells was also lower in Group I (median = 2.9, IQR = 0.16–13.99) compared to Group II (median = 3.22, IQR = 0.01–12), though the difference was not statistically significant (p = 0.893).ConclusionNewly diagnosed TB patients exhibited reduced levels of sCD40L, which increased following 2–3 months of anti-tuberculosis treatment. These findings suggest that CD40L may play a role in the immune response to tuberculosis and that its levels are modulated by treatment.