To assess whether determination of 38 F-64 F specific antibody responses could be useful for monitoring the efficacy of chemotherapy, a series of serum samples were obtained from active TB patients who had undergone anti-TB chemotherapy for 0–6 months at one month interval and the serum levels of all of three isotype antibodies, i.e., IgG, IgM and IgA, specific to 38 F-64 F, were determined. This evidence concerns the gene CD40LG and tuberculosis.