Association of increased neopterin production with decreased humoral immunity in the elderly.

Tetanus toxoid (TT) antibodies of 447 adult persons aged 27-69 years were investigated and analyzed in relationship with the time span since the last vaccination against tetanus as well as the serum concentration of neopterin. Neopterin is a pteridine, which is produced by monocytes/macrophages upon stimulation with the type 1 T cell-derived cytokine interferon-gamma. There was an inverse correlation between serum neopterin and TT antibody concentrations (Spearman's rank correlation coefficient: r(s)=-0.259; p<0.0001) which was even stronger when persons with neopterin concentrations and TT antibodies below the third quartile of the study population were excluded (residual group: n=210; r(s)=-0.718; p<0.0001). The study demonstrates that an immunoregulatory shift towards type 1 immunity as indicated by higher neopterin concentrations coincides with lower TT antibody concentrations in the elderly.