The ability of peripheral blood mononuclear cells (PBMC) of syphilitic patients to produce IL‐2

The cell‐mediated immune response of importance in protection against Treponema pallidum , is distinctly suppressed in some stages of the disease. This may be a result of decreased ability of cells to produce IL‐2, or IL‐2 absorption by different factors. The experiments were designed to evaluate the ability of peripheral blood mononuclear cells (PBMC) of patients with different stages of syphilis to produce IL‐2, and to investigate the causes which could possibly limit its activity. The ability of the PBMC of syphilitic patients to produce IL‐2 develops at the beginning of the disease, reaching a maximum in primary seropositive syphilis. In the next stages of the disease this capability is distinctly lowered. The lowest was in malignant syphilis and tabes dorsalis, i.e. during severe disease. Absorption of adherent cells from PBMC increased the ability of lymphocytes to produce IL‐2. The highest level of this interleukin was observed at the stages of the disease where suppression was the deepest. Sera of both control and syphilitic patients contained IL‐2 inhibitor. Its level was the highest in early and late latent syphilis where no symptoms of disease were present. In all syphilitic sera a distinctly elevated level of soluble IL‐2 receptors (sIL‐2R) was also found. Its high level was noted in sera of patients in which PBMC had the weakest ability to produce IL‐2. These findings suggest that sIL‐2R may be bound to IL‐2 and in this way would lead to weakening of T cell function and of resistance against Treponema pallidum infection.